Huh sorry I meant like this...

I should have said convex and non-convex to be precise - but I did say closed, didn't I? ;)

Rough definition of convex : if you have a region (2d or 3d), take two arbitrary points within it and draw a line. If the "shape" is convex the the line will never cross the region boundary.

so a sphere or a cone are convex, a torus isn't.

Thanks for your input Dany, always first on deck to help people in trouble. But I'm not a beginner really! I'm thinking actually I might move this post to the vb forum. It must have been implemented in some open library. I hope...

There's nothing ready made for this. One interesting approach could involve Convex hull. If a curve is purely convex, it will be similar to the convex hull of all the points that make up the curve. Also if a curve is convex it means its control-point-polygon will also be convex. Comparing the control-point-polygon to its own convex hull may give you the answer.

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David Rutten

david@mcneel.com

Poprad, Slovakia

Hi,

Once I had a quite similar question,

how one could "read out" the results of the crvgraph into a list.

angelos