Fixed it.  I think.  Half fixed it?

It rendered.  Several times.  Buttons do what they’re supposed to.

It still crashes; seemingly always when using a dummy Rift, sometimes when using a real one.  Seems random.  Goes in streaks.  Will look into disabling timewarp — that seems to be what it’s doing when it breaks.

Motion looks strange; I don’t think the distortion-correction shaders are working correctly, chromatic and spherical distortions are very much present.

Otherwise needs some polish.  For instance, after seeing the throwing target in the Rift, I realize I’ll need to work in world instead of view coords.  This means passing in a few more uniforms, or adjusting the origin of the pointcloud scene.

I should probably look into modifying pointcloud scenes, anyway.