Subtraction: Perforating a Surface?

I'm pretty new to Grasshopper and here something basic is escaping me.

I have a surface (extruded to a thickness) and a series of ellipses that are easily projected/traced/extruded through the first surface. I'd like to -subtract- these ellipses from the surface, but it doesn't seem to work. In other programs I'd resolve this by Boolean Subtraction...

But it's not working. Any thoughts? The goal is to create perforations in the surface using the ellipses as a guide... Thx!

Attachments:

090530_Learning_Texture.ghx, 231 KB

Replies to This Discussion

Permalink Reply by J.Filigran on May 31, 2009 at 2:26am

Hello!

I think the Rhino doesn´t like the fact that the center of your extruded ellipses is exactly on the edge of the Brep you want to subtract from. Also the "Surface From Points" you created results in 2 congruent surfaces. Another problem is that you have 1 Brep you want to subtract 49 surfaces from. The result is 49 different Breps with 1 hole respectively.
I tried something - but it requires a lot of computation time. Hence I recommend adjusting the main surface to your liking and then switch "Compute" to true.
I hope this helps you in some way.

Attachments:

090530_Learning_Texture edited.ghx, 2 MB

Permalink Reply by Jonathon Broughton on June 3, 2009 at 5:14am

to avoid the 49 separate split breps issue, we have first made a boolean union including all the subtracting elements by joing with some arbitrary non-intersecting form

then you have one to one relationships between subtracting and subtracted breps

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