it routinely checks for regressions by rendering maps before and after a change and looking for pixel-level differences

I don't know about 3D, but I have been extensively using Fable (with Opus as sub-agents) for https://trailmaps.app [1] and it routinely checks for regressions by rendering maps before and after a change and looking for pixel-level differences. That, and as I used it to work on the transit-style line drawing plugin [2] it would use the same technique both to test against regressions and look for improvements in the algorithm. …