Build the OPAQUE BASE cross-section for every MULTI-material entity — its
full solid section, ignoring the per-layer colour split.
Combining all of one entity's cut segments drops the (open) interface
boundaries and leaves only the wall's outer skin, which — because #1311 made
the union of layer bands watertight — is a set of CLOSED rings (the solid
chunks, with openings as holes/separate rings). So this needs no interface
stitching: the ordinary closed-loop builder resolves it robustly. Drawn
behind the per-layer fills in the 3D overlay, it guarantees a cut never reads
hollow even where the per-layer reconstruction has to fall back. Single-
material entities are skipped — their normal cutPolygons already fill solid.
Build the OPAQUE BASE cross-section for every MULTI-material entity — its full solid section, ignoring the per-layer colour split.
Combining all of one entity's cut segments drops the (open) interface boundaries and leaves only the wall's outer skin, which — because #1311 made the union of layer bands watertight — is a set of CLOSED rings (the solid chunks, with openings as holes/separate rings). So this needs no interface stitching: the ordinary closed-loop builder resolves it robustly. Drawn behind the per-layer fills in the 3D overlay, it guarantees a cut never reads hollow even where the per-layer reconstruction has to fall back. Single- material entities are skipped — their normal
cutPolygonsalready fill solid.