vtkOpenGLPolyDataMapper Edge Artifacts
While upgrading to VTK 9.0, we've found a number of situations where there is now significant artifacting on grid edges which was not present in VTK 8.2. We have tested with both the 9.0 release + "New surface with edges" patched in (!6880 (merged)), as well as the master branch, and both show this issue.
On light backgrounds, the triangulation is showing, particularly for line widths in the 1.0->3.0 range. None of the diagonal lines should be showing in this picture:
When we add extra conditions to the visibility mask in the mapper to selectively turn off certain edges (modifying vtkOpenGLIndexBufferObject, Line 90), the lines which should be masked out also bleed through with light backgrounds:
When the line widths are increased to the 4.0->6.0 range, the bleeds are much less noticeable, but the thin vertical artifacts on the right side of this image are introduced. There are also triangular artifacts along the top and bottom edges of the light blue square.
When rendering surfaces with edges, the edges are now much thicker than they were in 8.2, or currently are in wireframe only mode. This can crowd out the faces. It is also disorienting for users when they can easily switch between wireframe only and surface+edges modes. It appears that the extra width to the edges, while always thicker than in wireframe, may be partially dependent on either the absolute size of the grid, or size of grid cells. This makes it hard to get a more consistent look with different grids, which was possible with VTK 8.2.
Note: While possibly unrelated, the 9.0 upgrade has required noticeable changes to coincident topology offsets similar to #17936.