Closed Brep from list of points

Starting with two non-coplanar polylines, I am trying to get the smallest closed brep volume that fits around the vertices such that no line between any two vertices falls outside the volume. I have been trying variations of triangulation to produce the surfaces, but selecting only the outside surfaces from all the permutations and joining them has been a problem. I also tried extruding triangular surfaces from one polyline to every point on the other polyline, then boolean unioning the result, but the union often fails. It seems that their might be an easier way out there. Any thoughts?

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CLOSED BREP.png, 36 KB

Replies to This Discussion

Permalink Reply by Andrew Heumann on June 20, 2010 at 11:48pm

I believe what you are talking about is a 3-dimensional convex hull, which is a well-established problem in computer graphics. qhull (http://www.qhull.org/) is capable of this calculation given a set of vertices, and I know dimitrie stefanescu has successfully linked grasshopper with qhull (see here: http://dimitrie.wordpress.com/2009/05/01/3d-voronoi-in-grasshopper/) for the purposes of calculating 3d voronoi. To my knowledge, however, no one has as of yet put together a definition or a link with qhull for computing the 3d convex hull in grasshopper, although my instinct is that it would be fairly easy for someone with coding experience to modify dimitrie's work to achieve that goal. That said, I gave it a quick stab myself at one point and gave up before I got any useful results.

Sorry I don't have an easy solution to your problem, but I hope this gives you some hints as to where to start looking!

Andrew

Permalink Reply by Jeff Niemasz on June 22, 2010 at 11:06am

Thanks Andrew. I think you are right that the 3d convex hull is the volume that I am looking for. Dimitrie's 3d voronoi component works well, I am going to mess around with it to see if I can get the convex hull.

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