- missing vertical walls since a recent tessellator crash fix (fixes#17604)
- choice of the culling mode - no culling / back face / front face (fixes#17619)
- more unit tests for tessellator
As the readme of poly2tri library says: "Poly2Tri does not support repeat points within epsilon."
When the coordinates are very near to each other, we get crashes in triangulation code.
To prevent that, we try to simplify geometries to hopefully fix the problem automatically,
if that fails we just skip the polygon as the last resort.
Usually this happens if user tries to use 3D renderer on unprojected lat/lon coordinates.
Discovered by Nyall while working on PR #5708
Tessellation would shift coordinates because when points got reprojected
to the new base, the Z coordinates were considered zero (which worked only
when all points were on the same plane).
Previously the walls always had horizontal top/bottom, but
in vertex binding mode the walls need to have different z values
at the start and end coordinate
Note that the unit test exposes a different bug in the tesselator,
which should also be fixed...
