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Info file: geomview, -*-Text-*- produced by texinfo-format-buffer from file: geomview.tex File: geomview Node: Top, Up: (DIR), Next: What * Menu: * What:: What is Geomview?. * Authors:: The Authors of Geomview. * Register:: Let Us Hear From You. * Overview:: Overview of Geomview. * Tutorial:: Introductory Tutorial. * Interaction:: Interacting with Geomview. * OOGL File Formats:: Formats for Geometry Input. * Customization:: Modifying the behavior of Geomview. * Modules:: Programs that use Geomview for graphics display. * GCL:: gcl: the Geomview Command Language. * Mathematica:: Mathematica Graphics in Geomview or RenderMan. * Installation:: Installing Geomview on your computer. * Function Index:: A node for each gcl function. File: geomview Node: What, Prev: Top, Up: Top, Next: Authors What Is Geomview? ***************** Geomview, pronounced GE-om-view, is an interactive program for viewing and manipulating geometric objects, written by staff members of the Geometry Center. It can be used as a standalone viewer for static objects or as a display engine for other programs which produce dynamically changing geometry. It runs on Silicon Graphics (SGI) IRIS workstatons and NeXT workstations. This manual describes SGI Geomview version 1.4.1. Although we do not yet have a manual for the NeXT version, much this of manual applies to that version as well as to the SGI version. Geomview and this manual are available for free via anonymous ftp on the Internet from host `geom.umn.edu' (IP address 128.101.25.35). Permission is granted to make copies of this manual. If you have questions or comments about Geomview or this manual, you can email them to `software@geom.umn.edu'. We are always glad to hear from users. There is also a `geomview-users' mailing list for announcements regarding Geomview and for Geomview users to communicate with each other. If you use Geomview please send an email note to `geomview-users-request@geom.umn.edu' requesting to be added to this mailing list. File: geomview Node: Authors, Prev: What, Up: Top, Next: Register Authors ======= Tamara Munzner, Stuart Levy, and Mark Phillips are the original authors of Geomview. Celeste Fowler, Charlie Gunn, and Nathaniel Thurston also made significant contributions. Daniel Krech and Scott Wisdom did the NeXTStep and RenderMan port, and Daeron Meyer is currently working on a port to X windows. Mark Phillips wrote this manual, with substantial help from Stuart Levy and Tamara Munzner. Countless Geomview users have also been of great help by reading it and pointing out mistakes. File: geomview Node: Register, Prev: Authors, Up: Top, Next: Overview Let Us Hear From You ******************** We are very interested in hearing about how you are using Geomview. Think of Geometry Center software as a new kind of shareware: you share your science and successes with us, and we share our software and support with you. The Geometry Center is funded by the National Science Foundation, and it is important that we be able to report to NSF the ways in which our software is being used. If you use Geomview, please send us a letter telling us what you are doing with it. We need to know: 1. What you are working on - an abstract of your work would be fine. 2. How Geomview has helped you, for example, by increasing your productivity or allowing you to do things you could not do before. In particular, if you feel that Geomview has had a direct bearing on your work, please tell us about this. Please send the letter either via email to `register@geom.umn.edu', or via regular mail to the address below. Moreover, if you use Geomview or other Geometry Center software in your work, we encourage you to cite its use in your publications. Thank you! Software Development Group Geometry Center 1300 South 2nd St, Suite 500 Minneapolis, MN 55454 USA File: geomview Node: Overview, Prev: Register, Up: Top, Next: Tutorial Overview ******** Geomview's main purpose is to display objects whose geometry is given, allowing interactive control over details such as point of view, speed of movement, appearance of surfaces and lines, and so on. Geomview can handle any number of objects and allows both separate and collective control over them. The simplest way to use Geomview is as a standalone viewer to see and manipulate objects. It can display objects described in a variety of file formats. It comes with a wide variety of example objects, and you can create your own objects. You can also use Geomview to handle the display of data coming from another program that is running simultaneously. As the other program changes the data, the Geomview image reflects the changes. Programs that generate objects and use Geomview to display them are called *external modules*. External modules can control almost all aspects of Geomview. The idea here is that many aspects of the display and interaction parts of geometry software are independent of the geometric content and can be collected together in a single piece of software that can be used in a wide variety of situations. The author of the external module can then concentrate on implementing the desired algorithms and leave the display aspects to Geomview. Geomview comes with a collection of sample external modules, and this manual describes how to write your own. Geomview represents the current state of an ongoing effort at the Geometry Center to provide interactive geometry software that is particularly appropriate for mathematics research and education. In particular, Geomview can display things in hyperbolic and spherical space as well as Euclidean space. Geomview allows multiple independently controllable objects and cameras. It provides interactive control for motion, appearances (including lighting, shading, and materials), picking on an object, edge or vertex level, snapshots in SGI image file or Renderman RIB format, and adding or deleting objects is provided through direct mouse manipulation, control panels, and keyboard shortcuts. Geomview supports the following simple data types: polyhedra with shared vertices (.off), quadrilaterals, rectangular meshes, vectors, and Bezier surface patches of arbitrary degree including rational patches. Object hierarchies can be constructed with lists of objects and instances of object(s) transformed by one or many 4x4 matrices. Arbitrary portions of changing hierarchies may be transmitted by creating named references. Geomview can display Mathematica graphics output. File: geomview Node: Tutorial, Prev: Overview, Up: Top, Next: Interaction Tutorial ******** This chapter leads you through some of the basics of using Geomview. Work through this chapter in front of a workstation where you can try out the examples given here to get a feel for what you can do with Geomview. To start Geomview, login to the computer and get a shell window. A shell window is a window in which you can type unix commands; the prompt in the window usually ends with a '%'. In the shell window (the mouse cursor must be in the window) type the following (`RET' here means hit the "Enter" key): geomview tetra dodec RET This command starts up Geomview and loads two example objects, a tetrahedron and a dodecahedron. After a few seconds three windows should appear as shown in Figure 1. (The figures in this document appear only in the hardcopy version, not the Info version.) The panel on the left is Geomview's main control panel; it's called the *Main* panel. The skinny panel in the middle is the *Tools* panel and is for selecting different kinds of motions. The window on the right is the camera window and in it you see a large tetrahedron and a dodecahedron which is partially obscured by the tetrahedron. Geomview has lots of panels but by default it displays only these three. We'll describe some aspects of these and a couple of the others in this tutorial. You can read more about these and other panels in the later chapters of this manual. Put the mouse cursor in the camera window and press down and hold the left mouse button. Now, while holding down the button, slowly move the mouse around. You should see the picture rotate in the direction you move the mouse. If you lift up on the mouse button while moving the mouse, the picture continues rotating. To stop it, hold the mouse very still and click down and up on the left mouse button. Geomview uses the *glass sphere* model for mouse-based motion. This means you are supposed to think of the object as being inside an invisible sphere and the mouse cursor is a gripper outside the sphere. When you hold down the left mouse button, the gripper grabs the sphere; when you let go of the button, the gripper releases the sphere. Moving the mouse while holding the button down causes the sphere (and hence the object) to move in the same direction as the mouse. In addition to the two solids you should also see two wireframe boxes in the camera window. These are the "bounding boxes" of the two objects. By default Geomview puts a bounding box around each object that it displays so that you have an idea of how large it is. Notice that as you move the mouse around the tetrahedron and dodecahedron move as a unit. That is because by default what you are actually moving is the "World". To move an individual object instead of the whole world, move the mouse cursor to the *TARGET* browser in the *Main* panel. Click (any button) on the word *tetra*. This makes the tetrahedron be the "target object". Now move the cursor back to the camera window and you can rotate just the tetrahedron. The motion that you have been applying up to now has been rotation, because that is the motion mode that is selected in the *Tools* panel. To translate instead, click on the *Translate* button. Now when you move the mouse in the camera window while holding down the left button, the tetrahedron (which should still be the target object from before) will translate in the direction you move the mouse. Notice that you can translate it beyond the edge of the window as long as you keep holding the left mouse button down. If you lift up on the mouse button while moving the mouse, the tetrahedron will keep going. It moves rather rapidly so it is very easy to lose track of where it is. If you accidentally lose the tetrahedron by translating it too far out of the view of the window, you can get it back by clicking on the *Center* button in the *Tools* panel. This causes it to come back to its initial position. Click on the *Center* button to bring the tetrahedron home, and then translate it off to one side so that you can completely see the dodecahedron. Your world now has two objects in it that are beside each other. You should see the dodecahedron in the middle of the window and maybe part of the tetrahedron off to one side. Go back to the *TARGET* browser in the *Main* panel and click on "World" to select the whole world again. Now click on the *Look At* button in the *Tools* panel. You should see something like Figure 2 --- the dodecahedron and the tetrahedron in the middle of the window next to each other. The *Look At* button positions the camera in such a way that the target object is centered in the window. Now put the cursor over the middle of the dodecahedron and double-click the right mouse button. This means click it down-and-up two times in rapid succession. Notice that the dodecahedron becomes the target object; you can see this in the *TARGET* browser in the *Main* panel. Double-clicking the right mouse button on an object is another way to make it the target object. Go to the *PANELS* browser in the *Main* panel and click on the word *Appearance*. This brings up the *Appearance* panel. When it appears, if it partially obscures another Geomview window you can move it off to one side by dragging its frame with the middle mouse button down. The *Appearance* panel lets you control various things about the way Geomview draws objects. In the upper right corner, under the *Done* button are buttons labeled *[af] Faces* and *[ae] Edges*. Click on the *[ae] Edges* one, and notice that Geomview is now drawing the edges of the dodecahedron. Click on it again and the edges go away. Click several times and watch the edges come and go. When you've had enough of this, leave the edges on and click the *[af] Faces* button. This toggles the faces on and off. Click the button again to turn them back on. Now click on the *[Cf] Faces* button under the word *COLOR*. A color chooser panel like the one in Figure 4 should appear. Put the cursor in the color hexagon in this panel and hold down the left mouse button. Slowly move the mouse around. This drags the little black point around to choose a new color for the dodecahedron. The previous colors were specified in the file `dodec' that you loaded when we started Geomview. The color that you specify with the color panel overrides the old colors. You can adjust the intensity of the color with the *Intensity* slider. When you find a color that you like, click the *OK* button. Now put the cursor somewhere over the gray background and double-click the right mouse button; this picks "World" as the target object. Click the *Look At* button to look at the world again. Notice that in the *Appearance* panel the settings of the buttons have changed from the way you left them with the dodecahedron. That's because the *Appearance* panel always displays the settings for the target object, which is now the world, which still has its default settings. Click on the *[ab] BBox* button under the word *Draw*. The bounding boxes go away. Now put the cursor back in the camera window. At the keyboard, type the keys `a b'. Notice that the bounding boxes come back. `a b' is the keyboard shortcut for the bounding box toggle button; the string "[ab]" appears on the button to indicate this. Most of Geomview's buttons have keyboard shortcuts that you can use instead if you want. This is useful once you are familiar with Geomview and don't want to have to move around among lots of panels. Now select the tetrahedron, either by double-clicking the right mouse button on it, or by selecting "tetra" in the *TARGET* browser. Then click on the *Delete* button in the *Main* panel. The tetrahedron should disappear. This is how you get rid of an object. You can also load objects from within Geomview. Click on the *Load* button in the main panel. The *Files* panel will appear. Near the top of this panel is a browser with three lines in it; the second line is a directory with lots of Geomview example files in it. Click on that second line. Your *Files* panel should then look something like Figure 5. Scroll down in the list of files until you see `tref.off'. Click on that line, and then click on the *Add* button. A large trefoil-shaped tube will appear in your window. Click the *Done* button in the *Files* panel to dismiss the panel. Now click on the *Reset* button in the *Tools* panel. This causes everything to return to its home position. You should see something like Figure 6 at this point: a dodecahedron and a trefoil knot. Play around with the trefoil knot and the dodecahedron. Experiment with some of the other buttons in the *Tools* panel. Try coloring the trefoil knot with the *Appearance* panel. For a tutorial on how to create your own objects to load into Geomview, see file `doc/oogltour' distributed with Geomview (`/u/gcg/ngrap/doc/oogltour' on the Geometry Center system). The things in that file will be incorporated into a future version of this manual. File: geomview Node: Interaction, Prev: Tutorial, Up: Top, Next: Starting Geomview Interaction *********** This chapter describes how you interact with Geomview through the mouse and keyboard. * Menu: * Starting Geomview:: Starting Geomview. * Command Line Options:: Command Line Options. * Basic Interaction:: Basic Interaction: The Main Panel. * Loading:: Loading Objects Into Geomview. * Mouse Motions:: Using the Mouse to Manipulate Objects. * Appearance:: Changing the Way Things Look. * Cameras:: Cameras. * Saving:: Saving your work. * Command Obscure:: The Commands and Obscure Panels. * Keyboard Shortcuts:: Keyboard Shortcuts. File: geomview Node: Starting Geomview, Prev: Interaction, Up: Interaction, Next: Command Line Options Starting Geomview ================= The usual way to start Geomview is to type `geomview RET' in a shell window (RET means hit the "Enter" key). It may take Geomview a few seconds to start up; one or more windows will appear and you can begin interacting with Geomview immediately. It is also possible to specify actions for Geomview to perform at startup time by giving arguments in the shell command line. *Note Command Line Options::. File: geomview Node: Command Line Options, Prev: Starting Geomview, Up: Interaction, Next: Basic Interaction Command Line Options ==================== Here are the command line options that Geomview allows: `-b R G B' Set the window background color to the given R G B values. `-c FILE' Interpret the gcl commands in FILE, which may be the special symbol `-' for standard input. For a description of gcl, *Note GCL::. `-c COMMAND' Commands may also be supplied literally, as in -c "(ui-panel main off)" Since COMMAND includes parentheses, which have special meaning to the shell, COMMAND must be quoted. `-wins NWINS' Causes Geomview to initially display NWINS camera windows. `-wpos WIDTH,HEIGHT[@XMIN,YMIN]' Specifies the initial location and size of the first camera window. The values for WIDTH, HEIGHT, XMIN, and YMIN are in screen (pixel) coordinates. `-wpos -' You are prompted for placement of the first camera window. `-M OBJECTNAME' Display (possibly dynamically changing) geometry sent from the `geomstuff' program. This actually listens to the named pipe `/tmp/geomview/objectname'; you can achieve the same effect with the shell commands: mkdir /tmp/geomview mknod /tmp/geomview/objectname p (assuming the directory and named pipe don't already exist), then executing the gcl command: `(geometry objectname < /tmp/geomview/objectname)' `-Mc PIPENAME' Like `-M' above, but expects gcl commands, rather than OOGL geometry data, on the connection. `-nopanels' Start up displaying no panels, only graphics windows. Panels may be invoked later as usual with the `Px' keyboard shortcuts or with the `ui-panel' command. `-e MODULE' Start an external module; MODULE is the name associated with the module, appearing in the main panel's Applications browser, as defined by the `emodule-define' command. `-start MODULE ARGS ...' Like -e but allows you to pass arguments to the external module. "--" signals the end of the argument list; the "--" may be omitted if it would be the last argument on the Geomview command line. `-run SHELL-COMMAND ARGS ...' Like -start but takes the pathname of executable of the external module instead of the module's name. File: geomview Node: Basic Interaction, Prev: Command Line Options, Up: Interaction, Next: Loading Basic Interaction: The Main Panel ================================= Normally when you invoke Geomview, three windows appear: the *Main* panel, the *Tools* panel, and one camera window. Geomview has many other windows but most things can be done with these three and so by default the others do not appear. This section of the manual introduces some basic concepts that are used throughout the rest of the manual and describes the *Main* panel. Geomview can display an arbitrary number of objects simultaneously. The *TARGET* browser in the *Main* panel displays a list of all the objects that Geomview currently knows about. This browser has a line for each object that you have loaded, plus some lines for other objects. One of the other objects is called `World' and corresponds to the all the currently loaded objects, treated as if they were one object. Most of the operations that you can do to one object, such as applying a motion or changing a color, can also be done to the "World" object. The *TARGET* browser also has an entry for each camera. By default there is only one camera; it is possible to add more of them via the *Camera* panel. Geomview treats cameras in much the same way as it does geometric objects. For example, you can move cameras around and add them and delete them just as with geometric objects. Cameras do not usually show up in the display as an object that you see. Each camera has a separate camera window which displays the view as seen by that camera. (It is possible for each camera to display a geometric representation of other cameras; *Note Cameras::.) Because Geomview treats cameras and geometric objects very similarly, the term "object" in this documentation is used to refer to either one. When we need to distinguish between the two kinds of objects, we use the term "geom" to denote a geometric object and the word "camera" to denote a camera. The object which is selected (highlighted) in the *TARGET* browser is called the "target" object. This is the object that receives any actions that you do with the mouse or keyboard. You can change the target object by selecting a different line in the *TARGET* browser. Another way to change the target object is to put the mouse cursor directly over a geom in a camera window and rapidly double-click the right mouse button. This process is called "picking"; the picked object becomes the new target. Geomview objects are all known by two names, both of which are shown in the *TARGET* browser. The first name given there, which appears in square brackets ([ ]), is a short name assigned by Geomview when you load the object. It consists of the letter `g' for geoms and `c' for cameras, followed by a number. The second name is a longer more descriptive name; by default this is the name of the file that the object was loaded from. The two names are equivalent as far as Geomview is concerned; at any point where you need to specify a name you can give either one. To manipulate an object, make sure you that the object you want to move is the target object, and put the mouse cursor in a camera window. Motions are applied by holding down either the left or middle mouse button and moving the mouse. There are several different motion "modes", each for applying a different kind of motion. The *MOTION MODE* browser in the *Main* panel indicates the current motion mode. The default is "Rotate". You can change the current motion mode by selecting a new one in the *MOTION MODE* browser, or by using the *Tools* panel. For more information about motion modes, *Note Mouse Motions::. The *Load* button on the *Main* panel brings up the *Files* panel for loading a file. The file can contain either a geom, a camera, or gcl commands. For details, *Note Loading::. The *Delete* button causes the target object to be deleted. Geomview selects another object to be the new target. You can delete cameras as well as geoms in this way. If you hit the *Delete* button while the target object is "World", Geomview deletes all geoms. The *Panels* browser on the *Main* panel lists all the Geomview panels. Click on a panel's entry to bring that panel up. The *Modules* browser lists Geomview external modules. An external module is a separate program that interacts with Geomview to extend its functionality. For information on external modules, *Note Modules::. The three buttons at the bottom of the *Main* panel, labeled *Euclidean*, *Hyperbolic*, and *Spherical*, allow you to change the geometry of the space that Geomview displays. By default *Euclidean* is selected. For details about using *Hyperbolic* and *Spherical* spaces, *Note Non-Euclidean Geometry::. Most actions that you can do through Geomview's panels have equivalent keyboard shortcuts so that you can do the same action by typing a sequence of keys on the keyboard. This is useful for advanced users who are familiar with Geomview's capabilities and want to work quickly without having to have lots of panels cluttering up the screen. Keyboard shortcuts are usually indicated in square brackets ([ ]) near the corresponding item in a panel. For example, the keyboard shortcut for *Rotate* mode is 'r'; this is indicated by "[r]" appearing before the word "Rotate" in the *MOTION MODE* browser. To use this keyboard shortcut, just hit the `r' key while the mouse cursor is in any Geomview window. Do not hit the `RET' key afterwards. Some keyboard shortcuts consist of more than one key. In these cases just type the keys one after the other, with no `RET' afterwards. Keyboard shortcuts are case sensitive. The *keyboard* field in the upper left corner of the *Main* panel echos the current state of keyboard shortcuts. The button labeled *?* near the top right corner of the *Main* panel causes Geomview to print out a list of all keyboard shortcuts to standard output. The *Quit* button on the main panel terminates Geomview. File: geomview Node: Loading, Prev: Basic Interaction, Up: Interaction, Next: Mouse Motions Loading Objects Into Geomview ============================= There are several ways to load an object into Geomview. the *Files* panel If you click the *Load* button in Geomview's *Main* panel, the *Files* panel will appear. This panel lets you select a file from a variety of directories. The short browser at the top of the panel shows the selected directory, and the longer browser beneath it shows the files in that directory. To select a file, click on it. After a file is selected, you can load it into Geomview by clicking either the *Add* or *Replace* button. The *Add* button causes Geomview to load the file as a new object; a new entry will appear in the *Objects* browser in the *Main* panel, and all objects currently loaded will remain unchanged. The *Replace* button causes Geomview to replace the current object with the object in the selected file. If the current object is the *World*, Geomview deletes all objects and loads the one in the file as a new object. If the current object is a camera, the *Replace* button has no effect. If the file that you select contains gcl commands rather than an OOGL object, the *Add* and *Replace* buttons both cause Geomview to interpret the commands in the file. For more information about this, *Note GCL::. When the *Files* panel first appears, the directory selected in the directory browser is the current directory --- the one from which you invoked Geomview. The file browser shows *all* the files in this directory, including ones that are not Geomview files. If you try to load a file that doesn't contain either an OOGL object or Geomview commands, Geomview will print out an error message. The directory browser also lists a second and third directory in addition to the current directory. The second one, which ends in `data/geom', is the Geomview example data directory. This contains a wide variety of sample objects. It also contains several subdirectories. In particular, the `hyperbolic' and `spherical' subdirectories have sample hyperbolic and spherical objects, respectively. Directory entries in the browser look just like file entries; to view a subdirectory, click on it. The third directory shown in the directory browser, which ends in `geom', contains several subdirectories with other Geomview files in them. These are used less frequently than the ones in the `data/geom' directory. You can change the list of directories shown the *Files* panel's directory browser by using the `set-load-path' command; *Note GCL::. the `<' keyboard shortcut: If you type `<' in any Geomview window, the *Load* panel will appear. This is a small version of the *Files* panel; it contains a text field in which you can enter the name of a file to load. After typing the name of the file to load, type `RET'; Geomview will load the file as if you had loaded it with the *Add* button in the *Files* panel. If, after bringing up the small load panel with `<', you decide you want to use the larger *Files* panel after all, press the *Files Browser* button. geometry loading commands: The `load', `geometry', `new-geometry', and `read' gcl commands allow you to load an object into Geomview; *Note GCL::. File: geomview Node: Mouse Motions, Prev: Loading, Up: Interaction, Next: Point of Interest Using the Mouse to Manipulate Objects ===================================== Geomview lets you manipulate objects with the mouse. There are six different mouse motion modes: *Rotate*, *Translate*, *Cam Fly*, *Cam Zoom*, *Geom Scale*, and *Cam Orbit*. The tools panel has a button for each of these modes; to switch modes, click on the corresponding button. You can also select these through the *Motion Mode* browser on the *Main* panel. This section describes basic mouse interaction. There are some more advanced features available on the *Obscure* panel. For details, *Note Command Obscure::. Each of the motion modes uses a common paradigm for how the motion is applied. In particular, each depends on the current *target* object and the current *center* object. These are explained in the following paragraphs. The current target object is shown in the *Target* field in the *Tools* panel. This is the same as the selected object in the *TARGET OBJECTS* browser in the *Main* panel, and you can change it by either selecting a new object in the browser, by typing a new entry in the field, or by picking an object in a camera window by double-clicking the right mouse button with the cursor over the object. The current center object is shown in the *Center* field in the *Tools* panel. Its default value is the special word "target", which means that the center object is whatever the target object is. You can change the center to any object by typing it in the *Center* field. The origin of the center object is held fixed in *Rotate* and *Orbit* modes. Normally the center object is one of the existing geoms listed in the *TARGET OBJECTS* browser, and the actual center of rotations is the origin of that object's coordinate system. It is possible, however, to select an arbitrary point of interest on an object as the center. For details, *Note Point of Interest::. You apply a mouse motion by holding down either the left or middle mouse button with the cursor in a camera window and moving the mouse. Most of the modes have *inertia*, which means that if you let go of the button while moving the mouse, the motion will continue. It may be helpful to imagine the mouse cursor as being a gripper; when you hold a mouse button down, it grips the target object and you can move it. When you let go of the mouse button, the gripper releases the object. Letting go of the mouse button while moving the mouse is like throwing the object --- the object continues moving independent of the mouse. Inertia can be turned off; see the button on the *Obscure* panel. Most of the mouse motions have a slow motion version which you get by holding down the shift key while doing the motion as usual. This is useful for finer control. You can pick any point on an object (not just its origin) as the center of motion by holding down the shift key while clicking the right mouse button; this chooses a point of interest. *Rotate* In *Rotate* mode, hold the left mouse button down to rotate the target object about the center object. Rotation proceeds in the direction that you move the mouse. Specifically, the axis of rotation passes through the origin of the center object, is parallel to the camera view plane, and is perpendicular to the direction of motion of the mouse. When the center is "target", this means that the target object rotates about its own origin. The middle mouse button in *Rotate* mode rotates the target object about an axis perpendicular to the view plane. *Translate* In *Translate* mode, hold the left mouse button down to translate the target object in the direction of mouse motion. The middle mouse button translates the target along an axis perpendicular to the view plane. In Euclidean space, the center object is essentially irrelevant for translations. In hyperbolic and spherical spaces, where translations have a unique axis, this axis is chosen to go through the origin of the center object. *Cam Fly* *Cam Fly* is a crude flight simulator that lets you fly around the scene. It works by moving the camera. Move the mouse while holding the left mouse button down to point the camera in a different direction. To move forward or backward, hold down the middle button and move the mouse vertically. Both of these motions have inertia; typically the easiest way to fly around a scene is to give the camera a slight forward push by letting go of the middle button while moving the mouse upward, and then using the left button to steer. *Cam Fly* affects the camera window that the mouse is in; it ignores the target object and the center object. *Cam Orbit* *Cam Orbit* mode lets you rotate the current camera around the current center. The left mouse button does this rotation. The middle mouse button in *Cam Orbit* mode is the same as it is in *Cam Fly* mode: it moves the camera forward or backward. In general *Cam Orbit* does not move the target object, although if the current camera is selected as the target and the center is also the target, it will rotate that camera about itself just as in *Cam Fly* mode. *Cam Zoom* *Cam Zoom* mode lets you change the current camera's field of view with the mouse; hold the left mouse button down and move the mouse to change it. The numeric value of the field of view is shown in the *FOV* field in the *Camera* panel. *Geom Scale* *Geom Scale* mode lets you enlarge or shrink a geom. It operates on the target object if that object is a geom. If the target is a camera, *Geom Scale* operates on the geom that was most recently the target object. Moving the mouse while holding down the left mouse button scales the object either up or down, depending on the direction of mouse motion. The center of the applied scaling transformation is the center object. Scaling is meaningful only in Euclidean space; attempts to scale are ignored in other spaces. *Geom Scale* mode does not have inertia. The *Stop*, *Look At*, *Center*, and *Reset* buttons on the *Tools* panel perform actions related to motions but do not change the current motion mode. *Stop* The *Stop* button causes all motions to stop. It affects all moving objects; not just the target object. It's keyboard shortcut is `H'. The keyboard command `h', which does not correspond to a panel button, stops the current motion for the target object only. *Look At* The *Look At* button causes the current camera to be moved to a position such that it is looking at the target object, and such that the target object more or less fills the window. The Look At command is unreliable in non-Euclidean spaces. *Center* The *Center* button undoes the target object's transformation, moving it back to its home position, which is where it was when you originally loaded it into Geomview. *Reset* The *Reset* button stops all motion and causes all objects to move back to their home positions. The other four buttons on the *Tools* panel are: *MAIN* This button brings up the *Main* panel in case you have dismissed it or in case it is buried underneath other panels. *Done* This button dismisses the *Tools* panel. You can bring the panel back by selecting it in the *More Panels* browser in the *Main* panel, or via the `P t' keyboard shortcut. *Load* This is the same as the *Load* button on the *Main* panel; it brings up the *Files* panel. *Save* This is the same as the *Save* button on the *Main* panel; it brings up the *Save* panel. File: geomview Node: Point of Interest, Prev: Mouse Motions, Up: Mouse Motions, Next: Appearance Selecting a Point of Interest ----------------------------- It is sometimes useful to specify a particular point on some object in a geomview window as the center point for mouse motions. You can do this by shift-clicking the right mouse button (i.e. click it once while holding down the shift key on the keyboard) with the cursor over the desired point. This point then becomes the *point of interest*. The point of interest must be on an existing object. Selecting a point of interest simplifies examining a small portion of a larger object. Shift-right-click on an interesting point, and select *Orbit* mode. Use the middle mouse button to approach, and the left mouse to orbit the point, examining the region from different directions. When you have selected a point of interest, the current center object changes to an object named "CENTER", which is an invisible object located at the point of interest. In addition, mouse motions for the window in which you made the selection are adjusted so that the point of interest follows the mouse. You can change the point of interest at any time by selecting a new one by shift-clicking the right mouse button again. You can cancel the point of interest altogether by shift-clicking the right mouse button with the cursor on the background (i.e. not on any object). This changes the center object back to its default value, "target". The object named "CENTER", which serves as the center object for the point of interest, is a special kind of geom called an "alien". It does not appear in the *TARGET OBJECTS* browser. By default it has no geometry associated with it and hence is invisible. You can, however, explicitly give it some geometry using a GCL command, causing it to appear. Use the `geometry' command for this: `(geometry CENTER GEOMETRY)', where GEOMETRY is any valid geometry. For example, `(geometry CENTER { < xyz.vect })' causes the file `xyz.vect', which is one of the standard example files distributed with geomview, to be used at the geometry for CENTER. What actually happens internally when you select a point of interest is that the center is set to the object called CENTER, and that object is positioned at the point of interest. In addition, in order for mouse motions to track the point of interest, the current camera's focal length is set to be the distance from the camera to the point of interest. You can accomplish this via GCL with the following commands: (if (real-id CENTER) nil (new-alien CENTER {})) (ui-center CENTER) (transform-set CENTER universe universe translate X Y Z) (merge camera CAM-ID { focus D }) where `(X,Y,Z)' are the (universe) coordinates of the point of interest, and D is the distance from that point to the current camera, CAM-ID. The first command above creates the "alien" CENTER if it does not yet exist. File: geomview Node: Appearance, Prev: Point of Interest, Up: Interaction, Next: Appearance Panel Changing the Way Things Look ============================ Geomview uses a hierarchy of appearances to control the way things look. An "appearance" is a specification of information about how something should be drawn. This can include many things such things as color, lighting, material properties, and more. Appearances work in a hierarchal manner: if a certain appearance property, for example face color, is not specified in a particular object's appearance, that object is drawn using that property from the parent appearance. If both the parent and the child appearance specify a property, the child's setting takes precedence unless the parent appearance is set to override. Every geom in Geomview has an appearance associated with it. There is also an appearance associated with the "World" geom, which serves as the parent of each individual geom's appearance. Finally, there is an global "base" appearance, which is the parent of the World appearance. The base appearance specifies reasonable values for all appearance information, and by default none of the other appearances specify anything, which means they inherit their values from the base appearance. This means that by default all objects are drawn using the base appearance. If you change a certain appearance property for a geom, that property is used in drawing that geom. The parent appearance is used for any properties that you do not explicitly set. Geomview has three panels which let you modify appearances. * Menu: * Appearance Panel:: Color etc. * Materials Panel:: Surface Material properites. * Lighting Panel:: Lighting Parameters. File: geomview Node: Appearance Panel, Prev: Appearance, Up: Appearance, Next: Materials Panel The Appearance Panel -------------------- The *Appearance* panel lets you change most common appearance properties of the target object. If the target is an individual geom, then changes you make in the appearance panel apply to that geom's appearance. If the target is the World, then appearance panel changes apply to the World appearance *and* to all individual geom appearances. (Users have found that this is more desirable than having the changes only apply to the World appearance.) If the target is a camera, then appearance panel changes apply to the geom that was most recently the target. The five buttons near the upper right corner under the word *Draw* control what parts of the target geom are drawn. *Faces* This button specifies whether faces are drawn. *Edges* This button specifies whether edges are drawn. *BBox* This button specifies whether the bounding box is drawn. *Vects* This button specifies whether VECT objects are drawn. VECTs are a type of OOGL object that represent points and line segments in 3-space; they are distinct from edges of other kinds of objects, and it is sometimes desirable to have separate control over whether they are drawn. *Normals* This button specifies whether surface normal vectors are drawn. The four buttons under *COLOR* labeled *Faces*, *Edges*, *Normals*, and *BBox* let you specify the color of the corresponding aspect of the target geom. Clicking on one of them brings up a color chooser panel. The black dot in the center of the hexagon represents the current color; you can move it around by dragging it with the left mouse button down. The slider specifies the intensity. To accept the color that you have chosen, click the *OK* button. To cancel your color selection and return to the previous color, click the *Cancel* button. The *SHADING* browser lets you specify the shading model that Geomview uses to paint the target geom. *Constant* Every face of the object is drawn with a constant color which does not depend on the location of the face, the camera, or the light sources. If the object does not contain per-face or per-vertex colors, the diffuse color of the object's appearance is used. If the object contains per-face colors, they are used. If the object contains per-vertex colors, each face is painted using the color of its first vertex. *Flat* Each face of the object is drawn with a color that depends on the relative location of the face, the camera, and the light sources. The color is constant across the face but may change as the face, camera, or lights move. *Smooth* Each face of the object is drawn with smoothly interpolated colors based on the normal vectors at each vertex. If the object does not contain per-vertex normals, this has the same effect as flat shading. If the object has reasonable per-vertex normals, the effect is to smooth over the edges between the faces. *CSmooth* Each face of the object is drawn with exactly the specified color(s), independent of lighting, orientation, and material properties. If the object is defined with per-vertex colors, the colors are interpolated smoothly across the face; otherwise the effect is the same as in Constant shading style. The *Facing Normals* button on the *Appearance* panel indicates whether or not Geomview should arrange that normal vectors always face the viewer. If a normal vector points away from the viewer the color of the corresponding face or vertex usually is darker than is desired. Geomview can avoid this by using the opposite normal in shading calculations. This is the default. To change it so that the actual normals are used, press this button. This has no effect in constant shading mode. The three text fields in the lower left corner of the *Appearance* panel are: *Line Width* The width, in pixels, for lines drawn by Geomview. *Normal Length* This is actually a scale factor; when normal vectors are drawn, Geomview draws them to have a length that is their natural length times this number. *Patch Dicing* Geomview draws Bezier patches by first converting them to meshes. This parameter specifies the resolution of the mesh: if *Patch Dicing* is N, then an N by N mesh is used to draw each Bezier patch. if *Patch Dicing* is 1, the resolution reverts to a built-in default value. The *Revert* button on the *Appearance* panel undoes all settings in the target appearance. This causes the target geom to inherit all its appearance properties from its parent. The *Appearance* panel's *Override* button determines whether appearance controls should override settings in the objects themselves -- for example, setting the face color will affect all faces of objects with multi-colored facets. Otherwise, appearance controls only provide settings which the objects themselves do not specify. By default, *Override* is enabled. This button applies to all objects, and to all appearance-related panels. File: geomview Node: Materials Panel, Prev: Appearance Panel, Up: Appearance, Next: Lighting Panel The Materials Panel ------------------- The *Materials* panel controls material properties of surfaces. It works with the target object in the same way that the *Appearance* panel does. *Transparent* This button determines whether transparency is enabled. Geomview does not fully support transparency yet and on some machines it does not work at all. *Alpha* This slider determines the opacity/transparency when transparency is enabled. 0 means totally transparent, 1 means totally opaque. *Diffuse Reflectance* This slider controls the diffuse reflectance of a surface. This has to do with how much the surface scatters light that it reflects. *Shininess* This slider controls how shiny a surface is. This determines the size of specular highlights on the surface. Lower values give the surface a duller appearance. *Ambient Reflectance* This slider controls how much of the ambient light a surface reflects. *Specular Reflectance* This slider controls the specular reflectance of a surface. This has to do with how directly the surface reflects light rays. Higher values give brighter specular highlights. *Done* This button dismisses the *Materials* panel. File: geomview Node: Lighting Panel, Prev: Materials Panel, Up: Appearance, Next: Cameras The Lighting Panel ------------------ The *Lighting* panel controls the number, position, and color of the light sources used in shading. The *Lighting* panel is different from the *Appearance* and *Material* panels in that it always works with the base appearance. This is because it usually makes sense to use the same set of lights for drawing all objects in your scene. *LIGHTS* The *LIGHTS* browser shows the currently selected light. Changes made using the other widgets on this panel apply to this light. There is always at least one light, the ambient light. *Intensity* This slider controls the intensity of the current light. *Color* This button brings up a color chooser which lets you select the color of the current light. *Add* This button adds a light. *Delete* This button deletes the current light. *Show Lights* This button lets you see and change the positions of the light sources in a camera window. Each light is drawn as long cylinder which is supposed to remind you of a light beam. When you click on the *Show Lights* button Geomview goes into "light edit" mode, during which you can rotate current light by holding down the left mouse button and moving the mouse. Lights placed in this way are infinitely distant, so what you are changing is the angular position. Click on the *Show Lights* button again to return to the previous motion mode and to quit drawing the light beams. *Done* This button dismisses the *Lighting* panel. Geomview's *Appearance*, *Materials*, and *Lighting* panels are constructed to allow you to easily do most of the appearance related things that you might want to do. The appearance hierarchy that Geomview supports internally, however, is very complex and there are certain operations that you cannot do with the panels. The Geomview command language (gcl) provides complete support for appearance operations. In particular, the `merge-baseap' command can be used to change the base appearance (which, except for lighting, cannot be changed by Geomview's panels). The `merge-ap' command can be used to change an individual geom's appearance. Appearances can also be specified in OOGL files; for details, *Note Appearances::.