... using Select Box.
This is caused by our hack to make each triangle always output
at least 1 pixel. It stretches the triangle with a specific
winding order that is correct for any geometry even if it is
backfacing as long as it is subpixel. But if the mesh is
negatively scaled, the culling mode is flipped. Which make the
hardcoded offsets winding inverted, and then culled by the rasterizer
(or the fragment shader code).
The fix is to flip the winding order of the offsets depending on
the object matrix negativity.
This is rather expensive so we only do it for the triangles we know
are subpixels.
a29be9c5a2