Incremental 3d Convex Hull

Thanks to some theory on http://www.cse.unsw.edu.au/~lambert/java/3d/incremental.html

I managed to script an incremental 3d convex hull algorithm.

This is a part of "in-progress" script for k-means rationalization.

It's quite fast (1000 points in cloud = 1.1 sec, amd x6), accepts multiple branches/hulls, most complex math operation is sqrt(2) :) , and its really simple to use (one input, one output) ;)

Replies to This Discussion

Permalink Reply by Michael Pryor on May 4, 2012 at 7:53am

really great work

Permalink Reply by David Stasiuk on May 4, 2012 at 6:05am

Fantastic! Thanks for sharing this...really fast and fun to play with. Also, for Rhino 5 already, and I'm pretty sure for Rhino 4 in the next GH release, IsPointInside has been fixed.

Permalink Reply by Mateusz Zwierzycki on May 6, 2012 at 9:35pm

thanks for comments,

there is so much more to do with meshes in gh: http://en.wikipedia.org/wiki/Conway_polyhedron_notation

I think I will try my best to implement these notations to gh... there is one major problem - no polygonal meshes in rhino...

after finals (only 40 days)...

Permalink Reply by Matt on May 24, 2012 at 4:12am

There may be a very simple answer to this but would be greatful for any help, I'm a complete beginner in grasshopper. I've been playing around a bit with this script and now I'm trying to use it to generate a truss system similar to something like this http://designreform.net/2011/03/rhino-grasshopper-parametric-truss-... that uses the divisions of the hull mesh as the basis for the trusses instead of a shape mapped to a surface (so... not really similar at all). Anyone have any pointers on how I could go about trying to do this? I've tried to decompose the mesh and make polylines with the verticies but then I don't know how to offset them properly. I've tried an offset on srf but I can't use the mesh faces as surfaces. I attached an image showing my scripting attempt A, how I want to offset B and sort of my final goal C. As I'm sure you can tell I'm pretty clueless, any help would be greatly appreciated. (and thank you for the script!)

Attachments:

grasshopper.jpg, 154 KB

Permalink Reply by Mateusz Zwierzycki on May 24, 2012 at 4:31am

use weaverbird :

1. create hull

2. use picture frame component

3. then add thickness component

fin!

Permalink Reply by Matt on May 24, 2012 at 4:55am

Brilliant, exactly what I was looking for! Thanks so much for your help.

Permalink Reply by epee du bois on February 7, 2013 at 11:36am

Hi Mateusz and others,

Thanks for the convex hull definition.

I just wanted to share this use of your script. I used it to perform rotations on a irregularly shaped Brep to approximate the effect of gravity. I needed to find a rotation that would be suitable for further stress tests. The script finds the four polygons with the largest surface area and lets you reorient your brep to accordingly. The should help minimizing loads and would probably be helpful for 3d printing as it allows the user to efficiently find the minimum Z value for an arbitrary form.

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