figure_skin

The single surface material every figure in "Standing Ovation" wears — the performer on the stage and all 1,412 members of the audience, who are the same man. One material is what keeps a 1,412-strong population one draw call per part, so everything that makes one of them a different man from the one in the next seat arrives through his own four vec4 instance lanes rather than through a material of his own.

lane0 carries (paintTint, grime, occupancy, seatId) and lane1 carries (mouthBoost, sweat, rise, clapPhase). The shader uses them to scale how heavily the greasepaint was laid on, to pull that paint toward the theatre's own green-grey bloom, to re-saturate the painted mouth — the only saturated colour in the film before Act IV — and to put a wet sheen over a working face. A lane nothing has written reads zero, which the shader reads as the sheet value rather than as a scrubbed face.

It is a surface() shader, so the engine lights it and the capture tool's albedo / roughness / normal passes answer about the material rather than about the final image. Greasepaint is a waxy layer over skin, so it forwards the subsurface lobe: uplight from fourteen footlights on a face that scattered none of it would read as a mask.