Remove inside (invisible) faces from a mesh.

[mgear]

this does something similar?

Mcs Caves & Overhangs [RELEASED]

The MCS Caves & Overhangs extension for MeshCombineStudio 2 is available on the Asset Store now. The best performance possible by using the easiest way to get amazing looking caves and overhangs on any terrain solution. The easiest way to create caves and overhangs (and best looking) is by placing rock models within Unity Editor (in conjunction with terrain). The issue is that it’s bad for performance because there’s a lot of rock geometry (triangles) that overlap with other rocks or are bel…

but if nothing else comes up, brute force check if face is inside mesh?

i’ve seen cad optimizers do hidden object removal with voxelized geometry checks… (easier to check if voxel is visible/accessible inside another)