Diff Comparison of Eye Diagrams

[mpangch]

Given multiple eye diagrams, create a nice way to overlay them graphically so as to offer an easy to understand visual comparison.

[azonenberg]

This is probably best implemented as a filter block (under scopehal) that turns two eye patterns into an eye-like density map but using a different shader for rendering. Leaving the ticket here for now as rendering work is going to be needed too, we may eventually file a second ticket on the scopehal side.

The output would be a 2D grayscale signed fp32 texture, storing differences between normalized eye intensity at each pixel. This could then get tone mapped to a diverging color scale (for example, black = no difference, brighter shades of red = eye A is stronger, brighter shades of blue = eye B is stronger).