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indigox3

dumb question about nurbs

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I'm not too familiar with NURBS and b-splines, and I'm confused about what the difference is between a bezier patch and a NURBS surface? I understand that a bezier patch is like a grid of bezier curves, and evaluating a point on the surface boils down to evaluating the curves in the U direction, then in the V direction. How does this differ from a NURBS surface? Just in the type of curves that define the surface?

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I'm looking at this kind of stuff at the moment for terrain. Apparently the difference between a bezier patch and a nurbs surface is that a nurbs surface uses "knots". It's in all the tutorials on nurbs I've come across.

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Knots are properties of nurbs curves and not Bezier curves correct? So then the difference between bezier patches and nurbs surfaces really is just that the curves are of different types?

(and do the terms "patches" and "surfaces" mean the same thing?)

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from what I can recall points for a bezier curve plot a convex outer hull tapping in a simple(ish) equation yeilds a curve.

I think points for a NURBS surface have associated weight, the curve only touches the first and last points and is distored by the weight of each nurb point (like gravity)

I used bezier splines for animation paths, but I needed to re-integegrate for time in order to get consistent speed of the animated objects. I dont know whether NURBS require this and I don't know how to calculate the curve once it has been distored.

If someone in the know could continue this thread it would make an interesting read [smile]

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