Beginner question - how to extrude a surface without creating internal faces?

Hello,

I'm just getting familiar with Grasshopper, and having a great time. I have run into one roadblock around extruding flat surfaces that I hope someone can help me with.

I've created a pretty basic surface (please see the first attached image)

So far, so good.

However, when I extrude that flat surface, I end up with a bunch of internal faces (please see the second attached image)

How can I set up an extrude that works correctly - that does not create internal faces?

Thank you in advance for your help!

Replies to This Discussion

Permalink Reply by Brent Watanabe on September 29, 2012 at 11:04pm

When you make your surface, don't include the interior curves. Cull those out.

Permalink Reply by Michael Pryor on September 30, 2012 at 12:25am

Join the surfaces first. Or join / union the breps after

Permalink Reply by Al Krever on September 30, 2012 at 10:57am

If this was your end point, then you could bake the object. Once baked use the extract surface command in rhino to extract the interior surfaces and then delete them.

If this is an interim step this would not be the way to go.

Permalink Reply by Elliot Blanchard on September 30, 2012 at 9:26pm

Hello Al,

Great to hear from you - and thank you for your help. When you mention extracting the interior surfaces using the extract surface command - is that something that would be done by manually selecting each interior surface - or is there an automated way to do that?

Thanks again,

Elliot

Permalink Reply by Al Krever on October 1, 2012 at 12:23am

Hi Elliot:

I typically select them during the extract surface command and then delete them. I'm not sure that one could automate that. I don't know how I would differentiate between the internal surface and all the other surfaces.

all the best

Permalink Reply by Michael Pryor on October 1, 2012 at 1:33am

because typically an internal surface in this case is a duplicate. See below. also the more computationally heavy way of unioning will remove interior surfaces in grasshopper and rhino as well.

Permalink Reply by Michael Pryor on September 30, 2012 at 1:23pm

This way is faster than any booleaning + is relatively simple.

Permalink Reply by Elliot Blanchard on September 30, 2012 at 9:24pm

Hello Michael,

Thank you so much for your reply. Could you perhaps share that example file that the screenshot is from? I've tried to recreate it, but I must be making a mistake at some point - the interior faces are still there at the end of the process.

Thanks again,

Elliot

Permalink Reply by Michael Pryor on September 30, 2012 at 10:06pm

set dup points to cull all. If not you upload your specific rhino file and definition.

Permalink Reply by Elliot Blanchard on October 1, 2012 at 12:16pm

Hello all,

Here's my rhino file and definition - again, much appreciate any and all help and suggestions.

Thanks again,

Elliot

Attachments:

Extrude_23_simple.gh, 22 KB
Extrude_base_22_simple.3dm, 1.2 MB

Permalink Reply by Elliot Blanchard on October 2, 2012 at 10:15am

I think I may have made some progress using a slightly different approach. I exploded the brep resulting from the extrude - the shape with the multiple faces - then used a dispatch with multiple booleans to eliminate the unwanted interior faces, as they seem to follow a repeating pattern. Does that sound valid?

Thanks again.

Permalink Reply by Michael Pryor on October 2, 2012 at 10:29am

my method works just fine on your example.