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On top of the framework I built for
Assignment 04 - RGS vs. BVH Bake-Off, I've
added the ability to set materials as solid textures. I did this by
creating a new class called a Channel whose sole function is to
provide a color output. So, for example, there is a class derived
from the channel called a ChannelColor, which is simply a
constant color. Derived from the Channel class is also a
ChannelMarble class which instantiates a Noise class to
compute octaves of noise and combines them into marble.
In the scene description file, you can now attach any color component
of a material (currently only ambient, diffuse and specular) to any of
these channels. It looks like this in the scene file:
material "red" {
diffuse { color < 1 0 0 > }
}
}
which will set the diffuse component to a constant red. Here's a more
complex example:
material "marble" {
diffuse {
marble {
scale 1
period 1.3
distortion 3
octaves 12
ramp {
< 1.0 0.000 0.0 >
< 1.0 0.125 0.0 >
< 1.0 0.250 0.0 >
< 1.0 0.375 0.0 >
< 1.0 0.500 0.0 >
< 1.0 0.625 0.0 >
< 1.0 0.750 0.0 >
< 1.0 0.875 0.0 >
}
}
}
}
which will set the diffuse channel to the marble function with the
given parameters.
The hope is that this organization will allow me the flexibility that
I want in setting up materials. Further work will include the ability
to combine several channels arithmetically, so I can get multi-pass
effects, or for things such as a base diffuse color modulated by a
marble procedure or an image (texture) map.
Here are some quick notes about how I generate the marble texture.
The function I use to compute the marble looks something like the
following:
abs( sin( 180 * ( period * v.x + distortion * Fractal3( v, octaves ) ) );
where v is the (possibly scaled) position at which the noise is
to be computed and Fractal3 is a fractal sum of noise computed
as follows:
float n = 0.0f;
for ( int i = 0; i < octaves; i++ )
{
float o = ( float )( 1 << i );
n += Noise3( v * o ) / o;
}
return n;
where Noise3 is the standard
Perlin Noise function.
Timings (MM:SS.S) are for 500x500 pixel images on a PentiumIII
733Mhz with 384MB SDRAM
(unless otherwise noted).
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