Color ΔE (CIE76)—lower = better skin/substrate match
Papillae / texture match—3D skin relief vs. substrate roughness
Camouflage effectiveness—from color + texture match
Predator detection risk—psychophysical contrast model
Substrate: rock
Predator: patrolling
Click a patch (sand / rock / coral) to move the octopus there.
Growing the reef floor…

Chromatophore gain sets how fast and how fully the skin's pigment cells expand toward the substrate color (first-order lag, τ ∝ 1/gain). Papillae amplitude sets the 3D muscular-hydrostat skin bumps that must match the substrate's own roughness. Both feed a real CIE76 color-distance + roughness-difference model that drives a predator's logistic detection probability — click a substrate patch to relocate the octopus and watch both readouts respond.