Problem with surface in ghPython

Hi everyone,

I am confused with the way ghPython processes a surface.

Please see the attached chart. All I did was to set the surface as a return value (s). But the actual result becomes a surface in rectangular. I thought it should be the original surface.

Due to this problem, I cannot use ghpythonlib.components.SurfaceSplit method in python. The shape that would be splitted is the rectangular. But the grasshopper component "Surface Split" in intersect tab works well.

Thank you.

-------- My rhino env is as below. --------

Rhino: 5 SR7

Grasshopper: 0.9.0066

ghPython: 0.6.0.3

Replies to This Discussion

Permalink Reply by djordje on January 16, 2014 at 12:17am

Hi Tabaoman,

You may need to Shrink the surfaces.
Could you attach your .3dm and .gh files please.

Permalink Reply by tabaoman on January 16, 2014 at 12:22am

You mean my surface is so big that it need to be shrinked? Sorry, I don't get the point.

Please find the files.

Thank you.

Attachments:

exercise.3dm, 22 KB
exercise.gh, 5 KB

Permalink Reply by djordje on January 16, 2014 at 12:44am

No, not that. Trimmed surfaces control points usually remain outside its boundaries. That's why you need shrink them. Use the ShrinkFaces() method:

if S.Faces.ShrinkFaces():
s = S

Attachments:

exercise2.gh, 4 KB

Permalink Reply by tabaoman on January 16, 2014 at 12:52am

Hi Djordje,

Thanks for your valuable replies.

For the shape I gave, ShrinkFaces always returns false. That means I cannot get the extact shape (circle-like) in python code. Am I right?

Permalink Reply by djordje on January 16, 2014 at 12:58am

Did you download the "exercise2.gh" file? You need to change the "S" type from "Surface" to "Brep". "Surface" type does not have the ShrinkFaces() method.

Permalink Reply by tabaoman on January 16, 2014 at 1:03am

Sure. I see.

I considered SURFACE too much.

Djordje, thank you very very much. :)

Permalink Reply by Giulio Piacentino on January 16, 2014 at 2:35am

Yes, Djordje is exactly right.

Surface's (or NurbsSurface's) defined 2-dimensional objects. Nurbs are inherently rectangular. Brep's (Boundary REPresentations) on the other hand can cat out parts from these, and give you other shapes.

I hope this helps

Giulio
--
Giulio Piacentino
for Robert McNeel & Associates
giulio@mcneel.com

Permalink Reply by tabaoman on January 16, 2014 at 5:49pm

Clear. I know those basic concepts better.

Thank you, Giulio.

BTW, Rhino for Mac is on-going. Do you know how to join the development?

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