When using Vertex or Weight paint mode on a wireframe the overlay was
blended with the background. In this case we now use alpha blending.
Reviewed By: fclem
Differential Revision: https://developer.blender.org/D5340
Add an option to display contour lines tracing through points with the
same interpolated weight value in weight paint mode. This can be useful
for working on gentle gradients over a relatively high resolution mesh,
where the difference in color between adjacent vertices is very small.
The contour grid has 3 levels of detail going down to step 0.001,
which automatically fade in or out based on the weight gradient.
Fade out works by capping both screen space and weight space line
width, and reducing alpha when the screen space width becomes too
small for moire and noise-less rendering.
Reviewers: fclem
Differential Revision: https://developer.blender.org/D3749
Move the weight paint drawing to the fragment shader. The shader
uses a texture that uses the U.coba_weight custom color band, or
an internal color band.
In addition to actual weights, the shader has to display two
alert colors: missing vertex group, and zero weight. The zero
weight alert has to be blended with regular weight colors,
so that a single alert vertex surrounded by weighted ones is
still visible.
Reviewers: campbellbarton, fclem
Differential Revision: https://developer.blender.org/D3675
