Collecting outside points

quick question, and hopefully not a stupid one. I have a custom 3d cellular automata script i wrote in rhinoscript and i would like to take each cell and dispatch only the outermost faces to apply a pattern to them. i attached a quick image of the outside faces. thanks everyone.

Attachments:

outside faces.jpg, 600 KB

Replies to This Discussion

Permalink Reply by Mateusz Zwierzycki on May 8, 2012 at 8:09pm

Belive or not, these are only outermost faces :

If you want to delete faces which are top or bottom one, cull them by face normal at (0.5,0.5) parameter (eval surface component) - if normal vector's z value = 0 then true, else false....

EDIT : there are no stupid questions, except that which can be answered by searching forum ;)

Permalink Reply by Aaron Coffman on May 9, 2012 at 8:37am

hey mateusz thanks for the reply. the definition is close but perhaps a larger group of CA cells would help better. here is just another image to show the cellular automata growth at 10 long x 10 wide x 25 high. the highlighted faces are the ones i would like to dispatch and get.

Attachments:

outside faces.jpg, 800 KB

Permalink Reply by Mateusz Zwierzycki on May 9, 2012 at 9:40am

This one should do the job...

Approach in two steps :

cull bottom and top faces first
use convex hull to determine which faces are outermost

You can achieve same effect with top and bottom faces by using 3d convex hull*, which will not require sorting point by z value (there is a little script which puts points in data tree according to their z values).

*To obtain 3d convex hull, complete quest ;) - "search forum for incremental hull" , where you can find my last script for making such geometry

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