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| | Constructive Solid Geometry (CSG) (Site not responding. Last check: ) |
 | | CSG is a very powerful concept for object modelling in automation procedures for building extraction and for 3D city models, especially well suited for objects which are relatively simple and show symmetries, because many buildings can be represented by a combination of simple basic building primitives. |
 | | CSG trees are always guaranteed to represent valid objects, they are unambiguous but not unique: each CSG tree models exactly one object, but the CSG tree of a given object is not unique because an object can be built in several ways. |
 | | First, the CSG primitives have to be converted to boundary models, and then these models have to be combined using the Boolean set operations, which, as already stated in section 2.3.1.3, turns out to be very complicated. |
| www.ipf.tuwien.ac.at /fr/buildings/diss/node38.html (529 words) |
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