/usr/share/radiance/dirt.cal is in radiance-materials 4R1+20120125-1.1.
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1 2 3 4 5 6 7 8 9 10 | {
Dirt pattern.
This is probably the simplest application
imaginable for the fractal noise function.
A1 - degree of "dirtiness"; 1 is very dirty.
}
dirt = 1 - A1*.5*(1+fnoise3(Px,Py,Pz));
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