Shrink trimmed Surface in Grasshopper

I’m looking for a solution to shrink a surface to the trimmed boundaries. I know there’s a way to do it in Rhino, but I’ll prefer to keep it in Grasshopper to stick to the parametric idea.

This is the Surface / GH untrimmed:

and now trimmed:

As you can see I’ve tried to use cull pattern to just have the trimmed surface / or use the polyline to cut the surface, but it didn’t work.

When I bake the surface and activate points in Rhino it show’s the full untrimmed surface, which I need to shrink to the bounding polyline


There’s no Shrink component in the native toolset, but you can do it in C# (10.1 KB)


Thank you,
but it’s not working for me or I’m doing sth wrong.

Here’s the simplified GH file with the shrink already embedded
Shrink (16.8 KB)

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I don’t have LunchBox installed, but your surface appears to already be untrimmed. It cannot be shrunk further.

I guess that is my problem. It’s trimmed in Grasshopper but Rhino doesn’t accept that by looking at the points forming a rectangle.

I’m not sure what that would be.

Any NURBS surface will ALWAYS form a rectangle. By shrinking it, the points will get as close to the trim curve as possible, but unless the trim curve is exactly along the points grid, there will always be points sticking out of the trimmed edges.

This is an old discussion, but maybe, I encountered a way to do what do you want.



Hi Natalia,

Interesting solution have been trying to resolve the nurbs-isotrim issue - what component was used? If you can share the definition here please - would be appreciated :slight_smile: