| __Combinatorial Solid Geometry, Boundary Representations, and Non-Manifold Geometry__ *(Site not responding. Last check: 2007-11-07)* |

| | **Solid** models differ from drafting-type systems in several important ways: objects are composed of combinations of primitive objects (some quite complex), each of which is complete, unambiguous, physically realizable, and modifiable. |

| | For example, the **geometry** information associated with a planar face is the plane equation which includes the outward-pointing surface normal; the plane equation does not have to be re-derived from the vertices. |

| | Therefore, the conclusion was that the existing combinatorial **solid** **geometry** database would remain unchanged, and that any application that required an explicit representation of the modeled shapes would obtain that explicit representation through some form of conversion of the underlying CSG database. |

| ftp.arl.mil /~mike/papers/90nmg/joined.html (20066 words) |