Offset Curves from Deconstructed Brep

This is so basic, but I'm not sure what I'm doing wrong.

I want to deconstruct a brep with planar surfaces, then offset the borders of those surfaces inward. Some curves offset correctly, while others reverse direction. I'm guessing this is an issue with the plane direction?

On the right is the resulting geometry I want, hand-constructed in Rhino.

Attachments:

offset.3dm, 48 KB
offset.gh, 10 KB

Replies to This Discussion

Permalink Reply by Joseph Oster on June 9, 2015 at 2:56pm

You are offsetting the faces instead of the edges.

And your offset plane is 'World XY' so the vertical corners aren't affected.

I think you'll need a different solution.

Permalink Reply by Matt Heinzler on June 9, 2015 at 3:09pm

Thanks for your reply. Using the faces seems to extract the closed polylines automatically. When I use edges, there aren't enough curves to offset. Would you mind showing a solution?

Permalink Reply by Pieter Segeren on June 9, 2015 at 3:11pm

Hi Matt, your initial definition is fine (indeed automatic conversion), just put the faces in the Offset P (Plane) input too:

Permalink Reply by Joseph Oster on June 9, 2015 at 3:25pm

Wow! That's clever - though, fairly non-intuitive.

I tried a couple different alternatives including scaling the brep using its 'Bounding Box' center, but that wasn't right either. This is cool - good to know.

Permalink Reply by Joseph Oster on June 9, 2015 at 4:04pm

Ouch!

Permalink Reply by Joseph Oster on June 9, 2015 at 5:01pm

Hey Pieter, it was discouraging and, I think, unnecessary. I appreciate what you know, thanks. Many of the clever features of GH are certainly NOT intuitive to people learning it - and there is a _LOT_ to learn.

Permalink Reply by Joseph Oster on June 9, 2015 at 4:58pm

P.S. Just to complete the picture:

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