Depth testing was off as it used the precomputed ModelView matrix. As
draw engines currently use a different approach the depth was sometimes
a bit off making the color disappear.
This change will use a different vertex shader that will write the
correct depth. I expected the same change to be needed in the bone
selection overlay but was not able to reproduce it.
Reviewed By: fclem
Maniphest Tasks: T64615
Differential Revision: https://developer.blender.org/D5006
eeda9369b6