#skinned-mesh

The practical patterns for Sandbox.Decal: orienting the projection box to a hit normal, keeping a decal byte-identical across multiplayer peers, making paint follow an animated character, and scaling to thousands of decals without a performance cliff, plus the pitfalls that catch each one.

A projected Sandbox.Decal seated on a character's analytic hit surface (e.g. a capsule hit position) with a shallow projection Depth paints the base skin mesh but ends before the clothing renderers' outer shell, so paint shows only where bare skin peeks out. Increase Depth to span the cloth shell without punching through thin limbs.

A world-space Sandbox.Decal is fixed in world space, so a splat spawned on a character projects onto empty air the instant they move. Parent the decal under the character, store the hit in a bone's local frame, and re-pin its world transform to that bone every frame so it re-projects onto the moving skinned mesh.