The RenderMan Interface - Paul Bourke

path of the ray.
The input Ci and Oi are the colors and opacities at the point P. The volume shader should
set the color and opacity that result at the point P-I.
16.4 Displacement Shaders
Displacement shaders move the position P of a surface. After a point of the surface is
moved, the normals should be recalculated with calculatenormal unless the new normals
can be computed as part of the displacement.
The following shader places a sinusoidal bump on a surface.
displacement
ripple( float amplitude = 1.0, float wavelength = 0.25 )
{
P += N * amplitude * sin( 2*PI*(s / wavelength) );
N = calculatenormal(P);
}
16.5 Imager Shaders
Imager shaders change the value of Ci and Oi. The exposure and quantization process
specified in the section on Displays in Part I could be specified as the following imager:
imager
exposure( float gain=1.0, gamma=1.0, one = 255, min = 0, max = 255 )
{
Ci = pow( gain * Ci, 1/gamma );
Ci = clamp( round( one * Ci ), min, max );
Oi = clamp( round( one * Oi ), min, max );
}
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