# trimmed nurbs srufaces

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Can anyone point me in the direction of some info on trimmed nurbs surfaces? I can't find much info on the subject. I'd like to know the basic math behind them.

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http://www.research.att.com/~krishnas/dissertation.html

The first link is to Shankar Krishnan's dissertation, "Efficient and Accurate Boundary Evaluation Algorithms for Sculptured Solids", and involves trimmed NURBS surfaces.

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Thanks,

You wouldn't happen to know where I could get more info on how curves are projected onto the nurbs surfaces would you?

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Quote:
 Original post by indigox3Thanks,You wouldn't happen to know where I could get more info on how curves are projected onto the nurbs surfaces would you?

A prerequisite problem is to project a point onto a surface. There is no single answer. As a mathematical problem, if the point P is close to the surface, locate the surface point C that is closest to P. This is a difficult algorithm to implement and make robust. If you have a curve of points P(t) for a parameter t, then you get a curve of projections C(t). Now if your surface is the graph of a function, say z = f(x,y), then P = (x,y,z) can be projected to (x,y,f(x,y)).

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