Multimedia Toolkit 2/Multimedia Toolkit 2.iso/imagine/imaginetutorial/brushmap.tutorial.pp/brushmap.tutorial

Text File | 1991-09-07 | 20.3 KB | 424 lines

Brush Maps. Second in a series about adding personal touches to
your Imagine objects. I'm sure this is the one that is more useful,
since brush maps are inherently confusing.


-Steve


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Textures are not the only way to add detail to an object. A more direct,
less elegant, but more personallizable method is to use brush maps. Brush
maps are ways of taking standard Amiga pictures (sometimes called IFFs,
though pictures are a subset of the Interchange File Format) that can be
placed "by hand" on your object. In its easiest incarnation, you could brush
map a picture of your face onto a flat plane, put a frame (using wood
texture! ) around it, and you have a virtual art piece. In its most complex
incarnation, you could take a set of 40 256-level intensity maps saved as
IFF24s and tile them endlessly on a plane during a 40 frame anim, and have
the map pixel intensity create reflections and highlights from the flat
plane just like it was really an animated, wind-wave covered ocean.

Brush maps can give objects the same four characteristics that textures can-
surface color, reflection, transparency, and surface orientation. Going back
to the "my face in a frame" example, a color map is straightforward. A
reflection map will reflect the color and intensity of light corresponding
to the map- in other words, a black map would make the picture in the frame
reflect no light, a white map would make the picture a mirror, and a yellow
map would make only yellow light reflect. [The yellow example is not
strictly true.. the yellow-mirror would reflect green and red light, which
combine to make yellow]. Transparency (really filter) is similar. Black is
opaque, pure white is the clearest crystal, and yellow would let yellow
light though.  An example given by Rick Rodriguez in his manual is that a
filter map of your face applied to a plane would be like a stained-glass
window. You could have fun with that. Note that transparent objects have an
index of refraction, which is set in the attributes requester. See my
article, "The Art of Glass" for a much more detailed discussion on
transparency.

The last brush type is altitude, which is a bit more tricky. Here, the
IMAGINE MANUAL IS COMPLETELY WRONG! [Sorry, Rick!] The manual describes a
"displacement map", which is somewhat similar. An altitude map just tells
Imagine that light hitting the object's surface should be reflected,
refracted, and specularated (!) as if it hit a surface that had a certain
shape to it- the shape describedthe brushmap's intensity. If you mapped a
picture with lots of small fuzzy grey dots onto a sphere, you would get
reflections and light highlights as if the sphere had tiny pits in it like
an orange. NOTE! The altitude map does NOT change the real surface height of
your object at all. THIS is the difference between a displacement map and an
altitude map.

One option you should use if you're using transparency map is the "Full
Scale Value" in the brush requester. This allows you to tell Imagine how
transparent a pure white image should be. If you want pure white to be
COMPLETELY transparent (invisible) set this number to 255 (full scale).  If
you set the number lower, you get full white to become opaque to whatever
degree you wish. If you're making a stained glass window, you might want to
set the number to 200 so that people can SEE that there is "glass" even
where there is a clear pane.  Impulse's old default was 245, I think.

Any standard Amiga IFF can be used as a map. This includes all pictures
savedDeluxe Paint, the most common picture editing program on the Amiga. A
format of high color resolutions known as IFF24 saves three bytes of color
information per pixel and produces beautiful color reproduction. These
IFF24s can be producedthe ToasterPaint, Digi-view RGB saves (only 21 bits,
but it is saved as 24 for compatibility), The Art Department, and many other
graphics programs. The Art Department is the penultimate tool for
manipulating 24-bit (and other) images- it can scale, compost, and
manipulate 24-bit pictures painlessly, as long as you have RAM. [It is NOT a
drawing program, though] Whatever type of brush you use, remember that
Imagine can't do magic to your pictures- a 16 color picture of yourself is
going to look positively cheesy compared to a 24-bit picture. For some
applications, though, you don't need much more.  Applying a 4-color logo to
an object won't benefit by using a 16 million color brush - just use 4.
Also, higher resolution is obviously higher quality, though it's pointless
to use a 1000 by 1000 picture of a logo- even in a close-up shot, it would
be indistinguishable from a 640 by 400 picture. Too low a resolution, though
will be painfully obvious when you render. Depending on how close of a view
you use in Imagine, you usually don't need more than 320 by 200. Again, this
is very dependent on how close your camera view is. I've used 100 by 100
brushes to great effect.

A fun trick- Imagine can easily _OUTPUT_ IFF24s... you can use a previous
rendering as a brush map.

If you are truly interested in making high quality brush maps, you should
definately use IFF24s as brushes. If you have DCTV, you have a terrific
paintbox for editing pictures. Toasterpaint also works, but is not pleasant.
If you don't have either (like me!), you can use a trick that works
extremely well.  I take a picture to be edited (often grabbed with
Digiview!) and in Art Department size it to about 900 by 600 (this is very
RAM limited... grey images can get 3 times as large). Then I display the
picture in overscan dithered EHB, and save this image. Then I power up
Deluxe Paint, and edit the picture. EHB gives you loads of colors to deal
with, so you don't lose too much color resolution. [You do lose some!]
DPaint can take brushmaps of any size [RAM limited!], and editing them is
quite easy. With the very large scale, individual pixels don't matter much,
so I use large brushes and the airbrush especially. When you're done
editing, I save the picture, and use Art Department to resize the image back
to its original size. For 24 bit pictures of a size of about 128 by 128, the
quality is terrific! You can see some of the brushes I made posted to ab20
and hubcap (the sidewalk and latticework, and my latest brick wall).

Sources of hi-quality pictures are everywhere. Digi-view is your friend- it
can make 768 by 480 resolution 24-bit pix. Toaster camera frame grabs will
give you 24-bit pix at a resolution of 768 by 240.  A fun source of varying
quality images are GIFs. GIFs are a graphic picture format, most popular on
MS-DOG computers. There are THOUSANDS of pictures, most with 256 colors out
of 16 million.  You can find about 1000 with a nice index on the anonymous
FTP site wuarchive.wustl.edu.  I often take these pix and shrink them by 1/2
and save them as 24-bit IFFs- there's no color loss and the file size is
much smaller.

Once you have your map and know what you want to do with it, you have to
place it on your object. The placement determines the size and orientation
of the map, as well as how much of the object is influenced, and in the case
of altitude maps, how much surface light is distorted.

There are three basic types of wrap- a "flat" wrap (Flat X Flat Z), a
"sphere" wrap (Wrap X Wrap Z), and a "cylinder" wrap (Flat X, Wrap Z and
Wrap X, Flat Z). Flat will ignore any surface bumps and features and just
apply itself directly, much like a slide projector would project onto a
bumpy screen. A sphere wrap tries to encase the object in the brush, then
shrinkwrap the map onto all of the surface features of the object. The
cylinder wrap tries to follow contours in one direction, but ignore them in
another. Think of taking a piece of gift wrap, and bending it around so its
a hollow cylinder.  Then place the object in the center of this vertical
gift wrap cylinder and push IN (but not up or down!) to follow the object
contours.

Placing the maps is sometimes tricky. Mike Halvorson wrote a description
that was posted about 6 weeks ago, you can find it in the Imagine list
archives. Also, the green Impulse Winter 1991 bulletin had two very useful
diagrams. What I'm about to describe is not as simple and foolproof as just
looking at the 4 simple pictures they printed, due to the mere fact that
ASCII graphics suck. But I'll try!

FLAT "WRAPS"

  Flat wraps are the most common and certainly the most controllable of the
brush map types. Think of having a decal or poster that you want to stick
onto a wall. Flat wrapping will do just this. A good example is trying to
put a logo onto the side of a truck- an excellent example of where brush
maps shine.

First, you should obviously have your logo picture and truck designed and
ready. Now, to place the brush onto an object, you should probably use the
"Edit Axes" mode. This lets you move the axes with the same mouse and
keyboard commands that you normally use for objects... m for move, s for
scale, r for rotate, x,y,and z to toggle a direction.

A danger with editing brush axes is that you want to be in LOCAL mode,
especially when you are scaling the brush axis in just one direction (like
you were trying to increase its height, keeping the same width and depth.)
If you don't scale in LOCAL mode, sometimes your changes don't stick. You
can check by selecting "Edit Axes" again to make sure nothing changes after
you're done.


The axis you are editing has a bit yellow bounding box that is very
deceiving. THE AREA WHERE THE BRUSH IS ACTUALLY MAPPED IS JUST THE UPPER
RIGHT QUADRANT OF THIS BOX. The brush is placed with its lower left corner
right at the center of the axes, and its upper right corner at a point
definedthe X and Z axes of the brush map axis.  Got that?

            Z
 +----------^------------+     Front View
 |          |xxxxxxxxxxxx|
 |          |x Picture xx|
 |          |xx Area xxxx|
 |          |xxxxxxxxxxxx|
 |          +------------> X
 |                       |
 |                       |
 |                       |
 |                       | <-brush map bounding box
 +-----------------------+


You want to position the axes so that the upper-right quadrant lies exactly
where you want your brush to lie. If you want your brush to cover the entire
side of the truck, you'd probably want to make the brush a few extra pixels
high and wide so that you don't accidentally get a border around the edge of
your logo.

The Y axis of the brush map is pretty important as well. It tells Imagine
how DEEP to apply your brush. Basically, any part of the object that falls
between the axis origin and the tip of the Y axis WILL be colored (or
reflected, or whatever). For the truck, you'd want to move and scale the
brush axis in the Y direction so that the Y axis line INTERSECTS one side of
the truck but NOT the other. The intersected side of the truck would be
within the influence of the brush map, whereas the other side of the truck
would be left alone. If you scaled the Y axis to include both truck sides,
the other side of the truck would get the brush map applied to it as well.
[In fact, you'd see a mirror image of the brush on the other side, since
you'd be looking at it in the other direction.]

Here's a terrible ASCII drawing showing how you'd position a brush so that
it puts a very small logo on the side of a big rectangular solid, like a
truck body.

                 FRONT VIEW


        +-----------------------------------------+
        |                                         | <-Truck body
        |                                         |
        |                                         |
        |                  ^ X                    |
        |                  |                      |
        |        Brush     |                      |
        |        axis->    +-----> Z              |
        |                                         |
        |                                         |
        |                                         |
        |                                         |
        +-----------------------------------------+


===============================================================


                  TOP VIEW

        +-----------------------------------------+ <-Truck Body
        |                                         |
        |                                         |
        |                                         |
        |                                         |
        |                                         |
        |                  ^ Y                    |
        |                  |                      |
        +------------------+----------------------+
                           |
              Brush->      +-----> Z
               Axis



See how the Y axis only intersects one side?

That's about it for flat wrapping. It is pretty easy to control where
the brush gets applied to any object.


WRAP X WRAP Z  WRAPS

-----

These are the most complex wraps. The Y axis here isn't really used,
since the wrap is applied to the whole object surface, not just part.

You want to position the axes so that the Z axis covers the entire height of
the object... its height should be slightly TALLER than the object. The X
axis should be thought as a "radius of influence"... it should be a little
bit bigger than HALF the width of the object.  The axis should be placed
(LOOKING DOWN!!) at the center of the object, and looking from the side, at
the bottom of the object. The Z axis should pass through and be slightly
bigger than the object's height.  The X axis should be slightly bigger than
the object's maximum radius away from the center. The Y axis size doesn't
matter. Keep it small, suggests Impulse.


OK, Here's the diagram. The object is a sphere. I swear!

===========================================================
FRONT VIEW
                     ^ Z <- brush axis
                     |
                   __|__
                  /  |  \
                 -   |   -
                /    |    \
               /     |     \
              |      |      |
              |      |      |
              |      |      | <-Sphere-like object
              |      |      |
              \      |     /
               \     |    /
                -    |   -
                 \   |  /
                  ---+--
                     |
                     +--------> X


===========================================================
TOP VIEW
                   _____
                  /     \
                 -       -   <-Sphere-like object
                /         \
               /           \
              |      ^ Y    |
              |      |      |
              |      +------+-> X
              |             |   Brush Axes
              |             |
              \            /
               \          /
                -        -
                 \      /
                  ------



That's it! If you wrap a picture of a grid of lines, it will come
out looking like latitude and longitude lines on a globe.



CYLINDER WRAPS (WRAP X, FLAT Z, FLAT X, WRAP Z)

The brush placement is identical to the placement used for the spherical
wrap. The effect is quite different, however. If you tried cylinder wrapping
the grid picture onto a sphere, you'd get OK latitude lines (going
North-South) but the longitude lines would get further apart the closer you
were to the poles, due to the flat projection of the horizontal lines. The
lines themselves would also be wider at the poles.


One last note for brush axis placement- for adding ALTITUDE maps, the Y axis
depth is used to measure how much indentation a full scale range of
intensity (0-255) should simulate. For cylinder and sphere wraps, just scale
the Y axis. For orange pits, the axis might be 1% of the sphere's size. For
an eroded planet, you might use 10%. More than this would make really stupid
looking reflections. Altitude maps are subtle.

The Y depth is also used for flat altitude wraps, which might limit you if
you want to indent both sides of a truck. You'd have to use two brushes in
this case. I would have preferred a number gadget in the brush requester.

----------

Once you know how to place individual brushes, you can start with the fancy
tricks. Brushes overlay each other just like textures. You can put up to 4
brushes on an object, and they are applied in order. Many maps don't
interfere, though- you could have a color map and a reflection map on the
same object in the same place. Both will work just fine.

I am not positive, but I'm pretty sure brushes are put on AFTER
textures are applied. Otherwise you'd get wood grain on your face. :-)

Repeating brushmaps are a joy. They "tile" an object with an endless
succession of images both side to side and top to bottom. The brush will
repeat all the way out the the end of the object. If you tile a ground, the
brushes will go to infinity. The size of each tile is set by the brush axes,
just like a non-tiled map. The brushes are placed next to each other with no
space between them. You could draw a VERY detailed picture of a bathroom
tile, and map it onto a wall.  when rendered, the wall would be (surprise)
tiled! I've used this to GREAT effect for making very detailed sidewalks,
rose trellises, brick walls, roof shingles, and golf greens. All of these
are flat wraps. To be honest, I haven't tried infinite tiled wrap wraps...
I'm not sure what they'd do!

Placing repeating brushmaps is just the same as a regular flat wrap.  The
size of the brush is determinedthe X and Z axis, and the "depth of
influence" is determinedthe Y axis.

One additional option that is very useful is the "mirror" option. This makes
every tile be a mirror reflection of its neighbor. The great advantage of
this is that the edge colors ALWAYS match, just like if your finger touches
a mirror, your twin in the mirror will reach out and touch your finger at
the exact same place. This might hide discontinuities in your brushmap if
you want to hide the seams, or it might be a special effect you're looking
for.

Repeating brushmaps aren't just for covering an infinite plain with your
face. They can be an extremely powerful way to get very complex textures on
an object. You can imagine drawing one very high resolution, high quality
brick with scratches, pits, chips and tiny detail, then tiling it onto a
wall. Presto! You have a brick wall with a lot of character, unlike the
Brick texture which is too plain to fool anyone up close. This is probably
the most useful aspect of infinite tilings. You can find my infinite
sidewalk, infinite golf green, infinite brick wall (very nice!) and infinite
rose trellis on ab20 and hubcap.

When I refer to "ab20" and "hubcap" I mean the anonymous FTP sites
ab20.larc.nasa.gov and hubcap.clemson.edu, both of which have a lot of
Imagine files, objects, brush maps and goodies that I've uploaded.  There is
also an archive of this list on both sites. If you need to know if you have
FTP access and how to use it, ask one of your local computer experts- they
should be able to help you.

The last brush map ability is very useful. You can actually have ANIMATED
brush maps which change every frame.  Note that these pictures are not
"AnimBrushes" that DPaint will save. These are individual pictures, which
means you can have a 24 bit "animbrush."  To use this feature, you should
save the sequence of pictures you wish to show in a format like

  Mypic.0001
  Mypic.0002
  Mypic.0003
  Mypic.0004
  Mypic.0005

and so on up to however many pictures you have. Make sure to have FOUR
numbers in the extension. Mypic.01 will NOT work. To use this sequence of
pictures as an animation, you should use "Mypic" as the brush file name
[without the quotes], then set the "Max sequence #" to the number of
pictures you have. I wrote a LONG article about how you can make animations
of yourself using Digi-View and a VCR. You might have seen the animation
with me "trapped" inside of this giant sphere rolling around on a plane,
with my pitiful attempts to break out recorded in 16 glorious colors. You
too can do this with YOUR setup. It's worth playing with! You can find the
article in the Imagine archives on hubcap.

That's all there is to brush maps. They can add a lot of detail to your
objects, and they're not hard to use if you know how to place the axes. Go
out and create!



-Steve "Boy, are my fingers tired" Worley

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Steve Worley                                        [e-mail]
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