Black Line Problem

Usually it''s a sign of a T-junction, when some polygons don''t share all vertexes on a common edge.

Due to floating point inaccuracies, a dot (vertex) at 5.00000 could sometimes be 5.0000001 or 4.999999998. This causes the line to randomly appear and disappear.

The only way to fix it is to overlap the polygons a bit (but that can cause z fighting problems as a side effect)

What I personally do is turn off the "clear" command from wiping the screen. I always render out the entire screen anyways covering everything so the clear doesn''t matter. That way when this happens, the previous contents that where there hide the line and you don''t notice the line.

Actually, that''s not the case. If the two triangle''s edges shade the vertices the error accumulation is the same for both triangles, so eventhough they''re not rendered correctly, it still looks right (you don''t see the line because BOTH triangles are rendered with the same error).