GLSL shader example
Glowing Voronoi Cracks
Use the difference between the nearest two cell distances as an edge approximation; only near-equality boundaries emit light.
Live example
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What to observe
Glowing Voronoi Cracks.
Mechanism
Use the difference between the nearest two cell distances as an edge approximation; only near-equality boundaries emit light.
The controlling code
float d=cellEdge(p*4.);float glow=exp(-d*(12.+40.*u_parameter));c=vec3(.08+.07*noise(p*20.))+vec3(1.,.28,.05)*glow;
Experiment
Set the parameter to 0 and then 1 to change exp(-d*(12.+40.*u_parameter)) from a broad to a narrow glow. The cell boundaries stay in the same positions because their input remains p*4..
Debugging and cost
cellEdge checks a 3×3 neighborhood to approximate the gap between the two nearest seed distances. Change cellEdge(p*4.) to cellEdge(p*2.) to double the crack-cell size while keeping the same nine-neighbor search.