Possible loss of precision
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
I might have discovered a possible bug in VTK. The attached file gives a simple test where squares of decreasing size are placed in front of each other, so that smaller squares are in front of larger ones. Squares are sized by factors of 2, and there are 31 of them, so the smallest one has size of about 1e-9 of the largest one, and cannot be described by single precision coordinates. I use vtkPoints(VTK_DOUBLE) to insure that all coordinates are in double precision. Nevertheless, as you can see by running the test, the artifacts appear when the camera zooms to squares that are about 1e-7 of the largest ones, as if the coordinates are kept in floats despite being requested as doubles.
I am not 100% sure it is a bug in VTK, but I did try this test on two different video cards, one NVIDIA (under Linux) and another ATI (under Windows), to reduce a chance that the bug is in the OpenGL implementation.
The same behaviour appears under VTK 4.4.2 and 5.0.0.