sssMask

Fills a marked mesh's silhouette with the scattering it was authored with: the tint in RGB, and in alpha the world-space distance light travels beneath the surface before it leaves, over [0, 1]. Alpha above zero is what marks a pixel as scattering at all, so a target cleared to zero reads as "no subsurface here".

A geometry pass draws through a material pipeline built for the frame's own colour format, which is why the mask is 8-bit rather than float. One group holds one radius, so that quantisation lands on the authored value rather than varying across a surface.

One material carries one group's values and sssDiffusion.renderFeature issues one draw per group, so meshes scattering differently keep their own numbers.

property	meaning
scatter_color	The tint, and per channel how far that channel travels.
scatter_radius	The distance light travels beneath the surface, in world units.