Extend a trimmed surface

Grasshopper
1

hi there,

I try to extend a trimmed surface but I’m experiencing some issues. The trimmed surface become untrimmed..

ExtendSrf_cc_1.gh (104.0 KB)

. How to overcome this?

image
image1764×1760 309 KB

To my knowledge the only component I saw for this purpose is the one written by david rutten 10 years ago. Extend surface?!?! - #12 by Mahdiyar . Is it correct? Any plugin might help ?

thanks!

CC

2

This is mainly to answer the question rather than provide a ‘solution’:
On numerous situations the cheat is to re-create the surface as untrimmed via edge curves. This can work when you have no more than 4 curves.

For this object, I just used brep edges. However, sometimes to break the border into the four edges, the discontinuity + shatter combo is the way to go, then edge surface followed by a surface from points if you must pull the surface points back to the original shape.
ExtendSrf_cc_1.gh (102.3 KB)

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image1713×265 62.4 KB

Regardless of the method, the shape is just as crucial, if not more, as you sure know - any value beyond a subtle extension will mess up this surface inevitably. Another similarly limited workaround is to choose to extend the edges via something like Extend Crv, prior to forming the new untrimmed surface. This might help skip the surface extension while quality is still contingent on overall shape.

Lastly, regarding plugins to extend surfaces, I think…sasquatch has a component? Pufferfish? Same difference.

Cheers!

3

*Forgot to mention ruled surface and/or contouring the original brep then lofting the lines, to regenerate your trimmed surface as untrimmed. I tried those but they were less consistent. Edge surface + surface from points had more fidelity.

4

Thanks for the great explanation @René_Corella. I think inevitably we have to reconstruct the surface.

Stil i’ll have to make sure that it is perfectly inline with the original shape because in my defnition I have to merge couple of these shapes and they need to perfectly share same edge. I was facing other issues here Merge surfaces (trim and untrim) sharing same edge

Ill go on with this. appreciated.

CC