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Tommaso Bianchi
695932ad87
A filleted solid arrived on the plate as a broken model: the slicer reported
"8 non-manifold edges" on an 80x50x12 box with r=3 on all edges, and advised
repairing it in another CAD application -- the exact round trip the Design tab
exists to remove. The same box without the fillet committed cleanly.
Measured rather than guessed. Each of the 8 bad edges is degenerate, both
endpoints the same vertex:
open tri=145 edge=1 face=5 v59(3.000000 3.000000 0.000000) v59(3.000000 3.000000 0.000000)
open tri=538 edge=1 face=6 v87(3.000000 3.000000 12.000000) v87(...)
... one per corner, 8 corners
OCCT triangulates a degenerate surface parameterization with a triangle at the
pole; a corner sphere patch has exactly one. Its two pole nodes are distinct in
the per-face triangulation and collapse to a single vertex when the faces are
welded, leaving a zero-area triangle whose v->v edge can never pair with a
neighbour. its_face_neighbors counts it as open, and the field the object panel
prints as "non-manifold edges" is in fact stats.open_edges.
So the geometry was never wrong -- the B-rep volume matches the Steiner formula
for a box dilated by a ball to 0.016%. Only the bookkeeping was.
Dropping those triangles after the weld removes 8 of 3492 and takes open_edges
to 0. Zero area, so nothing about the shape changes. tri_face is compacted in
the same pass, since it must stay index-aligned with the triangle list that the
face picking and per-body colouring both index into.
Guarded by a new [CadDocument] case that asserts open_edges == 0, no degenerate
triangle survives, and both per-triangle maps still match the triangle count.
The existing suite only ever checked B-rep volumes and areas, which is why a
mesh defect this visible went unnoticed: 150 cases / 2049 assertions green on
both forks.
snaporca-agw
OrcaSlicer tests
Building, running and writing tests is documented on the wiki, under How to Test.
Two files here rather than there, because coding agents only read what is in the repository: