Nested 3D Voronoi aka Convert Mesh to Brep?

Hi,

I try to create a nested 3d voronoi. In more detail, from a standard (rather coarse) 3D voronoi, I want to use the edges of the cells (a bit thickened and smoothed so they look good) as the diagram boundary for a much more fine-grained voronoi. So it may be similar to the 2D voronoi groups, but not really.

I managed to create the points within the geometry, and build a fine-grained voronoi diagram, but could not cut it down using SDiff.

Now I have a few questions:

1. Is there a better method to create the points? Because first generating thousands points in a bounding box and then throwing away 90% of them is quite time consuming and doesn't seem to be an elegant way.

2. Is there a good method to convert a mesh into a brep? Then I could use SDiff to get me a result (but I'm still not sure if that is exactly what I want)

3. Is there overall a better/smarter approach to the problem?

Thank you very much for your help :)