BRL-CAD is a CSG (constructive solid geometry) package, as they really wanted to work with solids: so that they could model penetration of ballistic objects into tanks and so...
What I'm totally not in a position to judge: could this be used for IFC ("information for construction", an building/construction/architecture building model standard with a big CAD background)?
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My name is Reinout van Rees and I work a lot with Python (programming language) and Django (website framework). I live in The Netherlands and I'm happily married to Annie van Rees-Kooiman.
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