Trim 2 Breps

Hi,

I looking for a simple function to trim 2 breps against each other.

Basically, I want to split the green cylinder(smaller) with the surface of the blue (larger) cylinder and keep the larger part of the green.

I know there are Brep/Brep intersections to get the intersecting curve. Does anyone know how this intersection curve can be eventually used to split the Brep?

The Rhino command "trim" seems to take care of this problem. What does this "trim" command do and can we replicate this with code in GH or existing components?

Thanks.

Kermin

BrepTrimQuestionjpg.jpg

Attachments:

BrepTrimQuestionjpg.jpg, 150 KB

Replies to This Discussion

Permalink Reply by taz on August 3, 2011 at 5:48pm

Split can be fickle...

You could extend your intersection curve and then project it back to the surface you want to split. That should work.

Permalink Reply by kermin chok on August 3, 2011 at 9:10pm

Sounds like an approach. I'll try it out.

Does anyone know if the native "Trim" command in rhino performs this sequence of operations in the background so the command works?

If we can simply replicate the operations that the Rhino-Trim command does, it should be easier in the future.

Permalink Reply by Moonbeast on August 3, 2011 at 10:44pm

From your image it looks like you have to cylindrical surfaces, which is good. You can use brep/brep intersect to get the curve and then split the green surface with the curve generated by the intersect, lastly cull out the surface that you want to keep.

This Definition should work for you, keep in mind the split will only work for a surface not a polysurface/brep

Attachments:

Trim Surface.ghx, 81 KB
Trim Surface.jpg, 412 KB

Permalink Reply by kermin chok on August 5, 2011 at 12:43am

Hi,

Thanks for the input.

In the end, I used the Rhinocommon function Brep.split. Most of the time it worked except for figuring out which end of the trim or split to keep.

Also tricky was the fact that if this function fails, it returns "nothing" instead of a zero length array which wasn't clear to me at the beginning. This was causing some major fails.

Permalink Reply by amir on November 10, 2011 at 6:46am