Question: Voronoi 3D, continued

This is more or less my first try with grasshopper, and it hasn't been easy. The climb has been steep, but the payoff seems quite worth it.

I have a ton of issues with this design and hence a ton of questions. I’ll start with what I think is the biggest, although I’m guessing the solution won’t be too difficult.

I've gotten this far by studying files posted here. Some of what I have comes from copying chunks from others. Consequently I don’t entirely understand all of my own algorithm.

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Although I’ll attempt to be as clear as possible, looking at this PDF  may be clearer. 

Questions.pdf

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My design uses a Voronoi component. I use a Solid Intersection component to cut it to the shape of the base part.

The base part has lines delineating the different faces. As the algorithm proceeds, there’s no differentiation between the edges of the voronoi cells and the lines of the faces of the base part. So the baked part has stray lines inherited from the base part. How do I get rid of these?

Bracket.3dm

Bracket.gh

Alternately, I've been trying another route using a Split Brep component. I've baked it and manually deleted all of the faces outside of the base part. I have three questions:

How do you separate the faces outside the base part from the faces inside the base part?

How do you turn the inside faces into 3D voronoi geometry

And what the hell is a brep? Is that grasshopper speak for solid body?

One final thing: I’m not married to my approach. If there is a solution that is completely different from what I’m doing and may work better, I’m very interested in hearing it.

Thanks!