nx_slice_plane_test.nx

nx_slice_plane_test.nx -- slice a unit tetrahedron at its midplane and verify the resulting segment soup describes the expected right-triangle cross-section. Tetrahedron at unit-mm scale: v0=(0,0,0), v1=(1,0,0), v2=(0,1,0), v3=(0,0,1) (in Q14: 0 vs 16384) Sliced at z = 0.5 mm (8192 Q14): T0 (v1,v2,v3): produces segment (8192,0) -- (0,8192) T1 (v0,v3,v2): produces segment (0,0) -- (0,8192) T2 (v0,v1,v3): produces segment (8192,0) -- (0,0) T3 (v0,v2,v1): all z=0, plane at 8192 -> all below -> no segment Result: 3 segments whose 6 endpoints cover the set {(0,0), (8192,0), (0,8192)}, each appearing exactly twice. This is the boundary of a right triangle in 2D. Closed-form invariants: (a) Soup verdict == OK. (b) Exactly 3 segments at z=8192. (c) Each of the 3 corner points appears exactly twice in the segment-endpoint multiset. (d) Slicing at z above tetrahedron (z = 2 * Q14) -> 0 segments. (e) Slicing at z below tetrahedron (z = -1) -> 0 segments. (f) Slicing at the bottom face (z = 0) yields 3 segments (the three coplanar tri edges of the bottom face's neighbours; T3 itself coplanar -> no segment). expect_exit: 0 license_tier: ORIGINAL