Perlin Noise

//////////////////////////////////////////////////////////
// perlin-noise
// Concept: lattice-based gradient noise
// Use LATT to evaluate 2D Perlin noise across a field.
//
// https://en.wikipedia.org/wiki/Perlin_noise
//////////////////////////////////////////////////////////

// scale the input coordinate
&coord = mlt(C, 8);

// sample a rectangular lattice with quintic interpolation
// R provides random values and D provides local corner offsets
&perlin = LATT.RECT.QUINTIC[&coord]{
   dot(nrm(R), D)
};

#perlin {
   dim = (256,256,1);
   run = &perlin;
}

~perlin {
   // remap noise values from [-1, 1] to [0, 1]
   col = add(mlt(#perlin, 0.5), 0.5);
}