On Wed, Jul 17, 2013 at 12:04 AM, phoenix <[email protected]> wrote:
> > If I'm interpreting the bottom part of p.624 and the top of p.625 in
> that paper correctly, we cannot assume this property holds for general
> NURBS or B-Spline surfaces (intuitively I wouldn't expect it to) but if the
> paper is correct we *can* assume this is true for Bezier patches.
> Therefore, if the NURBS surface in question is converted to a set of Bezier
> patches via knot insertion or knot refinement the test may be possible for
> the resulting Bezier patches. Of course, the challenge is then to take that
> information and relate it back to the NURBS surfaces, since multiple
> patches will potentially need to be "stitched" into the final NURBS overlap
> boundary curve.
>
> Yes, you are right. The current idea is to get the boundaries of the
> continuous patches (e.g. Bezier patches), use curve-surface intersections
> to find the overlap curve, and finally stitch them together. (Maybe
> ON_NurbsCurve::Append() can stitch two NURBS curves together if they share
> an end point?)
>
I'm not sure how Append works for curves - probably worth testing. But
remember you have another challenge for something like that - recognizing
when a curve-surface intersection is not actually part of the outer loop
but is instead an "inner" curve segment. One approach might be to maintain
a 2D "grid" of unit squares that maps to the Bezier patches and corresponds
to their "flattened" topology - using that to track the edge status
(intersecting/not-intersecting/partial) should make it much easier to
determine when a particular edge is part of the final "outer" loop.
CY
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