I kept running into the same problem: image-to-3D tools produce relief
panels with unusable topology. Uneven triangle density, stretched faces,
half the geometry wasted on a back plate. Retopology tools smooth them out
and lose the detail you were trying to keep.
Relief Rebake takes a different route. It samples the object from above
onto a regular grid, cleans up the height map, and rebuilds a fresh
watertight mesh with even quads, straight side walls and a flat base.
Every height value is kept; only the grid underneath is replaced.
The output is a plain quad grid, so it displaces, subdivides, sculpts and
exports to CAM cleanly.
Version 1.2 replaced the per-pixel ray caster with a vectorised sampler.
On a 694k-vertex relief the old path took about 65 minutes at resolution
4725; the new one takes under a second. Ray Cast is still there as an
option for meshes with real overhangs.
It also reports the source mesh resolution and warns when the requested
resolution is far above it, since anything past that only interpolates.
Requires only numpy, which ships with Blender. Tested on 4.2 through 5.1.
Free under GPL v3.
Extension page: https://extensions.blender.org/add-ons/relief-rebake/
Source: https://github.com/agregarts/relief-rebake
Feedback and bug reports welcome.