'parity': an odd number of crossings is inside (even-odd rule). Needs no
consistent winding; overlapping closed shells cancel where they overlap.
'winding': a non-zero sum of signed crossings is inside (non-zero rule;
+1 leaving through a triangle's authored front side, -1 entering through
it): the generalized winding number along the ray, an integer for closed
meshes. Overlapping closed shells stay inside; it needs consistently wound
triangles (either way round).
How the inside test reads one ray's crossings:
'parity': an odd number of crossings is inside (even-odd rule). Needs no consistent winding; overlapping closed shells cancel where they overlap.'winding': a non-zero sum of signed crossings is inside (non-zero rule; +1 leaving through a triangle's authored front side, -1 entering through it): the generalized winding number along the ray, an integer for closed meshes. Overlapping closed shells stay inside; it needs consistently wound triangles (either way round).