3D Convex Hull as Brep

Hi,

I am looking for a way to create a convex hull in 3D from a set of points as a brep. I searched the forum, but I had the feeling that most posts are quite a few years old, and maybe things changed by then. The most promissing I found was this nice thread:

http://www.grasshopper3d.com/forum/topics/incremental-3d-convex-hul...

But here only a mesh is generated, but since I want to continue working with the hull as brep, I thought there might be an easier way to do that.

Any suggestions?

Thanks very much!

Replies to This Discussion

Permalink Reply by Mohamed Naeim on August 11, 2016 at 6:49pm

http://www.grasshopper3d.com/group/starling

Permalink Reply by peter fotiadis on August 12, 2016 at 12:09am

Well...

1. After creating random (or with some other logic) points on a brep you'll need some ball pivot (BPA) method (not Delauney at least with regard "solid" results) to triangulate them, say like this:

BPA was invented in IBM Labs long time ago for addressing reverse engineering problems (scans and the likes). If I remember correctly some good Samaritan provided a BPA of some sort some time ago (but this occasionally hangs GH for some reason). In some countries BPA is patented.

2. BPA yields a mesh (open or closed) or more (open) depending on the topology and the search radius.

3. If a brep is the target you can get the mesh faces and define BrepFaces out of them.Then "stitch" (join) them getting an open or closed brep respectively.

4. Or you can use in some script the Brep.CreateFromMesh(mesh, trimmedTriangles) Method.

Permalink Reply by peter fotiadis on August 12, 2016 at 2:15am

And regardless BPA matters and if you have a mesh on hand ... this attached does the Mesh > Brep job (read the WARNING).

Depending on the splitDisjoined bool value you get one or many breps in a Tree. The "small" C# removes randomly mesh faces (for fun) if the percentage is < 100.

Load rhino file first for the demo cases

Attachments: