For mesh simplification, what about https://github.com/wjakob/instant-meshes https://github.com/wjakob/instant-meshes ? I know it does the thing you required, b

For mesh simplification, what about https://github.com/wjakob/instant-meshes https://github.com/wjakob/instant-meshes ? I know it does the thing you required, but it doesn't really do variable density (you could tell it what areas need what density and it would do that; the paper has a demonstration of this).