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░░░░░░▄ ░░░▄ ░░▄ ░░░░░░▄ ░░▄ ░░▄ ░░░░▄ ░░░░░░▄ ░░█▀░░█ ░░░░▄░░█ ░░█▀▀ ░░█ ░░█ ░░█▀▀▀ ░░█▀░░█ ░░░░░░█ ░░█░░░░█ ░░█ ░░░░░░▄ ░░█ ░░█ ░░█░░░▄ ░░░░░░█ ░░█▀░░█ ░░█ ░░░█ ░░█ ▀▀▀▀▀▀ ░█ ░█▀ ░░█ ░░█ ░░█▀░░█ ░░█ ░░█ ░░█ ░░█ ░░░░░░▄ ░░█▀ ░░░░█▀ ░░█ ░░█ ▀▀ ▀▀ ▀▀ ▀▀ ▀▀▀▀▀▀ ▀▀ ▀▀▀▀ ▀▀ ▀▀ ░░░░░▄ ░░░░░░▄ ░░░░▄ ░░█▀░░▄░░█▀░░█░░█▀░░▄ ░░█ ░░█░░█ ░░█░░█ ▀▀ ░░█ ░░█░░█ ░░█░░█ ░░▄ ░░▄ ░░░░░█▀░░░░░░█ ░░░░█▀ ▀▀ ▀▀▀▀▀ ▀▀▀▀▀▀ ▀▀▀▀ (English documentation) ┌─────────────────────────────────────────────┐ │ ANIVGA │ │ a Sprite-Unit for TurboPascal V6.0 │ │ by Kai Rohrbacher │ │ Version 1.0 │ └─────────────────────────────────────────────┘ Purpose : Animation of sprites on a VGA's 320x200x256 mode and TurboPascal V6.0 Author : Kai Rohrbacher Germany Internet: S_ROHRBACHER@IRAVCL.IRA.UKA.DE FIDO : 2:241/7503 Language : TurboPascal V6.0 Date : May 1991 --------------------------------------------------------------------- Always remember: "I know my English spelling is bad, but if I used my own language you probably couldn't read it at all." -- Nico de Vries --------------------------------------------------------------------- 0. Table of contents ──────────────────── 1. Prélude: Legal Notices 2. What is VGA? 3. Features and Restrictions of ANIVGA 4. "HELLO WORLD" - A First Example 5. How ANIVGA works 6. Tips, tricks and techniques 7. Credits 8. ANIVGA Reference Manual 1. Prélude: Legal Notices ───────────────────────── Okay, the boring stuff first... The author hereby disclaims all warranties relating to this software, whether expressed or implied, including without limitation any implied warranties of merchantability or fitness for a particular purpose. I will not be liable for any special, incidental, consequential, indirect or similar damages due to loss of data/damage to hardware or any other reason, even if I have been advised of the possibility of such damages. This programming toolkit is released as "freeware" by the author. It is however copyrighted and all rights and ownership are kept with the author. You may use it, copy it and give it to everybody as long as no modifications are made -- but don't try to sell it (or part of it)! Nevertheless, all programs you realize with this software package may be distributed freely - the only thing I ask you for is to mention the use of this toolkit in your program and to send me a copy of your program. 2. What is ANIVGA? ────────────────── ANIVGA is a powerful toolkit for the animation of sprites on any IBM (or com- patible) with a VGA card installed. It consists of one (big) TurboPascal V6.0-unit to be used by your applications and some utilities to simplify its use: ANIVGA.PAS - the source code of the animation unit MAKES.EXE - a simple spritemaker program (requires a mouse) GRAB.EXE - a TSR-program to "grab" sprites from other graphics UNLIB.EXE - a utility to break apart a library of sprites back into its individual sprite files DUMP_SPR.EXE - a "sprite dumper" which disassembles a (binary) sprite file into an ASCII-text *.* - documentation, examples, ... Copy these files into your TurboPascal-directory and compile ANIVGA.PAS to implement ANIVGA on your system - that's all. 3. Features and Restrictions of ANIVGA ────────────────────────────────────── Some of ANIVGA's features are: - flickerfree animation by a "page-flipping" algorithm and using the vertical retrace signal - sprite movement in any increments you want - arbitrary background image for the animation - full use of the VGA's 256-color mode - several sprite display methods available: - sprites can be written normally (covering underlying figures) - sprites can be declared to be transparent with regard to the background or other sprites pixel by pixel - sprites can change their color depending on the underlying background image (-> shadow function) - display methods can be different for each sprite - pixel precise hit-detection routine built in - correct clipping of sprites at the screen boundaries - up to 32767 different sprites - up to 500 sprites may be simultaneously active - maximal size of each sprite = 64k - maximal size of all loaded sprites only restricted by available memory - works with virtual coordinates in the range -16000..+16000 - thus simple creation of horizontal/vertical "scrolling" games - scrolling background image, too - several supporting routines to: drawing lines (with built in clipping- algorithm), points and graphic-text (incl. clipping), automatic heap management for loading of sprites, sprite libraries, background images, processor-speed adjustment,... What ANIVGA does _not_ support: - EMS or XMS memory (too slow) - resolutions other than 320x200x256 (compatibility question) 4. "HELLO WORLD" - A First Example ────────────────────────────────── ANIVGA uses a non-standard 320x200x256 graphic mode, different from the BIOS- mode $13, but there should be no problems with all truly compatible VGA cards. To see if ANIVGA is compatible with your system and to get a first impression of its ease of use, compile the following simple program (you can find it on disk as file "EXAMPLE1.PAS"): (Remember to copy and compile ANIVGA.PAS in your TurboPascal-Unit-directory first) PROGRAM Example1; USES ANIVGA,CRT; CONST LoadNumber=42; {why not 42? - A "hello" to all Douglas Adam fans!} SpriteName='FLOWER.COD'; {Path and name of the sprite to load} Sprite1=0; Sprite2=5; VAR ch:CHAR; collide:BOOLEAN; BEGIN IF loadSprite(SpriteName,LoadNumber)=0 THEN BEGIN CloseRoutines; WRITELN('Error: '+GetErrorMessage); halt(1) END; InitGraph; Color:=66; BackgroundLine(0,0,XMAX,0); BackgroundLine(XMAX,0,XMAX,YMAX); BackgroundLine(XMAX,YMAX,0,YMAX); BackgroundLine(0,YMAX,0,0); BackgroundOutTextXY(100,70,'Hello world!'); SpriteN[Sprite1]:=LoadNumber; SpriteX[Sprite1]:=0; SpriteY[Sprite1]:=0; SpriteN[Sprite2]:=LoadNumber; SpriteX[Sprite2]:=XMAX SHR 1; SpriteY[Sprite2]:=YMAX SHR 1; WHILE KeyPressed DO ch:=ReadKey; Animate; REPEAT collide:=Hitdetect(Sprite1,Sprite2); if collide THEN BEGIN Sound(1000); Delay(5); NoSound END; if KeyPressed THEN BEGIN WHILE KeyPressed do ch:=UpCase(ReadKey); CASE ch OF 'I':DEC(SpriteY[0]); 'J':DEC(SpriteX[0]); 'K':INC(SpriteX[0]); 'M':INC(SpriteY[0]); 'A':DEC(StartVirtualX,10); 'S':DEC(StartVirtualX,10); END; IF POS(ch,'IJKMAS')>0 THEN Animate; END; UNTIL ch='Q'; CloseRoutines; END. (Don't worry if you do not understand the whole program at once - it should only give you a first impression of ANIVGA's capabilities) If you run this program (make sure that the sprite file FLOWER.COD can be found by the program!) you should see a graphic consisting of two flowers, a rec- tangle showing the screen boundaries and the words "Hello world" near the middle of the screen. You can move the top left flower by using the keys "I","J","K","M". If you hit the other flower with the first one, the program will beep. Try out what happens if you move across the two words in the middle: obviously, the two leafs of the sprite behave somehow different: the black parts of left leaf are "transparent" in that the writing shines through it, while the black parts of the right leaf are "covering black". But the writing (which is written in the background image) won't be destroyed. As soon as you leave them, the words will be alright again. Move the sprite to the very left screen boundary - and move it even more to the left: you'll get the impression that it moves off the screen until it is totally offscreen. Hmmmm - how do we get it back? Sure, "K" will do, but press "A" instead: this will "pan" the whole screen 10 pixels to the left (think of that as if you could control an imaginary camera to slide to the left), "S" pans into the other direction (note the restriction of the program to non-scrolling back- ground at this point: the big rectangle and the words "Hello world" won't move because they are part of the so-called "static" background image). Now -using the "I","J","K" and "M" keys- bring back your sprite to the 2nd one and let them collide. Press "A" a few times to scroll them both offscreen. As you'll notice, the program will not stop beeping: it indicates that the two sprites collide, even if they are not visible to you! Okay, that should be enough for a first impression, so hit "Q" to quit the program, if you've finished wondering... :-) Run EXAMPLE2.PAS for a demonstration of "scrolling" background; the program is much the same as EXAMPLE1, but uses four different "tiles" to build the back- ground image. As before, you can use "I,J,K,M" to move your sprite along, but this time, you may scroll the whole scene (incl. the background!) with the "E,S,D,X" keys, too ("Q" quits, as before). EXAMPLE3.PAS shows (an extremely) simple use of the "Display_SHADOW" mode to display a graphical object: a sprite is used for its own shadow zone, simply by redrawing it with a little horizontal and vertical offset. Although this is a nice trick with many sprites (you don't have to design extra shadow sprites this way), it doesn't always work: note that there is one area in the flower which differs from what we would expect as shadow: this is because ANIVGA assumes that everything between the left- and rightmost point of a sprite belongs to the sprite's interior and will be drawn accordingly. (To circumvent this, one would have to draw one (or even several) especially designed "shadow zone" sprites for the flower, but we'll come to these aspects later) Pressing "P" draws 1000 randomly distributed points so you can better see the shadowing effect for single points. Finally, "C" copies part of the screen into memory (with GetImage() ) and pastes it somewhere else (with PutImage() ) while clipping off at the screen boundaries. EXAMPLE4.PAS is an example how to use "sprite cycles": there are six images in the sprite (library) file HANTEL.LIB which become "glued" together to form one sprite cycle. App. one hundred copies of this sprite are then animated on the screen with maximum animation speed and again, you can scroll the whole screen area with the keys "E","S","D","X". When you do, you will note that as more and more of the sprites gets scrolled offscreen, the remaining sprites will rotate faster. Pressing the space bar will toggle between fastest animation (no time limit) and an animation rate of 200ms per frame. You can play around with this value to find out an "optimal" time for your PC and this program: very small: program will show the same symptoms as mentioned above (being faster for every sprite offscreen) . . . very big : program will slow down even when all sprites are onscreen Somewhere between lies a value where the animation doesn't get slowed down when all sprites are onscreen (=max. work for ANIVGA), but stays at the same speed for all other cases (=less work for ANIVGA). 5. How ANIVGA works ─────────────────── (It would be _impossible_ trying to cope every detail of ANIVGA, but I'm sure you will get the basic ideas of ANIVGA very soon.) As already mentioned, the program uses a "tweaked" VGA-graphic mode: the VGA is programmed in a way to give 4 graphic pages at a resolution of 320x200 pixels in 256 colors ("they said it couldn't be done, but here it is!..."), numbered 0..3. Page 0 and 1 are used for the display, page 2 holds the "normal" background image and page 3 can contain so-called "tiles" which can be used to build a huge background image in "scrolling" background mode. The basic idea of the "page flipping" scheme used is that: do everything (era- sing the old graphic page, draw sprites/lines/pixels/text) on a graphic page invisible to the user while showing him a completed page on the screen. Then, if finished, "flip" the page, thus making the new, completed page visible and the old page to the invisible one. Now start creating the next image on this new invisible page - and so on. "Erasing" the old image means: overdraw it completely with the background image stored in page 2 (or 3), so one could write in pseudo code: ... REPEAT show page 0 to user; fill (invisible) page 1 with contents of page 2; draw new sprites and all other stuff on page 1; show page 1 to user; fill (invisible) page 0 with contents of page 2; draw new sprites and all other stuff on page 0; UNTIL DOOMSDAY ... You as the programmer doesn't have to think much about this mechanism, the routines keep track of the page flipping automatically: the global variable "PAGE" always holds the number of the page which is invisible (and thus: the page to be drawn on). Therefore, we say that PAGE holds the "actual page" number and 1-PAGE is the page visible to the user. Most of the procedures and functions of the animation package adjust themselves to the appropriate page; there are only a few situations where you have to be aware of this mechanism, mostly when drawing pixels or to create special effects. The whole package is "table driven". That means, the interface to the user consists of some tables in which you specify your sprites to be drawn: You store into this tables which sprites to draw ("SpriteN[]") and their coordinates (in "SpriteX[]" and "SpriteY[]"). After this, a call of the main routine "Animate()" gives back control to the animation routines, which update the graphic screen accordingly: ... REPEAT update SpriteN[]-table: deactivate sprite i by storing a "0" into SpriteN[i] or activate a sprite k by storing k in an unused SpriteN[]-entry or let all the other SpriteN[]-entries as they were last cycle FOR ALL SpriteN[i]<>0 DO IF SpriteN[i] should change its coordinates THEN update (SpriteX[i],SpriteY[i]) accordingly call Animate() to draw image and display it UNTIL end-of-computer-life ... You should notice that there are two kinds of "sprite numbers" which should not be mixed up: one is a spriteLOAD number and represents a handle to the (physical) sprite data, while the other (normally termed "sprite number") is a logical number to address this sprite data. In the pseudo code given above, "k" is the spriteLOAD number (it is a number given at load time) and the index "i" in SpriteN[i] is the sprite number. Note that "k" is a unique value: you can think of it as a NAME of the sprite data loaded (e.g. you could name the FLOWER.COD - data as "123" when loading it: there can't be another sprite with the same LOAD-number). On the other hand, there could be a hundred flowers on the screen: just choose hundred different sprite-table entries (=sprite numbers), e.g. SpriteN[100].. SpriteN[199] and store "123" in each of them! Whenever you are unsure if you (or I) are speaking of a "sprite number" or a "spriteLOAD number", remember that: ■ A sprite number can hold values in the range 0..NMAX and is an index of the tables SpriteX[], SpriteY[] and SpriteN[]. ■ A spriteLOAD number can hold values between 0..LoadMax and is assigned as a "name" to the sprites' physical loaded data; a "0" as load number is reserved for "inactivate sprite" The world ANIVGA knows is 32000 pixels wide and high, numbered -16000..+16000 on each axis. Because your graphic screen consists of only 320 by 200 points, (ranging from 0..XMAX and 0..YMAX in the x- and y-axis, respectively; (0,0) is the upper left corner, (XMAX,YMAX) the lower right one) you can only see a small part of this world, but ANIVGA does not distinguish between the visible and invisible parts of the world. If, for example, two sprites collide, the routine "HitDetect()" will find out, even if this collision occurs offscreen. Thus you can think of your graphic display being a "camera" to the real world: your actions can take place everythere in this virtual world, but you see only the part displayed by your camera; if you wish to see another part of your world, you have to move this imaginary camera to that place. In ANIVGA, you can do this by changing the values "StartVirtualX" and "StartVirtualY" which hold the upper left corner of the visual window. As an example, let (StartVirtualX,StartVirtualY) be (1000,500): then on your screen you will see the part of the world which ranges from coordinates (1000..1319) and (500..699) in X- and Y-directions, respectively. 6. Tips, tricks and techniques ────────────────────────────── There would be a lot of things to say and most of them will be mentioned in the following "Reference Manual". Nevertheless, it seems reasonable to repeat them in a more concentrated form here, although this happens to make this chapter a real topsyturvydom... a) The ERROR-concept: if an error occurs in one of ANIVGA's routines, the global variable ERROR will be set accordingly. This gives you the freedom either to check this variable each time you called a routine - or ignore it for improved speed. As a rule of thumb, you should always check this variable while your program is still in the testing phase - and "comment out" these sections when you are through with debugging. (Conditional defines are great for that job!) Note that there are some routines that do not set ERROR at all (like Screen, GetPixel, PageGetPixel, PagePutPixel), either because in some special cases, "nice" tricks can be played with "faulty" parameters or because of severe speed improvements! For example, if you are going to read a 5000 pixel area from the screen with PageGetPixel(), it would be crazy to check 5000 times whether the "page" given to read from is valid or not. b) Pixel-drawing routines: basically spoken, there are three sorts of graphic data objects in ANIVGA: sprites, pixels and background images. Because of ANIVGA's working scheme, all routines handling pixels (PutPixel, PagePutPixel, Line, PutImage,...) must be used in a special form: - If you use them to "draw" into the background page, this can only be done when using background mode STATIC (because in mode SCROLLING, the back- ground is stored in a compressed format one can't access directly). - Drawing into the background page in mode STATIC is fine (that's the main advantage of this mode compared with mode SCROLLING), and the best time to do it is _before_ calling Animate(), because changes to the background image will then be visible with the call to this routine. - Drawing "on the monitor screen" will be visible exactly for one animation cycle, that is: until the next call to Animate(). For this reason, you must do this changes _after_ calling Animate() and at the _visible_ page 1-PAGE (not the _actual_ page PAGE itself). It is not that difficult as it may sound at first glance; for example: ... REPEAT read_user_inputs; compute_necessary_actions; do_all_changes_to_the_background_image; do_all_changes_to_the_sprites; Animate(); do_all_changes_to_the_visible_screen; {e.g.: Line(0,0,XMAX,YMAX,1-PAGE)} UNTIL user_wants_to_end_application ... This way, after having called Animate(), the changes to the background (and your sprites) will be visible (because Animate() has generated an appropriate picture) and your changes to this image with the pixel- drawing routines will be visible "at once". That image will then stay visible until the next call to Animate(). (Simply spoken, you let Animate() generate and display a picture and then do some changes to the picture while it is diplayed) - Because of unavoidable memory restrictions, ANIVGA can't store pixels drawn offscreen: if ANIVGA sees that points/lines lie outside the visible screen, it just does nothing at all; in other words, you can't draw a line outside the screen and "scroll it in" five minutes later! (You would have to define the line as a sprite instead, because sprites are the only objects stored independently). c) Coordinates: Throughout all routines, ANIVGA works with _virtual_ coordi- nates (that is, values in the range xε[-16000..+16000], yε[-16000..+16000]), but sometimes you will have to address _absolute_ coordinates (in the range xε[0..XMAX], yε[0..YMAX]), so you have to transform virtual coordinates into absolute coordinates (or vice versa), which is _very_ easy: virtual coordinates -> absolute coordinates: Xabsolute := Xvirtual - StartVirtualX Yabsolute := Yvirtual - StartVirtualY absolute coordinates -> virtual coordinates: Xvirtual := Xabsolute + StartVirtualX Yvirtual := Yabsolute + StartVirtualY d) Background / valid pages: Many routines expect a graphic page number as parameter. As mentioned under b), BACKGNDPAGE is valid only when you use background mode STATIC. Nevertheless, you can draw to this page even when you are using background mode SCROLLING without getting an error "Err_InvalidPageNumber" (although you are _strongly_ discouraged to do so)! That's because you can play some tricks on ANIVGA this way, provided that you do know _exactly_ what you (and ANIVGA) are doing, but this "feature" will probably be cut off in future versions of this program. (Note that this doesn't mean that you can't switch between STATIC and SCROLLING backgrounds during runtime! - It only says that you can't use the two background pages _in parallel_ (=at the same time)!) e) Display objects at the same abolute screen position: Let us assume you want to display a score at the upper right corner of the screen; that's not hard when using STATIC background: just define your score as a sprite and choose an appropriate coordinate pair. In SCROLLING mode, your score would scroll away, too, so you must tie it to absolute screen coordinates, as said in c), but there is a simple rule which can be derived from the equation absolute_coordinate := virtual_coordinate - StartVirtual_value To ensure that the absolute (=screen) coordinate stays the same, you have to balance out changes done to the StartVirtual-variables like this: whenever you increase/decrease StartVirtual? by some amount delta, increase/decrease your score-coordinates by the same amount delta! (This results in: new_coord := virtual_coord±delta - (StartVirtual±delta) = virtual_coord - StartVirtual = old_coord as wanted) f) Displaying scores: another way to display a score without defining it as a sprite would be to simply draw it to the screen with the pixeldrawing rou- tines or OutTextXY(): ■ draw it to the visible page (1-PAGE) each time after having called ANIMATE() ■ draw it to the background page BACKGNDPAGE The last method is applicable only in background mode STATIC and you have to restore the background image in the used area manually, but has the ad- vantage that you must redraw your score only when it really changed (instead of every animation cycle as with the first method). One way to accomplish that would be to use the GetImage() and PutImage() routines: ... build background image; use GetImage() to get a copy of the background area which will be overdrawn by the score; ... main_loop: IF new score has to be displayed THEN BEGIN use PutImage() to restore old background area underneath the score; use OutTextXY() to write new score into the background image END ... g) Speed: It is hard to predict the speed of animations, because that is merely determined by the speed of your VGA card, not your computer's CPU clock rate! E.g., a program runs faster on my old AT (8MHz) than on a fast (25 MHz) 80386 machine - only because of a better VGA card installed in the AT! Stated otherwise, if you use a computer with "enough" CPU-power, you won't have to think much about "should I use STATIC background instead of SCROL- LING for improved speed?", because it won't matter anyway! The break even point, where the VGA-card's bottle neck becomes the limiting factor depends largely on your application (and your VGA-card, of course), but as a rule of thumb, clock speeds faster than 12MHz won't improve your program speeds *linearly* any further: animation ^ ______ speed │ ___---- │ / │ / │/ ┼─────┬───────────> clock rate break- even point Note that your programs will still profit from faster CPU's, but that is due to faster computation of all routines not limited by accessing the video RAM; even on the fastest clones, the IBM-bus-clock-rate is not faster than 10MHz -- and this limits accessing the VGA card: sad, but true... g) DMA access: Quite a long time, I tried to speed up animation rates by using the DMA-chip in parallel to the CPU: while the CPU is running your program, the DMA should move around memory. Unfortunately, I had to find out that most computers don't like DMA memory- to-memory transfers at all and those who do don't work when addresses used reference the video RAM area (I can't explain why this is the case). If someone out there has successfully worked with the DMA chip this way, I would be glad to know! 7. Credits ────────── Honour to whom honour is due! Although most of the routines are mine, two of the utility programs (also written in TP6.0) use stuff from other Freeware authors: - The GRAB-utility uses Ken Pottebaum's TSR-unit TSRUNIT.ZIP and - The MAKES-designer uses John Bridges' BGI-driver SVGA256.BGI (for the VGA's 320x200x256 mode $13) from his SuperVGA-driver package SVGABGI3.ZIP (Both programs are available at the SIMTEL20-servers) Thanks to them for supporting the Freeware-concept, their spirit made it possible to distribute this program as Freeware, too! 8. ANIVGA Reference Manual ────────────────────────── This reference manual lists all routines, variables, constants and a lot of in- formational stuff concerning ANIVGA in alphabetic order. Don't get frightened about the amount of informations given; in normal appli- cations you will need only a few of them! ABSOLUTE COORDINATES - information ────────────────────────────────── See : coordinates Animate - procedure ─────────────────── Function : Performs a complete animation cycle Declaration: {$F+} PROCEDURE Animate {$F-} Description: A call to Animate() clears the invisible graphic page by copying the contents of the background image into the actual drawing page (specified by variable PAGE). Then all active sprites (SpriteN[i]<>0) in the visible window (determined by StartVirtualX and StartVirtualY) are drawn in the style and at the coordinates given by the user. After that, the routine waits for a vertical retrace to reprogram the VGA adapter to flip the display pages, making the completed image visible and changes PAGE to point to the new, invisible graphic page. Finally, the procedure looks how much time passed since the last animation cycle and if this time is less than that set by SetCycleTime(), the program waits accordingly. Note : This procedure is the kernel routine which has to be called every- time when you have set all data for a new animation frame. See also : PAGE, SetCycleTime, StartVirtualX, StartVirtualY BackGndPage - constant ────────────────────── Function : Holds the page number of the backround page Declaration: CONST BACKGNDPAGE=2; Description: When using background mode STATIC, BackGndPage specifies the page number of the background image for the animations to be used. Note (!) : Use of this constant only makes sense when using background mode STATIC! See also : ScrollPage, Background Background - information ──────────────────────── The term "background" specifies a graphic image in front of which all anima- tions take place. There are two sorts of background in ANIVGA: SCROLLING background and STATIC background, which you choose with SetBackgroundMode(). As its name states, a STATIC background cannot be scrolled: it consists of a 320x200 pixels picture. This background picture is stored in the graphic page numbered BACKGNDPAGE. At the very start of every animation cycle, the routine Animate copies that picture into the actual drawing page, thus erasing old stuff on that page and building the basis for the new image. As a normal bitmap picture, it is 320x200=64000 bytes in size. If you use the GRAB-Utility or the WritePage()-Routine to save an image, a three byte header is put ahead of the information, thus extending the size to 64003 bytes. The second background sort is called SCROLLING: like ANIVGA's virtual coor- dinates, you can define a huge background image and scroll over it. Unfortunately, it is impossible to hold a complete background picture in memory: you would need 32000*32000=1024000000 bytes RAM (!) to do that. Instead, ANIVGA uses a "tiling" mechanism: tiles are small pictures (16x16 pixels) which can be combined freely to build the background image. You can use up to 256 different tiles and "pin" them on an background area of up to MaxTiles (=10000) tiles; everything outside of this background area will be assigned to tile no. 0 automatically. For example, let us assume that you use only scrolling in the y-coordinate axis, 16 screens in total: thus, your x-coordinates reach from 0 to 319 and your y-coordinates from 0..(16*200-1)=5119, which gives an area of 320*5120 =1638400 pixels. This is equivalent to (320/16)*(5120/16)=20*320=6400 tiles (remember: each tile consists of 16x16 pixels!). So you would define the scroll range for the background area needed with SetBackgroundScrollRange(0,0,319,5119) and start "painting" your background: You could design up to 256 different tiles and use them to assemble your background image (=those 6400 tiles). Most often, only a few are needed, because the background image isn't that dramatically different all over the place. For simplicity, let's assume that you need only 20 different tiles, numbered 0..19 respectively in the following order to build your background image: (0,0) (319,0) ┌────────┬────────┬────────┐ ┌────────┬────────┬────────┐ │ │ │ │ │ │ │ │ │ 0 │ 1 │ 2 │ ... │ 13 │ 14 │ 15 │ │ │ │ │ │ │ │ │ ├────────┼────────┼────────┤ ├────────┼────────┼────────┤ . . . . . . . . . . . . . . . . . . ├────────┼────────┼────────┤ ├────────┼────────┼────────┤ │ │ │ │ │ │ │ │ │ 0 │ 1 │ 2 │ ... │ 13 │ 14 │ 15 │ │ │ │ │ │ │ │ │ └────────┴────────┴────────┘ └────────┴────────┴────────┘ (0,5119) (319,5119) Now all you have to do is to tell ANIVGA that layout with the PutTile command: {assuming SetBackgroundScrollRange(0,0,319,5119) has been set} number:=0; y:=0; {better: y:=BackY1} REPEAT (things would become easier if Pascal would know a STEP-command...) x:=0; {better: x:=BackX1} REPEAT PutTile(x,y,number); number:=(number+1) MOD 16; inc(x,16); UNTIL x>319; {better: x>BackX2} inc(y,16); UNTIL y>5119; {better: y>BackY2} That's it! (It is better to use the (global defined) "Back..."-variables, set by the former SetBackgroundScrollRange()-call, because ANIVGA has to adjust values on multiples of 16, see SetBackgroundScrollRange()/Back?? for more details). So then, why should one use STATIC backgrounds after all when there is such a powerful instrument like SCROLLING backgrounds? There are two simple answers: speed and simplicity! - First, SCROLLING back- grounds take a lot of work to compute, which slows down animations (unless you have a fast machine, because then the VGA's memory access time becomes the limiting factor). Second, it is easy to do some "tricks" on static backgrounds: draw a line in the static background page and >zap!< starting with the next animation cycle, it will be visible for all times. Stated otherwise, when using scrolling background, you cannot use drawings to the background image, because it simply doesn't exist explicitly, you are restricted solely to "tiles" and "sprites"! (On the other hand, you can play nice tricks on scrolling background by changing single tiles...) So consider carefully what mode you are going to use for your application! See also : BACKGNDPAGE, BACKGNDADR, WritePage, LoadPage, WriteBackgroundPage, LoadBackgroundPage, SetBackgroundMode, LoadTile, Tile BackgroundGetPixel - function ───────────────────────────── Function : Reads a background pixel's color Declaration: {$F+} FUNCTION BackgroundGetPixel(x,y:INTEGER):BYTE; {$F-} Description: This routine will return the color value of the specified point with virtual coordinates (x,y) in the background image. If the corresponding absolute coordinates lie outside the screen, zero (= black) will be returned. Note : Use of this routine works only when using background mode STATIC! It might look strange to use virtual coordinates then, although the background is said to be static (= non-scrollable) and hence restricted to absolute coordinates anyway, but it is often con- venient to use an uniform notation and it is easy to convert co- ordinates accordingly (see "coordinates" for more about that). See also : coordinates, GetPixel, PageGetPixel BackgroundLine - procedure ────────────────────────── Function : Draws a line on the background page Declaration: {$F+} PROCEDURE BackgroundLine(x1,y1,x2,y2:INTEGER); {$F-} Description: To draw a line on the background page (thus alterating the back- ground), you can use this procedure. Like the similiar Line()- routine, it uses virtual coordinates, too. If necessary, the line will be clipped down to its visible part (using a special Sutherland-Cohen algorithm). Note : Use of this routine only makes sense when using background mode STATIC! See also : Line, coordinates BackGroundMode - variable ───────────────────────── Function : Holds the actual choosen background mode Declaration: VAR BackgroundMode:BYTE; Description: Using SetBackgroundMode(), you can select one of the possible background modes STATIC or SCROLLING. BackGroundMode stores this value. Note (!) : Only read this value, never change it directly! See also : Background, SetBackgroundMode BackgroundOutTextXY - procedure ─────────────────────────────── Function : Writes a textstring to the background page BACKGNDPAGE Declaration: {$F+} PROCEDURE BackgroundOutTextXY(x,y:INTEGER; s:STRING); {$F-} Description: This routine is exactly the same like OutTextXY() (see there), but it writes the string into the background page (so it will be visi- ble permanently). Note : Use of the routine only makes sense if STATIC is used as background mode. See also : GraphtextColor, GraphtextOrientation, GraphtextBackground, OutTextXY, background BackgroundPutPixel - procedure ────────────────────────────── Function : Plots a point into the background page Declaration: {$F+} PROCEDURE BackgroundPutPixel(x,y:INTEGER; color:BYTE); {$F-} Description: (x,y) specify the virtual coordinates of the point to be drawn in color "color". If this point lies onscreen (i.e.: its _absolute_ coordinates are between (0,0)..(319,199)), it will be drawn on the background page BACKGNDPAGE (and become visible starting with the next animation cycle). Note (!) : - Use of this routine makes sense only when using background mode STATIC! - This routine works with virtual coordinates! - Although this seems silly at first glance (because in STATIC mode, background coordinates are always restricted to (0,0)..(319,199)), it appears to be handy in many situations. If you actually want to address points absolute coordinates (a,b), you can call this routine with coordinates (a+StartVirtualX,b+StartVirtualY) instead. - Because of ANIVGA's working scheme, you probably want to call this routine _before_ calling Animate(), so that changes of the point will be visible as soon as possible. See also : PutPixel, PagePutPixel, background, coordinates, How ANIVGA works BACKX1, BACKX2, BACKY1, BACKY2 - variables ────────────────────────────────────────── Function : Hold the background image boundaries in background mode SCROLLING Declaration: BackX1,BackY1,BackX2,BackY2:INTEGER; Description: When background mode SCROLLING is to be used, you have to define a scrolling area (with SetBackgroundScrollRange()). Due to inter- nal management restrictions of ANIVGA, the boundaries of this area must fall on coordinates which are multiples of 16 ("on a grid with mesh 16"). If the values you supply don't fulfill this restriction, ANIVGA adjusts them automatically to do so and stores them to these variables for further use. Note : The only reason these variables are visible to you are that it could be necessary for you to notice adjustments ANIVGA did; so: only read this values, never change them directly! (Look at "background" for an example). See also : background CloseRoutines - procedure ───────────────────────── Function : Terminates ANIVGA Declaration: {$F+} PROCEDURE CloseRoutines; {$F-} Description: Calling this routine switches back from ANIVGA's special graphic mode into the graphic or text mode previously set. Note : This should always be the last call to a routine of ANIVGA in your programs. See also : InitGraph COLLISION-DETECTION, CONCAVE, CONVEX - information ────────────────────────────────────────────────── A graphical figure can be classified by its outline into one of two groups, called "concave" or "convex" figures. To motivate this mathematical notion >eh, don't get frustrated...<, regard your sprite only given by its "outmost" points, which connected together shape the figures boundaries. The figure is called "convex" :<=> every pair of arbitrarily choosen points on this boundary build a line which is totally inside (or at least on the boundary of) the figure: ┌──────┐ This rectangle is "convex", because whenever you choose two points │ │ on its boundaries and connect them, the resulting line lies com- └──────┘ pletely inside (or on the boundary) of the rectangle itself. ┌──────┐ On the other hand, this figure would be "concave", because if you └─┐ ┌─┘ choose the top-right and bottom-right corner (say) and connect them, ┌─┘ └─┐ then the middle part of the resulting vertical line lies outside the └──────┘ figure. That is (in a very lax form) the _mathematical_ definition of these terms, but ANIVGA completely deals with either horizontal or vertical lines, so that an extension of these terms can be made: A sprite is called "horizontal concave" ("vertical concave"), if a horizontal (vertical) line connecting two points of the sprite's boundary can be found so that parts of this line lies outside the sprite; if the sprite is not hori- zontal (vertical concave), it is "horizontal convex" ("vertical convex"). In that sense, the second of the figures above is "vertical concave", but "horizontal convex"! (Notice that figures which are concave in the pure _mathematical_ sense are sometimes treated as convex by this definition, as this cross:) ┌─┐ (If you use either a horizontal or vertical "scan line" sweeping ┌─┘ └─┐ throughout the cross, there will be never more than one part of └─┐ ┌─┘ the "scan line" which belongs to the figure; you can use this └─┘ principle as a second definition for horizontal/vertical convex) This terminology comes in handy when describing some mechanisms of ANIVGA: a sprite is drawn LINEwise. For this, every point between the leftmost and right- most point of a sprite's line is considered to be an _inner_ point of the sprite, thus ANIVGA assumes a horizontal convexity! If your sprite isn't, like this one... ┌─────┐ ...and the points between the two "legs" of this sprite shall still │ ┌─┐ │ be treated as "transparent" (assuming they have been defined with │ │ │ │ color "black" (=0)), you must use display mode "Display_NORMAL", │ │ │ │ because the "Display_FAST" mode would treat them as belonging to the └─┘ └─┘ sprite itself and draw them as "covering" black. (To state it otherwise: whenever your sprite is (at least) horizontal convex and you don't need the feature of transparent parts inside the sprite, you can use the "Display_FAST" mode without any loss of accuracy in the sprite display) Tip: the spritemaker program MAKES allows to display a sprite's horizontal boundaries, which makes it easier for the beginner to decide about that figure's convexity. But whenever you are unsure, you still can use mode "Display_NORMAL" for drawing it. --- Things get a bit more tough when deciding if two sprites collide or not (which is an important task): in difference to many sprite toolkits, ANIVGA doesn't use a "mask" approach, which makes sprites big and collision detection slow. Instead, ANIVGA uses a sprite's outline to decide whether two sprites collide. For that, it computes for every line (column) of the overlap region of the sprites' surrounding rectangles, whether the sprites overlap horizontally (vertically) and says "collision!" only if there are intersections in both directions. In pseudo code: IF smallest_box_around(sprite1) doesn't intersect smallest_box_around(sprite2) THEN no_collision ELSE BEGIN compute the lines and columns for which the 2 sprite rectangles overlap FOR every such line compare -with the help of the sprite boundaries- if the corresponding lines overlap FOR every such column do the same check ONLY_IF there is an intersection in at least one line AND one column THEN collision! ELSE no_collision END If you think a byte (=8 bits...) about this algorithm, you'll see that it can lead to misdetection, in that the algorithm says "collision!", although there is none (but it still guarantees that if there _is_ a collision, the alg. will detect it) as in the following example: ┌─────┐ └───┐ │ ┌────────┐ │ │ │ ┌────┐ │ │ │ │ │ ┌─┐│ │ │ │ <─ In this line there is a "horizontal collision" (that is, └─┘ │ │└─┘ │ │ the two sprites overlap in their horizontal dimension) │ └────┘ │ └────────┘ ┌─ In this column there is a "vertical collision" ^───────┘ To state things without a proof here, such an (unavoidable) misdetection is only possible, if at least one of the two sprites is neither horizontal nor vertical convex!!! Even then, it takes special constellations (as the one above) to produce such an error, so that in praxis, it is very unlikely for such an error to occur. Color - variable ──────────────── Function : Determines the actual drawing color Declaration: VAR Color:BYTE; Description: Various drawing routines use this global variable to determine which color should be used. Note : ANIVGA uses the standard color table of the 256-color mode $13. See also : - ColorTable - type ───────────────── Function : Supply a data type for self-defined "Shadow Tables" Declaration: TYPE ColorTable=ARRAY[0..255] OF BYTE; Description: If you want to use a different color look-up-table for your sprites in display mode Display_SHADOW than can be achieved with SetShadowTab(), you must build a table like this. Each entry gives the color which should be used to replace the original color with that index, i.e.: if c is of type ColorTable and c[5]=9, this means that every point of your sprite which is to be drawn over a pixel with color 5 should replace that pixel with color 9. You can find an example how to activate such a "home-brew" table at "ShadowTab". Note : - See also : ShadowTab, SetShadowTab, Display modes COORDINATES - information ───────────────────────── ANIVGA has to deal with two kinds of coordinates: "virtual" and "absolute" ones. An absolute coordinate lies in the range 0..319, 0..199 for the x and y values, respectively. It names a unique point on your graphic screen. However, ANIVGA doesn't restrict animations to take place on the visible graphic screen: its routines deal with coordinates in the range -16000..+16000 in each direction, called "virtual coordinates". The picture you view while ANIVGA's routines are running is a window of that virtual screen, 320 points wide and 200 points high. Naturally, the graphic hardware only knows absolute coordinates and thus, ANIVGA has to transform virtual in absolute coordinates. It does this with the help of the two variables StartVirtualX and StartVirtualY which together speci- fy the starting point of the upper left corner of your actual screen window; e.g. if (StartVirtualX,StartVirtualY) was (1000,2000) then you would look at the part of ANIVGA's world which consists of the 320x200 region with the coor- dinates xε(1000..1319) and yε(2000..2199). Note that there is one severe restriction, though: because it is absolutely impossible to hold a complete "virtual" screen bitmap for ANIVGA's world in memory (it would need app. 1GB RAM!), all drawing commands only take place on the visible screen. This means that you can't draw lines, points or any other objects which are _not_ sprites outside the visible window that become visible, when you scroll your window over to that part of the virtual screen. For example, if you draw a point somewhere outside your visible window (say at (-10000,1234) while your visible window starts at (500,900)) and pan to that region afterwards (by set- ting (StartVirtualX,StartVirtualY)=(-10100,1200) or something like that), you won't see that point: it is stored nowhere. (The only way to circumvent this is to define the point as a sprite and set its coordinates (SpriteX[],SpriteY[]) to (-10000,1234), because sprites are the only objects which the system stores!). More general: Because there is _no_ complete virtual screen, all information drawn outside the coordinate range visible at the moment will be lost and all information read in from these "offscreen" pixel positions will be zero (= black). For that reason it may seem strange for some routines that were restricted in their use to the "real" (= absolute coordinate) screen region to use virtual coordinates inspite (e.g.: GetImage, BackGroundGetPixel,...), but this was done intentionally, because it leaves room for further improvements: if it should be possible some day to store a complete virtual screen image, there will be no changes necessary in ANIVGA's syntax. Meanwhile, it is simple to transform absolute and virtual coordinates into each other whenever necessary, using the following equivalence: virtual X-coordinates - StartVirtualX = absolute X-coordinates virtual Y-coordinates - StartVirtualY = absolute Y-coordinates As a result: virtual coordinates lie in the range -16000..+16000, the start of the visible part is defined in StartVirtualX and StartVirtualY and only sprites can be "scrolled in" into the visible screen, while all other objects are "lost". Display modes - information ─────────────────────────── ANIVGA is able to display a sprite in several "modes". This describes how the sprite's data should be handled when drawing the sprite to the screen. Up to now, there are three modes: - Display_NORMAL - Display_FAST - Display_SHADOW This mode is linked to a sprite's physical data by creation of the sprite with the spritemaker program (and defaults to Display_NORMAL), but can be altered once the sprite is loaded into memory with the procedure SetModeByte(). Note that the display mode information is part of the _physical_ sprites (that is, the memory image of the bytes loaded at the beginning), not the _logical_ sprites (the "handles" in the SpriteN-array to this physical data). For that reason, a change of the display mode of a sprite with spriteLOAD number 123 (say) will affect _all_ sprites of type 123 (= all entries in SpriteN[] with value 123). This is intended, because the display mode is a piece of informa- tion reflecting the sprite's physical structure. In mode "Display_NORMAL" you can think of a sprite as a picture with holes at the places where its pixels have color 0: when displayed, all the parts of the sprite with color<>0 will cover (paint over) the screens original pixels, but the pieces with color=0 will act like "window panes": the original contents of the screen remain visible there. This mode is useful for all kinds of sprites which have such opaque holes in- side themselves: cars/planes/houses or other objects with window panes, but also all "concave" sprites. Note that black, covering parts must be realized with a dark color<>0, for example color 16. "Display_FAST" is a bit (but not that dramtically) faster than the last method, because it doesn't know of a special color: all sprite data is treated equally and stored to the screen at once. For that, all parts of the sprite are covering. (But note that a sprite consists only of the points inside and on its boundaries: all the points of the smallest box surrounding it -that is the way a sprite is stored- doesn't matter). You will use this mode whenever you have sprites which meet the following re- quirements: they are "convex" and don't have any transparent parts inside them- selves. "Display_SHADOW" is a tribute to the fact that one often needs some kind of shadowing to give the impression of an freefloating object or other pseudo 3D-effects. In this mode, the sprite's real colors are insignificant, only its boundaries and the actual contents of the screen where the sprite shall be drawn are important. The color of every sprite point is determined by the color of the appropriate screen point. The color of these points are translated by the lookup table ShadowTab into darker ones. If you want to give a sprite a shadow zone, then you must divide your sprite into two ones: one building the sprite itself and a second one to realize only that shadow area, and compose them with appropriate coordinates. Technically spoken, there are short code areas in ANIVGA's routines reserved in which the right piece of code to transfer/interpret the sprite's data become copied, when not already there. For optimal performance it is wise to group the entries in SpriteN[] such that adjacent sprite entries share the same display method. See also : convex, concave DUMP_SPR - utility ────────────────── (This is surely a tool for all those hackers among us...) If you want to take a closer look at a sprite's data, you don't have to fiddle around with DEBUG or the like, just use this sprite dumper: it takes a (binary) sprite file (*.COD or *.LIB) and disassembles it into readable ASCII-text. You can redirect the output to a file or printer, e.g.: DUMP_SPR mysprite.cod >mysprite.txt would dump the sprite file "mysprite.cod" to the ASCII-text file "mysprite.txt" for further usage. Note that DUMP_SPR creates a format which will be understood by assemblers like MASM or TASM so that you can reassemble the files to get a binary sprite file once again! ERROR - variable ──────────────── Function : Holds the code of the last error which occured Declaration: VAR ERROR:BYTE Description: If an error occurs while executing one of its routines, ANIVGA terminates that routine and sets ERROR accordingly to reflect that error. You can use GetErrorMessage() anytime to get more information, which error occured. It is your responsibility to check if such an error occured and react in an appropriate way. For the possible values and their descriptions returned by GetErrorMessage, see there. Note (!) : - After processing an error, you have to reset the variable back to Err_None yourself" - In respect of future extensions, you should treat every value <> Err_None as an error - The most frequented routine Animate() doesn't produce any errors, neither do several other procedures. As a basic rule, all routines which have to do with file I/O have to be checked. - ERROR is initialized with Err_None See also : GetErrorMessage, InitRoutines FillBackground - procedure ────────────────────────── Function : Fills the background page with the specified color. Declaration: {$F+} PROCEDURE FillBackground(color:BYTE); {$F-} Description: The given value is written into the whole graphic page BACKGNDPAGE and thus defines the picture before all animations take place to have one color. Note : Use of this routine only makes sense when using background mode STATIC! See also : Background, BACKGNDPAGE, BACKGNDADR, GetBackgroundFromPage, LoadBackgroundPage FillPage - procedure ──────────────────── Function : Fills a graphic page completely with a given color Declaration: {$F+} PROCEDURE FillPage(pa,color:Byte); {$F-} Description: If you want to paint a complete page uniformly with one color, then this will be the fastest method to do it: specify the graphic page (0,1 or BACKGNDPAGE (=2)) in "pa" and the color to be used in "color". Note : - Although possible, you are strongly discouraged to use this pro- cedure in background mode SCROLLING (i.e.: pa=SCROLLPAGE (=3) as page number), because the background is treated completely dif- ferent! - Remember also that changes to one of the drawing pages (0 or 1) have to be applied _after_ calling Animate and will be visible for exactly one animation cycle, whereas changes to the back- ground page remain permanent (and are best done _before_ calling Animate, although that's not peremptory). - This routine is great to produce "flashing" screens: apply it to 1-PAGE (the visible page). - Possible ERROR-values returned are Err_InvalidPageNumber See also : background, How ANIVGA works, LoadPage, LoadBackgroundPage, GetBackgroundFromPage FontOrient, FontHeight, FontWidth - type/constants ────────────────────────────────────────────────── Function : Supply some additional data about the internal font Declaration: TYPE FontOrient=(horizontal,vertical); CONST FontHeight=6; FontWidth=6; Description: The internal font used for displaying graphic text (OutTextXY(), BackgroundOutTextXY()) can be displayed either horizontally or vertically; use of the TYPE FontOrient simplifies that. To compute the width/height of a text, the constants FontHeight and FontWidth can be used, which specify the size of one letter. Note : - See also : OutTextXY, BackgroundOutTextXY GetBackgroundFromPage - procedure ───────────────────────────────── Function : Take over one of the drawing pages as background image Declaration: {$F+} PROCEDURE GetBackgroundFromPage(pa:Byte); {$F-} Description: Specify the graphic page (0 or 1) from which the image should be "captured" and the routine will copy its contents into the back- ground page BACKGNDPAGE (=2) as new background image. Note : - Use of the routine only makes sense if STATIC is used as background mode. - Possible ERROR-values returned are Err_InvalidPageNumber See also : LoadBackgroundPage GetErrorMessage - function ────────────────────────── Function : Returns a description of the last error occured Declaration: {$F+} FUNCTION GetErrorMessage:STRING; {$F-} Description: Although you can use the ERROR variable directly to evaluate any error and inform the user about it, it is often more comfortable to let ANIVGA do that: GetErrorMessage will give you a string describing the last error which occured in words. The possible string contents and the corresponding ERROR values are: Err_None: 'No Error' No error occured during the routine; this is the variable's initial value Err_NotEnoughMemory: 'Not enough memory available on heap' The program couldn't load sprites or other data to the heap Err_FileIO: 'I/O-error with file' There was an error reading the file; either the file doesn't exist at the path given or it is damaged Err_InvalidSpriteNumber: 'Invalid sprite number used' This error occurs if you try to load a sprite with a sprite loadnumber not in the valid range 1..LoadMAX Err_NoSprite: 'No (or corrupted) sprite file' While attempting to interpret the data just read in, ANIVGA found the data not to be in the expected format; either because you used a wrong data file or it is damaged Err_InvalidPageNumber: 'Invalid page number used' There are four graphic pages, numbered 0..3. Page 0 & 1 are used for the animation itself, page 2 ("BACKGNDPAGE") holds the static background image and page 3 ("SCROLLPAGE") is reserved for the scrollable background information Err_NoVGA: 'No VGA-card found' The animation package needs a VGA (or compatible) graphic card but couldn't find one Err_NoPicture: 'No (or corrupted) picture file' The background picture file ANIVGA should load has not the ex- pected size/format or a DOS-error occured while attempting to access the data Err_InvalidPercentage: 'Percentage value must be 0..100' If you set the colortable for the shadowing effects of sprite display mode Display_SHADOW, you must use a percentage value giving the remaining brightness of the colors in the shadow areas, which must be in the range 0..100%, of course Err_NoTile: 'No (or corrupted) tile/sprite file' There was an error loading the specified sprite file(s) and interpreting them as background tiles. Most often this occurs because the sprite doesn't meet the requirement to be a multiple of 16 points in its x- and y-directions! Err_InvalidTileNumber: 'Invalid tile number used' There may be only 256 background tiles, numbered 0..255 Err_InvalidCoordinates: 'Invalid coordinates used' The virtual background coordinates you use must lie in the range (BackX1,BackY1)..(BackX2,BackY2), which has been specified with SetBackgroundScrollRange() Err_BackgroundToBig: 'Background too big for tile-buffer' ANIVGA's tile buffer can hold no more than MaxTiles (=10000) tiles, that is an area of 10000*16*16 pixels². Check the area you specified in your SetBackgroundScrollRange()-call! Err_InvalidMode: 'Only STATIC or SCROLLING allowed here' The only background modes ANIVGA knows are STATIC and SCROLLING Err_InvalidSpriteLoadNumber: 'Invalid spriteload number used' spriteLOADNumbers must lie in the range 0..LoadMAX; when you get this error, you probably confounded a spriteLOADnumber with a spritenumber (else): 'Unknown error' If ERROR has none of the above values, this string will be returned; this should never happen, though. Note : Calling GetErrorMessage won't set back the ERROR variable either; you must do that explicitly! See also : ERROR GetImage - function ─────────────────── Function : Makes a copy of the specified screen region Declaration: {$F+} FUNCTION GetImage(x1,y1,x2,y2:INTEGER;pa:BYTE):POINTER; {$F-} Description: - This function works much the same as its equivalent in Turbo- Pascal: (x1,y1) and (x2,y2) define the upper left and lower right corners of the screen part to save, but now these coordinates are _virtual coordinates_, the routine reserves the memory needed to hold the copy itself and you can specify the graphic page, from which the image is to be taken (pa=0,1 or BACKGNDPAGE (=2) ). - As result you get a pointer to the start of the saved image, which can be used with PutImage(). - If there is not enough memory available or the specified part of the screen lies completely outside the visible screen, NIL is returned. - Besides that, there are 5 global variables which are set accor- dingly: was_cut:BOOLEAN = TRUE/FALSE, if the image had to be _partially_ clipped (if the specified image is totally offscreen, was_cut stays at FALSE!) left_cut, right_cut, top_cut, bottom_cut:WORD hold the size how much had to be clipped off at the boundaries; these values are only set when was_cut=TRUE (If you wonder about this odd definitions: GetImage was intended to work only with the visible screen (that is: with _absolute_ coordinates): together with its counterpart PutImage(), you can copy a part of the screen to another part or page. In that case, you do not have to fiddle around with clipping: just issue a GetImage() and use PutImage() to paste this block elsewhere. But there may be some applications, when you cut out part of the screen and think you got the complete graphic figure you wanted, although (because of the use of virtual coordinates and your figure being partially offscreen) you got only part of it. Checking "was_cut" informs you about such a partial clipping. If your figure is completely offscreen, that is a special case: it depends on your application whether this should be treated as being okay or not; if you need special treatment (as with partial clipping), you still can check for this with something like: ... image_ptr:=GetImage(x1,y1,x2,y2,1-PAGE); {1-PAGE=visible page!} IF ERROR<>Err_None THEN ... {probably not enough memory} ELSE IF (was_cut) OR (image_ptr=NIL) THEN ... {partial or total clipping occured} ELSE ... {no clipping at all} ) - possible ERROR-values returned are: Err_NotEnoughMemory and Err_InvalidPageNumber Note : As already mentioned, GetImage() only works on screen regions in the _absolute_ coordinate range 0..319, 0..199, but expects _virtual_ coordinates! See also : PutImage, coordinates GetModeByte - function ────────────────────── Function : Returns the actual display method set for a sprite Declaration: {$F+} FUNCTION GetModeByte(Sp:WORD):BYTE; {$F-} Description: "Sp" specifies the spriteLOADnumber of the sprite from which the user wants to know the display mode. The function will return one of the valid modes Display_NORMAL, Display_FAST or Display_SHADOW. Note : - Again, spriteLOADnumbers are used! - If the LOADnumber given doesn't exist (because no sprite has been loaded with that number), the routine will return Display_UNKNOWN instead. See also : Display modes, SetModeByte GetPixel - function ─────────────────── Function : Reads a pixel's color Declaration: {$F+} FUNCTION GetPixel(x,y:INTEGER):BYTE; {$F-} Description: Returns the color value of the specified pixel with the virtual coordinates (x,y) on graphic page PAGE. If (x,y) lies offscreen (to be precise: the computed absolute coordinates lie offscreen), then zero (= black) is returned. Note : Be aware that PAGE is the invisible page, not the one you are looking at! See also : coordinates, PAGE, PageGetPixel, PutPixel GRAB - utility ────────────── GRAB allows you to "steal" graphics from other applications and convert them into sprite files (*.COD) or background images (*.PIC) for use with ANIVGA. This program is a terminate-and-stay-resident (TSR) utility that has to be run before starting those applications from which you want to capture graphic images. Pressing the hotkey CTRL-ALT-G will popup a frame which you can move and resize to select the part of the graphic sreen you want to save (if you are not in a graphic mode, a graphic mode unknown to GRAB or in a "MSDos critical" situation you'll here a beep instead). Use the "i/j/k/m", arrow and "8/6/2/4" keys for that task. The space bar will toggle between which corner (the upper left or lower right one) will be used for resizing the box. Press ESC anytime to escape from GRAB back to your application. By default, GRAB starts in sprite capture mode: if you press "s"ave, "w"rite or just RETURN, GRAB will generate a sprite file (starting with the file name GRAB_000.COD and counting up for following sprites). To get a background image, toggle into screen capture mode by pressing "t" (a second "t" will switch back to sprite capture mode again), select the screen region wanted and press "s", "w" or RETURN to get that part of the screen in the file GRAB_000.PIC (or what- ever number is actual then). Naturally, you can't resize your frame in the screen capture mode: it stays at its initial size of 320x200 points. Note that GRAB doesn't save color palettes, but only the actual color values of all the pixels selected. Because ANIVGA uses the standard palette of graphic mode $13, it is possible that images captured with GRAB may have different col- ors when used in MAKES or ANIVGA, whenever the application from which you cap- tured changed the standard palette! Note also that there is the same restriction for a sprite's size as in MAKES: a sprite may be 152x152 points in max. As a last point, the usage of GRAB is restricted to all the standard graphic modes known by the VGA-BIOS plus the "tweaked" 256 color mode used by ANIVGA itself. GRAB uses the BIOS-routines to read and write dots (with the exception of the tweaked mode of course) which makes it relatively slow (but reliable). As a consequence, you can capture from 16 color or monochrome graphic modes, too (although it makes little sense to me capturing 16 or 2 color images for usage in a 256 color sprite toolkit...) See also : MAKES GraphTextBackground, GraphTextColor, GraphTextOrientation - variables ───────────────────────────────────────────────────────────────────── Function : Determine how the OutTextXY()-procedures work Declaration: TYPE FontChar=ARRAY[0..5] OF BYTE; Font=ARRAY[0..255] OF Fontchar; FontOrient=(horizontal,vertical); CONST GraphTextOrientation:FontOrient=horizontal; GraphTextColor:BYTE=white; GraphTextBackground:BYTE=white; FontHeight=6; FontWidth=6; Description: Whenever text is to be written to the graphic screen, ANIVGA consults some global variables. GraphTextColor is simply the color in which the text should be drawn, GraphTextBackground specifies the color for the pixels in between the letters with one special value: if GraphTextBackground=GraphTextcolor, then only the pixels belonging to the letters will be drawn with all others remaining unchanged. Finally, GraphTextOrientation tells ANIVGA in which direction the text should be written with two values being possible: HORIZONTAL (default) for left-to-right text and VERTICAL for top-to-bottom style text. Note : Default color for the text is "white/white" = "white and don't change pixel values between letters". See also : OutTextXY, BackgroundOutTextXY HitDetect - function ──────────────────── Function : Checks whether two sprites collide or not Declaration: {$F+} FUNCTION Hitdetect(s1,s2:INTEGER):BOOLEAN; {$F-} Description: Call this routine with the sprite numbers of the two sprites to be checked for collision; the function will return TRUE/FALSE when the sprites collide/do not collide, respectively. Note (!) : - Collision detection is independent of whether the sprites are visible or offscreen: ANIVGA uses the corrdinates of the two sprites given (in SpriteX/Y) and internal data to check. - For this it is possible to check for collisions _before_ drawing an image (with Animate) and thus make necessary sprite updates at once! - Inactive sprites cannot collide: (SpriteN[s1] or SpriteN[s2]=0) -> FALSE - A sprite can't collide with itself: (s1=s2 -> FALSE) See also : Collision-detection InitGraph - procedure ───────────────────── Function : Initialises the VGA card for the use with ANIVGA Declaration: {$F+} PROCEDURE InitGraph; {$F-} Description: ANIVGA uses a special graphic mode, which supports 4 graphic pages in the resoultion 320x200 pixels and 256 colors. Because this mode is not known by the VGA's BIOS, ANIVGA has to reprogram the VGA. You should use this command only once to switch into graphic mode. Note : InitGraph automatically switches to the invisible graphic page 1-PAGE. See also : Screen, CloseRoutines InitRoutines - procedure ──────────────────────── Function : Resets all necessary internal variables of ANIVGA to initial values Declaration: {$F+} PROCEDURE InitRoutines {$F-} Description: At program start, some variables have to be set and a few system checks are necessary. Among these are: - SpriteN[] and SpriteAd[] become cleared (= set to 0) - Page (the actual drwaing page) is set to 0 - PageAdr is set to the segment address of the drawing page PAGE - BackgroundMode is set to STATIC, i.e.: non-scrollable background - BackGndAdr is set to the segment address of the background image - StartVirtualX/Y are set to (0,0), making the normal screen coor- dinates identical to the virtual screen coordinates - the old graphic/text mode which was active at program start is stored for restoring it at the program end - the system is checked if a VGA card is present and the global variable ERROR is set accordingly - CycleTime is set to 0, which says that there should be no time- control mechanism for the animation rate - if the machine is not at least an AT, the time mechanism is switched off completely - COLOR is set to 15 (= white) The first thing you should do in your programs is to look at the ERROR variable: if it was set to something different from Err_None (by the implicit, automatical call of InitRoutines) then your pro- gram should no proceed further. Note : - This routine is called automatically at the very beginning of every program which uses ANIVGA. For that, there is normally no need to call this routine explicitly. - Possible ERROR-values returned are: Err_None and Err_NoVGA - Note that this is the _only_ routine that definitely sets the variable ERROR, either to Err_None or Err_NoVGA. Because it is called at the beginning of every program, it is thus assured that your application always has a defined value for ERROR! See also : ERROR Line - procedure ──────────────── Function : Draw a line between the two points specified Declaration: {$F+} PROCEDURE Line(x1,y1,x2,y2:INTEGER; pa:BYTE); {$F-} Description: Calling this routine will draw a line between the two points (x1,y1) and (x2,y2) on graphic page "pa" and in the color COLOR. The routine uses virtual coordinates and clips the line down to its visible part. "pa" must be one of the values 0, 1 or BACKGNDPAGE (=2). Note : - As with all point-setting procedures of ANIVGA, you have to re- member ANIVGA's working scheme: the first thing ANIVGA does when Animate becomes executed is to copy the background image to the actual drawing page PAGE, erasing everything on that image. For this reason, a line drawn on the visible page 1-PAGE will be visible exactly one animation cycle. - Possible ERROR-values returned are: Err_InvalidPageNumber See also : PutPixel, BackGroundLine, coordinates LoadBackgroundPage - function ───────────────────────────── Function : Loads a background image from disk Declaration: {$F+} PROCEDURE LoadBackgroundpage(name:String) {$F-} Description: This routine loads a bitmap image stored in file "name" into the graphic page used for the background image (BACKGNDPAGE). Note (!) : - This routine must be called *after* the graphic mode has been initialized (with InitGraph())! - You can create such images either with the WritePage()- and WriteBackgroundPage()-routines of ANIVGA or the GRAB-Utility. - Calling this routine is equivalent to use the routine LoadPage() with BACKGNDPAGE as second argument. - Possible ERROR-values returned are: Err_FileIO and Err_NoPicture See also : Background, LoadPage, FillBackground, GetBackgroundFromPage, InitGraph LoadMAX - constant ────────────────── Function : Specifies the maximum number of different sprites Declaration: CONST LoadMAX=1000; Description: For each physical sprite, ANIVGA uses an internal pointer to its data. There are LoadMAX pointers, thus there may be up to LoadMAX different spriteLOADnumbers (= different sprites). Note : Don't mix this constant up with NMAX! See also : NMAX, SPRITE, SpriteLOADnumbers, Spritenumbers LoadPage - procedure ──────────────────── Function : Loads a graphic page from disk Declaration: {$F+} PROCEDURE LoadPage(name:STRING; pa:BYTE); {$F-} Description: "name" is the MSDOS-path to the graphic image to load, pa the destination page (0,1 or BACKGNDPAGE (=2)). Note : - The graphic mode must have been initialized (vià InitGraph) already! - You can generate disk files of graphic pages with the help of the WritePage()-routine or with the GRAB-utility program. - Don't use this routine to load an image into the SCROLLPAGE, i.e.: in background mode SCROLLING! - Possible ERROR-values returned are: Err_InvalidPageNumber, Err_FileIO and Err_NoPicture See also : GRAB, WritePage, background, InitGraph LoadSprite - function ───────────────────── Function : Loads one (or more) sprites into memory Declaration: {$F+} FUNCTION LoadSprite(name:String; number:WORD):WORD; {$F-} Description: "name" is the MSDOS-name of the sprite file to load, which can be either a single sprite file (*.COD) or a complete sprite library (*.LIB): the function will detect automatically, which format is used while loading the data. "number" is the spriteLOADnumber, the first loaded sprite will be assigned to. If the file contains more than one sprite, they will get consecutive LOADnumbers. The value returned by the function is the numbers of sprites read in (i.e.: 0 means "no sprite read", so you should check ERROR in that case). Note : - Unlike LoadTile(), LoadSprite() loads data into conventional memory. For that, you don't have to be in graphic mode to load data from disk! - Possible ERROR-values returned are: Err_FileIO, Err_NoSprite, Err_NotEnoughMemory and Err_InvalidSpriteNumber See also : sprite format, MAKES LoadTile - function ─────────────────── Function : Loads one or more tiles from disk Declaration: {$F+} FUNCTION LoadTile(name:STRING; number:BYTE):WORD; {$F-} Description: This routine loads the background tile file "name" into the graphic memory area reserved for tiles (the SCROLLPAGE). The starting number for the first tile of the file is "number", if there are more than one tile in the named file, they will be loaded too (with increasing numbers). The function returns the number of tiles read in. Note (!) : - This routine must be called *after* the graphic mode has been initialized (with InitGraph)! What the function actually does is reading in a sprite and con- verting it into an internal tile format: if the sprite read in doesn't have the proper size of a tile (16x16 pixels), you nor- mally will get an appropriate error (Err_NoTile), with one (use- ful) exception: if the sprite can be "cut" into tiles (that is, its width and height are multiples of 16 pixels each), then LoadTile() will do so with the following numbering scheme: from left to right and from top to bottom. For example, a sprite with (width,height)=(3*16,2*16) points would be numbered as: (assuming that "number" = 0) ┌────────┬────────┬────────┐ │ │ │ │ │ 0 │ 1 │ 2 │ │ │ │ │ ├────────┼────────┼────────┤ │ │ │ │ │ 3 │ 4 │ 5 │ │ │ │ │ └────────┴────────┴────────┘ Besides, LOADTILE can load a sprite library, too (they will be loaded in the sequence in which they appear in the library). - Possible ERROR-values returned are: Err_NotEnoughMemory, Err_FileIO, Err_NoTile and Err_InvalidTileNumber See also : Background, LOADSPRITE, TILE MAKES - utility ─────────────── The design of sprites is much to tedious to be carried out manually. For this reason, there are two utility programs to simplify that task. The first one is a resident program named "GRAB" to capture graphics from other applications and convert them into sprites, the second is MAKES, a _simple_ spritemaker program (don't expect too much). To use it, you must have a mouse installed (and a VGA card, of course). (Other than ANIVGA itself, the program uses the "normal" 256-color mode $13, so a MCGA-adapter should work also) There are no parameters or such things, just start it! In the upper right region of the screen there is the so called "work area", in which you can paint your sprite pixelwise. At the bottom of the screen, all possible colors are available. To choose one, point at the color wanted and press the mouse button, to which you want this color assigned. All other options are so simple that there should be no descriptions necessary, so that I only give some general infos here: Note that sprites are always stored as the smallest rectangle which surrounds them and starts at the upper left corner (0,0): if you don't have special reasons to do otherwise, your sprites should start in the upper left corner. If for example you realize a sprite consisting of one single point at coordi- nates (a,b), the smallest surrounding box with (0,0) as upper left corner would be (0,0) (a,0) of size (a+1)*(b+1) pixels (=bytes)!!! ┌──────────┐ │ │ │ │ │ │ └──────────▀ <─ this is your 1 point (0,b) (a,b) To determine what areas belong to your sprite and which don't, the program assumes color 0 to specify no-sprite-areas and all other colors to be part of your sprite (roughly spoken). The best way to design a sprite is to start with a cleared work area and draw the sprite in the midst of it. If you think you're done, use the direction boxes to align your sprite with the upper left corner. Then click on the "boundaries" option ("see transparent?": no) to see the sprite's size and extension in the x/y-directions. This is useful to find very dark points with color<>0 set accidentally which would extend the sprite size unnecessarily. If you are unsure whether you can use display mode "Display_FAST" or not, call "boundaries" a second time and select "see transparent?" _yes_ this time: if the blinking white parts "spread" out of the parts you think your sprite should be made of, then you should use "Display_NORMAL", if all the blinking areas are inside your sprite, you can use "Display_FAST". Note: - The maximal size for your sprites developped this way is 152x152 points (that is only because of the restricted size of the work area on your screen; ANIVGA itself can handle sprites up to 32000 pixels in each axis or 64K max. size) - For more complex sprites, it is often easier to use a commercial pain- ting program, capture the sprite with GRAB and edit the resulting sprite with MAKES See also: sprite format, GRAB, Display modes MaxTiles - constant ─────────────────── Function : Holds the maximum number of tiles to build the background image Declaration: CONST MaxTiles=10000; Description: In background mode SCROLLING, you may use up to MaxTiles tiles to build your graphic image. Note : - See also : Background NextSprite - variables ────────────────────── Function : Holds the "successors" of sprites for sprite cycles Declaration: VAR NextSprite: ARRAY [0..LoadMAX] OF WORD Description: To realize a sprite cycle, you must tell ANIVGA which sprites should be drawn one after another. It is this information NextSprite holds! For example, let us assume that you wanted to make the sprite(loadnumber)s 43, 177 and 111 a sprite cycle, i.e.: whenever you set a sprite (to be precise: a SpriteN[]-entry) to one of these three numbers, ANIVGA should cycle between the three sprite-images in the sequence 43->177->111->43->177->111->... You would then set NextSprite[43]:=177; NextSprite[177]:=111 and NextSprite[111]:=43 (don't forget this final value!) to do so. Note (!) : - Most often, you will have the situation that some sprite(load)- numbers with consecutive numbers should make up a cycle. In that case it is more convenient to use the SetSpriteCycle()-procedure to do the job for you - Again, note that the routine deals with spriteLOADnumbers! That is intentionally, because a sprite cycle is related to the _physical_ existent sprite data, or simply spoken: if you make 5 pictures to form a flickering torch and you are going to use 10 torches in your animation then each of them should loop through this 5-picture-cycle, shouldn't it? - NextSprite[] is initially set "to point to itself", that is: NextSprite[i]=i for all possible i's. If you had to break off a sprite cycle (though I can't think what this should be good for...), you must restore this data, e.g.: if you wanted to break the sprite cycle above, you would have to set NextSprite[43]:=43; NextSprite[177]:=177; NextSprite[111]:=43; - As this is a global variable, ANIVGA can't check whether your settings make sense or not; thus, it remains your responsibility to use proper values! See also : SetSpriteCycle, Sprite cycles NMAX - constant ─────────────── Function : Determines the maximum of sprites to be active at the same time (minus 1) Declaration: CONST NMAX=499 Description: This constant sets the size of the internal tables - and thus the valid sprite numbers: the indices of the tables SpriteX, SpriteY and SpriteN must lie in the range 0..NMAX. To state it otherwise, there may be up to NMAX+1 sprites creeping around your screen at the same time... Note : Don't confound that constant with LoadMAX See also : LoadMAX OutTextXY - procedure ───────────────────── Function : Writes a textstring to the graphic screen Declaration: {$F+} PROCEDURE OutTextXY(x,y:INTEGER; pa:BYTE; s:STRING); {$F-} Description: ANIVGA has a built-in font, each character consisting of 6x6 pixels: very ugly, but hey, we want to make animations, not text! To write the string "s" to the graphic screen, you must specify the upper left starting corner of the text in (x,y): (x,y) -> ▄──────────┐ , where (x,y) are virtual coordinates! │ │ │ │ │ │ └──────────┘ The text will be drawn in color GRAPHTEXTCOLOR and with the orien- tation GRAPHTEXTORIENTATION ("VERTICAL" or "HORIZONTAL"). A third global variable, GRAPHTEXTBACKGROUND, specifies the color which will be used for the background area "beneath" the text letters; if GRAPHTEXTCOLOR=GRAPHTEXTBACKGROUND then the text will be drawn like TurboPascal's routine does: only the pixels be- longing to the letters will be drawn, all others remain unchanged. "pa" specifies the graphic page to be drawn on and must be one of the drawing pages (0 or 1) or the BACKGNDPAGE (=2) for background mode STATIC. Note : - Better fonts could have been developped, but they would all depend on special assumptions about the text- and/or background color(s). This font was intented for short and simple text strings and to be as small as possible. Nevertheless, using a bigger cell (say: 10x10) and several colors (for antialiasing effects) can result in very impressive fonts - and work, too... - Possible ERROR-values returned are: Err_InvalidPageNumber See also : GraphtextColor, GraphtextOrientation, GraphtextBackground, BackgroundOutTextXY PAGE - variable ─────────────── Function : Holds the number of the actual drawing page Declaration: VAR PAGE:WORD Description: ANIVGA uses a page flipping approach. Basically this means that it alternates between using page 0 and page 1 for its display. Although this mechanism should be transparent for the user, ANIVGA provides you with the page number of the actual drawing page in "PAGE". Note that this number specifies always the invisible page: when PAGE=0, then the actual _displayed_ page is page 1 and vice versa (ANIVGA always works on the invisible page!). Note (!) : Only _read_ this value, never assign a new value to it! PAGEADR - variable ────────────────── Function : Holds the segment address of the actual drawing page PAGE Declaration: VAR PAGEADR:WORD Description: As already mentioned, there are four graphic pages, numbered from 0 to 3. The start addresses of these four pages are used by ANIVGA and normally the user should not need to reference them, but with PAGEADR at least the address of the actual (invisble) graphic page PAGE is available in PAGEADR. Note (!) : Only use this variable to _read_ its value, never change it! Although this 16-bit-value represents only the segment part of the complete address, it is the whole address: the address is norma- lized in such a way that the offset part is always zero. See also : PAGE PageGetPixel - function ─────────────────────── Function : Returns the color value of the specified point Declaration: {$F+} FUNCTION PageGetPixel(x,y:INTEGER; pa:BYTE):BYTE; {$F-} Description: If the point at the virtual coordinates (x,y) and graphic page "pa" lies on the screen (i.e.: in the range (0,0)..(319,199) in absolute coordinates), this routine will return its color, if it is offscreen, the function returns zero. "pa" should be one of the values 0, 1 or BACKGNDPAGE (=2). Note : - If you want to read a pixels' color from the _visible_ page, you have to remember that it is the opposite of the _actual_ page (that is, you have to use "1-PAGE" as page number). - Although only values of 0,1 and BACKGNDPAGE (=2) make sense as "pa" values, the routine doesn't check that (for improved speed) - For that, the routine _doesn't_ return Err_InvalidPagenumber or something similiar in ERROR! See also : Background, Coordinates, GetPixel PagePutPixel - procedure ──────────────────────── Function : Plots a point at a specified page Declaration: {$F+} PROCEDURE PagePutPixel(x,y:INTEGER; color,pa:BYTE); {$F-} Description: This routine is very similiar to PutPixel(), but it lets you specify explicitly on which graphic page the point shall be drawn. (x,y) specify the virtual coordinates of the point to be drawn in color "color". If this point lies onscreen (i.e.: its absolute coordinates are between (0,0)..(319,199)), it will be drawn on the specified page "pa", which must have one of the values 0, 1 or BACKGNDPAGE (=2). The latter only makes sense if STATIC is used as background mode. Note : - Don't forget that this routine works with virtual coordinates. - Note also that the point is _not_ drawn automatically on the background page if pa=0 or pa=1, thus it will be visible exactly one animation cycle (and be overdrawn by the background image then). - Because of ANIVGA's working scheme, you probably want to use this routine AFTER calling Animate() (else, your point would be overdrawn by the background image immediately) if pa=1-PAGE. If you want to draw the point at the _visible_ page, remember that it is the "opposite" of the _actual_ drawing page, i.e.: you have to use "1-PAGE" for "pa". - For improved speed, the routine _doesn't_ check the "pa" variable to have a valid value, so there will be no report to ERROR (Err_InvalidPageNumber or the like) available! It remains your responsibility to assure a proper value for pa! See also : BackgroundPutPixel, PutPixel, coordinates, How ANIVGA works PutImage - procedure ──────────────────── Function : Pastes a formerly copied image to the screen Declaration: {$F+} PROCEDURE PutImage(x,y:INTEGER; p:POINTER; pa:WORD); {$F-} Description: PutImage() is the counterpart of GetImage(): use GetImage() to copy part of the screen and PutImage to paste it somewhere. (x,y) is the upper left corner of the destination (in _virtual_ coordi- nates), "p" is the pointer given by GetImage() and "pa" is the number of the graphic page (0, 1 or BACKGNDPAGE (=2)) of the des- tination. If p equals NIL, the routine does nothing at all; this is useful because you can PutImage() directly on the result of a GetImage() call without further checking for clippings. Note : - Like GetImage(), this routine also works only when the _virtual_ coordinates translate into _absolute_ coordinates in the range of 0..319, 0..199, that is: they must lie on the visible part of the screen, everything else is clipped off. - Possible ERROR-values returned are: Err_InvaliPageNumber See also : GetImage, coordinates PutPixel - procedure ──────────────────── Function : Plots a point Declaration: {$F+} PROCEDURE PutPixel(x,y:INTEGER; color:BYTE); {$F-} Description: (x,y) specify the virtual coordinates of the point to be drawn in color "color". If this point lies onscreen (i.e.: its absolute coordinates are between (0,0)..(319,199)), it will be drawn on the visible page 1-PAGE. Note : This routine is not the same as TurboPascal's one: it works with virtual coordinates! Note also that the point is _not_ drawn on the background page, thus it will be visible for exactly one ani- mation cycle (and be overdrawn by the background image then). Because of ANIVGA's working scheme, you probably want to use this routine AFTER calling Animate() (your point will then be visible until the next call to Animate()). See also : BackgroundPutPixel, PagePutPixel, coordinates, How ANIVGA works PutTile - procedute ─────────────────── Function : "Pastes" a tile into the background image Declaration: {$F+} PROCEDURE PutTile(x,y:INTEGER; TileNr:BYTE); {$F-} Description: After you have defined a background scrolling area, you can use to PutTile() to arrange them as wanted to build your background image. (x,y) is the virtual coordinate where you want the tile "TileNr" to be placed. (x,y) will be changed to be a multiple on 16 in each direction and must then lie in the range (BackX1,BackY1)..(BackX2,BackY2). Note : - Of course, this routine only makes sense when you use background mode SCROLLING! - (x,y) will be drawn to the upper left to fall on the grid. - Possible ERROR-values returned are: Err_InvalidCoordinates See also : background, tile, SetBackgroundScrollRange, coordinate, BackX1, BackX2, BackY1, BackY2 Screen - procedure ────────────────── Function : Chooses the display page. Declaration: {$F+} PROCEDURE Screen(pa:BYTE) {$F-} Description: Call Screen() with a value between 0 and 3 which tells the routine to which graphic page it should switch. This is done by repro- gramming the VGA start address registers. For a flickerfree dis- play, this switching is synchronized to the vertical retrace signal. Note (!) : - You should not use this routine if you are not absolutely sure what you are doing! Be aware that ANIVGA relies on the fact that the actual drawing page is PAGE and its segment address is in PAGEADR while the visible page is 1-PAGE! - Although it makes little sense to apply this routine to graphic pages other than 0 or 1, it is possible to set "pa" to 2 (=BACK- GNDPAGE) or 3 (=SCROLLPAGE). See also : PAGE, PAGEADR, InitGraph ScrollPage - constant ───────────────────── Function : Holds the page number of the backround page Declaration: CONST SCROLLPAGE=3; Description: When using background mode SCROLLING, BackGndPage specifies the page number of the tile buffer used to build up the background image for animations. Note (!) : Use of this constant only makes sense when using background mode SCROLLING! See also : BackGndPage, Background SetBackgroundMode - procedure ───────────────────────────── Function : Chooses one of the possible background modes of ANIVGA Declaration: {$F+} PROCEDURE SetBackgroundMode(mode:BYTE); {$F-} Description: ANIVGA has two possible ways of handling background you can choose of: "STATIC" or "SCROLLING" backgrounds with several advantages and disadvantages, each (see background). Specify the mode you want to use in the "mode" variable. Note : - Default value set by ANIVGA is STATIC. - Possible ERROR-values returned are: Err_InvalidMode See also : background SetBackgroundScrollRange - procedure ──────────────────────────────────── Function : Specifies the scrollable background area in mode SCROLLING Declaration: {$F+} PROCEDURE SetBackgroundScrollRange(x1,y1,x2,y2:INTEGER) {$F-} Description: (x1,y1) is the upper left corner of the background scroll area, (x2,y2) the lower right corner (all virtual coordinates). ANIVGA will round the points given to fit on a grid with mesh 16, that is, x1,y1,x2,y2 will be changed to be all multiples of 16. These new values will be stored in the (global) variables BackX1, BackY1, BackX2, BackY2 for further use. Besides that, XTiles and YTiles will hold the width and height of the choosen background area in tiles. Note : - You can read the Back??-variables for your information, but don't change them! - Of course, this routine only makes sense when you are going to use SCROLLING as background mode. - The upper left corner (x1,y1) will be drawn to the upper left, the lower right corner (x2,y2) to the lower right to fall on the grid. - Don't forget that the tile memory is limited; you can't select an area bigger than MaxTiles (=10000) tiles, that is more than 2560000 pixels². - Possible ERROR-values returned are: Err_InvalidCoordinates and Err_BackgroundToBig See also : background, tiles, PutTile SetCycleTime - procedure ──────────────────────── Function : Defines the maximum animation speed Declaration: {$F+} PROCEDURE SetCycleTime(milliseconds:WORD); {$F-} Description: There are lots of PC-compatible machines with a broad range of clock rates, wait states and different speeds of their graphic cards. With this routine you can set the time an animation cycle has to last at least: at the very end of Animate, the routine checks whether at least "milliseconds" milliseconds have been past since the last call to this routine and waits if necessary. If you give 0 milliseconds as an argument or your machine is not (at least) an AT class machine, there will be no such time control mechanism and the animation will always take part at the maximal speed on the specific machine (this is also the default value). For example: "SetCycleTime(100);" would restrict the animation rate even on the fastest 80586 machines to at most 1sec/100msec = ten frames per second. Note (!) : - Because there is no such high precision timer on PC/XT computers as required, SetCycleTime() is ignored on these machines. Anyway, this should be not to hard because these computers are normally that slow that they would not have been slowed down either. - The accuracy of this timing mechanism is better than 1 milli- second. SetModeByte - procedure ─────────────────────── Function : Specifies the way a sprite will be displayed Declaration: {$F+} PROCEDURE SetModeByte(Sp:WORD; M:BYTE); {$F-} Description: This routine assigns one of the possible display methods "M" (Display_NORMAL, Display_FAST, Display_SHADOW) to the specified spriteLOADnumber "Sp". Note : - Because this kind of information is stored directly inside the sprite data, the sprite must have been loaded already for this action to work. - For the same reason, this routine works on spriteLOADnumbers, not sprite numbers (>gee, again!<): a display method set for one spriteLOADnumber will affect all sprites with that LOADnumber! Most often, that is okay (e.g.: if you use the sprite of a foot- ball player ten times, it is quite normal to use the same dis- play mode for all ten players!), if you really must use a sprite with two different display methods at the same time, you can use the following trick: load the sprite's data a second time into memory, using a different spriteLOADnumber. For this second copy, you can use another display mode. - Possible ERROR-values returned are: Err_InvalidSpriteNumber and Err_InvalidMode See also : SpriteLoadNumber, SpriteNumber, Display methods, GetModeByte SetShadowTab - procedure ──────────────────────── Function : Set the amount of shadowing in display mode "Display_SHADOW" Declaration: {$F+} PROCEDURE SetShadowTab(brightness:BYTE); {$F-} Description: Whenever a sprite is drawn in "Display_SHADOW" mode, ANIVGA must know how much darker these shadow areas should be, compared with the brightness of the original (not-shadowed) colors. These data is held in the table ShadowTab and is set to 70% of the colors original brightness. However, you can use this routine to provide more or less darker shadow areas: "brightness" is the percentage of the colors original brightness which shall remain, e.g.: brightness=0 would mean every shadow is completely black, brightness=100 is the original color as shadow (not darkened at all), brightness=40 will darken every color by 100-40=60%, etc. Note (!) : - This routine takes quite a long time (app. 4s on an 8MHz AT). - The argument will be only approximated: the algorithm computes the 256 color values needed precisely and matches them as close as possible to the 256 default colors of graphic mode $13. Note that the palette registers of the VGA card *won't* be changed at all! ANIVGA still works with the standard VGA palette of the BIOS; what it does is solely creating a color look-up- table! - Possible ERROR-values returned are: Err_InvalidPercentage See also : ShadowTab, Display modes, SetModeByte SetSpriteCycle - procedure ────────────────────────── Function : Links spriteLOADnumbers together to form a sprite cycle Declaration: {$F+} PROCEDURE SetSpriteCycle(nr,len:WORD); {$F-} Description: "nr" is the first spriteLOADnumber to be included in the sprite cycle and "len" entries (i.e.: from "nr" to "nr+len-1") should be tied together. The routine will then set the according NextSprite[] entries to build this cycle: nr -> nr+1 -> nr+2 -> ... -> nr+len-1 -> nr Note : - The routine uses spriteLOADnumbers, _not_ sprite numbers! - If you want to link sprite(loadnumber)s which do not have conse- cutive (load)numbers, you must do that by setting NextSprite[] accordingly. See also : Sprite cycles, NextSprite ShadowTab - "procedure" ─────────────────────── Function : Table for translating sprite colors into others Declaration: {$F+} PROCEDURE ShadowTab; {$F-} Description: If the display mode "Display_SHADOW" is set for a physical sprite, its colors will depend not on the values stored in the sprite it- self, but on the values found on the screen at the place where the sprite shall be drawn: every pixel of the sprite will become dar- kened by substituting its corresponding color against the color stored in this color table. At startup, this table is set to make shadows be approximately 70% the brightness of the original colors, but you can adjust this with the routine SetShadowTab() if this default is not suitable for your application. You can even supply a completely different color table (for special effects?). To do so, define an array "[0..255] of byte" (you can use the pre- defined TYPE ColorTable for this), containing for each color of the standard palette its substitute (e.g. setting array element [8]:=13 would mean: "replace every pixel in the shadow area with color 8 against a pixel with color 13") and overwrite the original color table by issuing the command "MOVE(my_array,@ShadowTab^,256)" Note : - Although this table is declared as a procedure, it really is data, not code; so don't call it! - There can be only _one_ color table and it is only active in display mode "Display_SHADOW". See also : SetShadowTab, Display modes, SetModeByte SPRITE, Spritenumbers, Spriteloadnumbers - information ────────────────────────────────────────────────────── A sprite is the basic data element used in ANIVGA. Technically spoken, it is nothing more then a two-dimensional array of bytes which becomes copied to the screen positions needed, but it is far more comprehensive to think about it as a photograph of a figure which can be pasted to the screen whereever you want. To distinguish between different sprites, we use natural numbers, but whenever we talk about "sprites", we are somehow inaccurate: You should notice that there are two kinds of "sprite numbers" which should not be mixed up: one is a spriteLOAD number and represents a handle to the (physical) sprite data, while the other (normally termed "sprite number") is a logical number to address the sprite data. Yet, most often it is clear from the context, which meaning is intended: For a simple example: if you are going to animate a soccer team, you would need 11 sprites for the player - but they all have the same shape. This means, you only have to load one sprite (-> you need 1 spriteLOAD number), but need 11 copies of that to move around the screen (-> you need 11 sprite numbers). (See section "How ANIVGA works" for more about that) You can design sprites with the help of the spritemaker-tool MAKES, by using GRAB to capture and convert graphic screens from other graphic applications or write your own tools for that (it's really not that difficult you think now it would be...). See also : sprite format, How ANIVGA works SPRITE CYCLES - information ─────────────────────────── Often, you don't want to have a single picture as sprite, but a sequence of them which should loop forever. For example, let's assume that you use a torch as an animation object in your application and you want it to have a flickering flame. You would start to draw 5 (say) pictures, which -repeatedly displayed one after another- would make the impression of your flickering torch. But within your application, you still want to handle these five different images as one single object - namely the sprite "torch". To do so, you can use a capability of ANIVGA, called a "sprite cycle": load the five images as (physical) sprites and tie their loadnumbers together to form that sequence! The easiest way to do that would be to load the images with consecutive numbers and use the SetSpriteCycle() procedure to form the sprite cycle (see there). Note that we are talking about linking spriteLOADnumbers here: when you have built such a cycle for your torch and you want to use 10 torches in your program, you surely want that each of them behaves the same, that is: they all should show a flickering flame by using that sprite cycle. For this reason, ANIVGA uses spriteLOADnumbers, so that every instantiation of a spriteLOADnumber (i.e.: a SpriteN[]-entry) belonging to a cycle will lead to a sprite cycle for this sprite! A small detail at last: if you defined a sprite cycle to be a->b->c->a->..., and initialized a SpriteN[]-entry to "a", then the first sprite displayed at the screen will be "b" instead of "a" - why? Well, ANIVGA handles sprite cycles in the Animate() routine and thus has two possibilities to update the SpriteN[]-table (by issuing a "SpriteN[] := NextSprite[SpriteN[]]" command): _before_ drawing the sprites or _afterwards_. But when it does _after_ drawing the sprites, the sprites displayed on your screen (=the old SpriteN[] values before doing the above command) are inconsis- tent to the according numbers actually held in the SpriteN[]-table! This could lead to problems (e.g.: when you do a HitDetect() after calling Animate()). Although this could be circumvented by a special grouping of sub- routine calls, it is far more convenient to update the SpriteN[]-table _before_ drawing the sprites. The only drawback with this method is the one stated in the beginning: not the SpriteN[]-entry supplied by you will be drawn, but its "successor" NextSprite[SpriteN[]]! However, most often that won't be that bad and *if* it would, you still could compensate for it by using the sprite's predecessor (in the above example, you would use "c", as it is the predecessor of "a", to display "a"). SPRITE FORMAT - information ─────────────────────────── As already said, a sprite is nothing more then a two-dimensional array of bytes which becomes copied to the screen positions needed. For quick animations, the data should be stored in a format which causes few and simple transformation steps when accessing the data, but it is hard to keep up with that principle, because the graphic mode used is "planed". This means that points are _not_ stored sequentially into the graphics memory, but in a rather strange way: every 4 points use the same address, but lie in different "bitplanes". To cut it short: clipping and drawing sprites is hell therefore (and surely one reason why there are so less tools for this mode) and ANIVGA uses a very special format to store a sprite (= *.COD-files): 0..1 DW offset to Plane_0_Data (points with x-coord. MOD 4=0) 2..3 DW offset to Plane_1_Data (points with x-coord. MOD 4=1) 4..5 DW offset to Plane_2_Data (points with x-coord. MOD 4=2) 6..7 DW offset to Plane_3_Data (points with x-coord. MOD 4=3) 8..9 DW sprite width (DIV 4), rounded up if not dividable by 4 10..11 DW sprite height in lines 12..15 DB 1,2,4,8 ; constants (translate-table) 16..17 DW SpriteLength ; length of this sprite file 18..37 DW 10 dup(?) ; reserved area for future use 38..39 DB 'K','R' ; code for "this is a sprite file" 40 DB 1 ; version 41 DB 0 ; default display mode (0=Display_NORMAL) 42..43 DW offset pointer to left boundary table 44..45 DW offset pointer to right boundary table 46..47 DW offset pointer to top boundary table 48..49 DW offset pointer to bottom boundary table 50..SpriteLength-1: boundary- and plane data tables (If you should wonder why all pointers are only 16 bit long: the maximal size of one sprite is 64k, so offset pointers are sufficient. Another trick is that ANIVGA loads sprites at segment boundaries; for that, you don't have to distinguish between "relative offsets" and "offset poin- ters": if normalized segment addresses (=offset part is ε [0..15]) are used to address sprites, the offset part is always 0, so the two terms are identical!) The Plane_?_Data tables consist of the points of the sprite (1 pixel = 1 byte); if the sprite width is 12 pixels (say), then each table would hold 12/4=3 bytes for each of the sprite's rows: Plane_0_Data = color of pixels 0,4,8 of 1. sprite row color of pixels 0,4,8 of 2. sprite row ... Plane_1_Data = ditto, for pixels 1,5,9 Plane_2_Data = ditto, for pixels 2,6,10 Plane_3_Data = ditto, for pixels 3,7,11 The boundary tables hold the outermost positions of the sprite: The left/top/right/bottom boundary table holds the leftmost/topmost/rightmost/ bottomost pixel of each row/column/row/column (or 16000/16000/-16000/-16000 if none exists), respectively: left boundary table = leftmost pixel coordinate of 1. sprite row (or 16000) leftmost pixel coordinate of 2. sprite row (or 16000) ... Note that each entry in the boundary tables consists of a signed integer! Note also that sprites are always stored as the smallest, the figure including box (rounded up in the x-direction to the next multiple of 4), but that the values of the "superfluous points" stored in the plane tables doesn't matter at all (no difference which display mode is used for the sprite!), because ANIVGA uses only the bytes of the areas which belong to the _real_ sprite-figure (ANIVGA determines this parts by assuming the sprite to be "horizontal convex" and uses the boundary tables to compute them). (Don't worry if you do not understand these technical details now -- hopefully, you won't need them at all). See also : MAKES, Display modes, convex, sprite library SPRITE LIBRARY - information ──────────────────────────── Sprite files can be combined to sprite libraries. The main advantage of this is that you can reduce the number of files needed for your programs dramatically: A normal program will use approximately 20..40 different sprites, so that you would have 20..40 files only for your sprites! But ANIVGA's routine to load sprites "loadSprite()" is flexible enough to dis- tinguish whether the file to be loaded contains one or more sprites and loads them all. To construct such a "sprite library" (suggested filename extension: .LIB), you just use MSDos' COPY-command with the binary option "/B"; for example: COPY /B sprite1.cod+d:\sprites\sprite2.cod+testspr.cod A:\mylib.lib would concatenate the three sprites "sprite1.cod", "d:\sprites\sprite2.cod" and "testspr.cod" and build the sprite library "A:\mylib.lib". You can reverse this process with the UNLIB-utility. See also : UNLIB, sprite format, loadSprite SpriteAd - variable ─────────────────── Function : Store the pointers to the sprites' data Declaration: VAR SPRITEAD:ARRAY[0..LoadMAX] OF WORD; Description: Whenever you load a (physical) sprite with LOADnumber xxx, ANIVGA stores the sprite's data somewhere in RAM and maintains a pointer which points to the beginning of this data as a handle to access the data: this handle is stored in SpriteAd[xxx] and reflects the segment part of the starting address of the data. Note : Don't change that data directly unless you are absolutel sure what you are doing! See also : LoadSprite, SPRITE, Sprite Format SPRITEN, SPRITEX, SPRITEY - tables ────────────────────────────────── Function : Hold the values of all sprites to be drawn in the next animation cycle. Declaration: VAR SpriteN:ARRAY[0..NMAX] of Integer (SpriteX/Y dto.) Description: ANIVGA is based on tables: in SpriteN[] you must declare, which sprites shall be drawn in the next animation step. To do that, store the spriteLOAD number of the sprites into the SpriteN[]- entries; a zero indicates that the according sprite is inactive and should not be displayed. For every active sprite (SpriteN[i]<>0), a pair of virtual coor- dinates in the range -16000..+16000 must be specified in the SpriteX[i] and SpriteY[i] entries to determine the sprites' po- sition on the (virtual) screen. These coordinates will be transformed internally into real coor- dinates to decide whether the sprite is onscreen and has to be displayed or not. Note : If you have less sprites than are allowed by the system (that is: less than NMAX+1), your decision what table entries you use are arbitrary; if for example you have only two sprites, it won't matter, if you use SpriteN[0] for the first one and SpriteN[1] for the other or vice versa, or SpriteN[123] and SpriteN[310] or whatever valid indices you can think of - except in one point: the sprites are drawn in reverse order, that means SpriteN[NMAX] is drawn first, then SpriteN[NMAX-1] ... SpriteN[0]. For that, if two (or more) sprites overlap each other, the one with the smallest index is drawn topmost and covers the other(s). For performance reasons you should observe another rule: if you use different display methods for different sprites then try to group your sprites in such a way, that sprites with the same dis- play method have continous indices. As an example: if the sprites with (load)number 1 use one method and the ones with number 2 another, then the sequence SpriteN[]=(...2,2,2,2,2,...,1,1,1...) would be better than (...2,2,1,2,...,1,2,...,1,2,...). This is due to the fact that whenever ANIVGA has to draw a sprite with a display method other than the active one, it must inter- nally switch from one method to the other which costs some time. See also : SetModeByte StartVirtualX, StartVirtualY - variables ──────────────────────────────────────── Function : Specify the upper left corner of the visible world Declaration: CONST StartVirtualX:INTEGER=0; StartVirtualY:INTEGER=0; Description: When working with virtual coordinates, your screen displays only a very small window (320x200 points) of this "virtual screen" (32000x32000 points). To tell ANIVGA which part of this virtual screen is to be displayed, you specify the upper left corner of the visible part in (StartVirtualX,StartVirtualY). For example, setting (StartVirtualX,StartVirtualY) to (100,1000) would define that the part of the virtual screen having x-coordi- nates ε [100..100+XMAX] and y-coordinates ε [1000..1000+YMAX] to be displayed. Note : Setting these variables doesn't affect the HitDetect-function: if two sprites collide outside the visible area, it will be detected, still. See also : coordinates Table - TYPE ──────────── Function : Supply a data type for the animation variables Declaration: TYPE Table=ARRAY[0..NMAX] OF INTEGER; Description: A lot of variables in ANIVGA have to be of type "one entry for each sprite" and "Table" is the appropriate form for that. Note : - See also : SpriteX, SpriteY, SpriteN Tile - information ────────────────── "Tiles" are graphic images, 16 pixels wide and high. They are used to define a scrollable background image when you use SCROLLING as background mode. Due to memory limitations, it is impossible to hold a complete background image in memory (because virtual coordinates range 32000 pixels in x/y-directions, one would need app. 977 MB (!) RAM for that). Instead, you may define up to 256 different tiles and then combine them to form the graphic background, which may consist of up to MaxTiles (=10000) tiles (using the 256 different tiles). (A simple example for that can be found by "Background"). ANIVGA stores tiles in a slightly different format then sprites internally, but you don't have to bother your head about that: on disk, tiles have the same format as sprites, so you can use all the utility programs to create/edit sprites also to create/edit tiles! The only restriction you have to care about is, that a tile has the definite size of 16 pixels in each direction (but see the LoadTile()-function for some simplifications about even that). See also : Background, LoadTile UNLIB - utility ─────────────── Sometimes, you will want to reverse the process of building a sprite library, that is: you want to split a sprite library into the sprite files of which it consists. To do that, call UNLIB with the name of the sprite library to split. UNLIB will then create the files UNLIB000.COD, UNLIB001.COD, UNLIB002.COD,... which re- present the sprite files wanted. Note here that UNLIB cannot restore the original filenames you used (there is no such entry in a sprite's header). For that, it is a good idea to write down the names and sequence of the sprite files used in building a sprite library. (If you didn't, you still can load every extracted sprite with MAKES, look at it and give it the right name then) See also : sprite library, MAKES, sprite format VIRTUAL COORDINATES - information ───────────────────────────────── See : coordinates WriteBackgroundPage - procedure ─────────────────────────────── Function : Saves the background image to disk Declaration: {$F+} PROCEDURE WriteBackgroundPage(name:STRING); {$F-} Description: This is merely a shortcut of the WritePage()-procedure (see there), i.e. WritePage(name; BACKGNDPAGE) would do an equivalent job. Note : Possible ERROR-values returned are Err_FileIO See also : WritePage WritePage - procedure ───────────────────── Function : Saves a graphic page to disk Declaration: {$F+} PROCEDURE WritePage(name:STRING; pa:BYTE); {$F-} Description: To save an image of one of the drawing pages (0 or 1) or the back- groundpage BACKGNDPAGE (=2), specify the approriate page number in "pa" and a valid MSDOS-path/name where to store the data in "name". Note : - Make sure that your disk has enough space to hold the data: one page is stored as 64003 bytes! - You can't use this procedure for saving the background page "pa" =SCROLLPAGE in background mode SCROLLING! - Possible ERROR-values returned are: Err_InvalidPageNumber and Err_FileIO See also : WriteBackgroundPage, LoadPage XMAX - constant ─────────────── Function : Specifies the maximal absolute x-coordinate Declaration: CONST XMAX=319 Description: XMAX is the biggest _absolute_ coordinate in the x-direction which can be used: all x-coordinates must lie in the range 0..XMAX. Note : Probably, you will never use this constant at all, because nearly everything in ANIVGA's user interface works with _virtual_ coordi- nates, but who knows... See also : YMAX, coordinates XTiles - variable ───────────────── Function : Holds the width of the scrollable background image in tiles Declaration: VAR XTiles:INTEGER; Description: When using background mode SCROLLING, you have to specify the size of your scrolling background area (with the SetBackgroundScroll- Range()-procedure). ANIVGA adjusts these values slightly and computes the size of the resulting background image in tiles. The width of this area (in tiles) is then stored in XTiles. Notes : Don't change this variable directly! See also : YTiles, Background, SetBackgroundScrollRange YMAX - constant ─────────────── Function : Specifies the maximal absolute y-coordinate Declaration: CONST YMAX=199 Description: YMAX is the biggest _absolute_ y-coordinate which may be used, that is, every y-coordinate must lie in the range 0..YMAX. Note : Probably, you will never use this constant at all, because nearly everything in ANIVGA's user interface works with _virtual_ coordi- nates, but who knows... See also : XMAX, coordinates YTiles - variable ───────────────── Function : Holds the height of the scrollable background image in tiles Declaration: VAR YTiles:INTEGER; Description: When using background mode SCROLLING, you have to specify the size of your scrolling background area (with the SetBackgroundScroll- Range()-procedure). ANIVGA adjusts these values slightly and computes the size of the resulting background image in tiles. The heigh of this area (in tiles) is then stored in YTiles. Notes : Don't change this variable directly! See also : XTiles, Background, SetBackgroundScrollRange