Cornell University Program of Computer Graphics
The material parameters which can be texture mapped
are specified as chunks.
Currently this applies to colors and the phong exponent.
Colors can be specified as either a color chunk or a texture chunk.
You cannot specify both a texture and color chunk.
Color chunks can be
spectral (spctrl), rgb (rgb), or scalar (sclr).
Other material modifiers (e.g. bump mapping)
would appear in the optional chunks at the end of a material.
Phong exponentsWhen texture mapping Phong exponents the following formula should be used:
e = 10^(0.0001*t^2)
where e is the Phong exponent and t is the 0-255 value from the texture map.
Inline versus named materialsThere are two different ways to make a diffuse red sphere. The first is to define the material inline:
sphr "white sphere" lmbrtn rgb 0.8 0.2 0.2 end end 0.0 0.0 0.0 1.0 % center,radius endThe other way is to define a material with a name and reference that name:
nmdMtrl "red" lmbrtn rgb 0.8 0.2 0.2 end end end sphr "white sphere" mtrlNm "red" end 0.0 0.0 0.0 1.0 % center, radius end
Using textures for material propertiesAnywhere a material specifies a color, a texture can be used in place of the color. You can think of a color as a texture map that always returns the same value. For example, to define a diffuse material whose reflectance is defined by a texture map in a ppm file:
lmbrtn imgFl "foo.ppm" "ppm" end endAlternatively, you could name the image and reference it:
nmdImg "foo" imgFl "foo.ppm" "ppm" end end lmbrtn imgNm "foo" end endFinally, you could define the pixels inline:
nmdImg "foo" imgDt 2 3 % a 2 by 3 image with rgbs rgbLst 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 end end end