Selecting only the top surface from a list of breps

Replies to This Discussion

Permalink Reply by Andrew Heumann on July 9, 2011 at 5:43pm

I usually do this by taking the normal of each face and then the dot product of the normal and the z axis. 

 

 

Permalink Reply by Aaron on July 9, 2011 at 6:49pm

Thanks Andrew. I tried it that exact definition with the attached file, but didn't get the expected result. Does it work for you?

Attachments:

• top surface test.3dm, 138 KB

Permalink Reply by Andrew Heumann on July 9, 2011 at 8:12pm

Oh sorry I had assumed all of the volumes were closed, which guarantees that the normal vectors face out - to get all surfaces that are roughly parallel with the XY plane, feed the absolute value of the dot product into "A" in the Larger component. 

If your volumes are closed this will also give you the bottom, but in your case I think it's what you want. 

Permalink Reply by Aaron on July 9, 2011 at 8:18pm

That's it! Thanks Andrew!

Permalink Reply by Andrew Heumann on July 9, 2011 at 8:15pm

And here's another approach that might be simpler. 

 

Permalink Reply by Aaron on July 9, 2011 at 8:43pm

Cool, both work great! I must admit, I understand the second one more easily.

Permalink Reply by ndy_123 on March 6, 2016 at 5:17pm

Hi, I had the same problem but cannot find one icon...whats pComp in long term? Thank you.

Permalink Reply by Ahmet Can Karakadılar on December 22, 2017 at 1:35am

It's deconstruct, pDecon.

Permalink Reply by Ben Pearce on September 15, 2014 at 9:23pm

That's awesome! Thanks a bunch.  I knew dot products were good for something.

Permalink Reply by amir on March 8, 2012 at 8:46am

simple , love it, thanks aaron !