GLSL shader example
Noise Dissolve with a Burning Edge
One threshold keeps or removes a pixel; a second narrow interval adds the burning edge. Progress and edge width can be adjusted independently.
Live example
Edit the code and the preview updates as you type.
What to observe
Noise Dissolve with a Burning Edge.
Mechanism
One threshold keeps or removes a pixel; a second narrow interval adds the burning edge. Progress and edge width can be adjusted independently.
The controlling code
float n=fbm(uv*9.);float threshold=u_parameter;float mask=step(threshold,n),edge=(1.-smoothstep(threshold,threshold+.07,n))*mask;vec3 base=palette(uv.x+uv.y*.3);c=mix(c,base,mask)+vec3(1.,.28,.04)*edge;
Experiment
Change the fire-band upper edge threshold+.07 to threshold+.15. More surviving pixels near the threshold become orange, widening the hot boundary without changing which pixels the mask removes.
Debugging and cost
Both disappearance and fire edge share the same fbm(uv*9.), evaluated once. Temporarily set c=vec3(mask); before the final output to inspect the binary keep/remove decision separately from the edge's added brightness.