[Feature Request] Support Multiple Region Brushes

[4LT]

I was playing around with region brushes, discovered that it only supports cases of single region brushes:

---- LoadMapFile ----
�[38;2;255;000;000m************ ERROR ************
ParseBrush: Multiple region brushes detected; newest at }
�[0m#### Finished with exit status 1

I understand this is beyond the scope of the original intent of this tool, but I was hoping that I could include that I could include an L-shaped region of my map by using two intersecting region blocks (i.e. the CSG union of the two brushes).

I get that I could accomplish the same thing with a region and an antiregion brush, I just think it would be intuitive if it worked this way.

[Paril]

The reason for this is that generating a region brush is a bit more complex (since the region brush is expanded into 6 brushes - a hollow box) and I'm not sure offhand how I would handle the case of generating more than one of them together.. probably some kind of CSG, I dunno.

Anti-regions are inherently more powerful because it doesn't have that limitation as the brush itself just goes from A to B without any additional processing.

[ericwa]

I forget if we have a “csg_subtract(brush list, brush list) -> brush list” in the codebase but I think we could just subtract all the region brushes from a solid box the size of the map?