Grasshopper is not referencing polysurface or brep


(Fraser Carroll) #1

Hi, I’m trying to use a script that reads a surface and projects a triangular grid onto it, however the surface that Im using wont be read by grasshopper, I’ve booleaned them together and joined them and rhino reads it as a singular surface but grasshopper simply doesn’t? and refuses to allow me to put it in the script.
I’ve tried referencing it as a brep but the script components don’t like that either, anyone got any answers on this?
attached is the file with the surface and the script
surface.3dm (802.4 KB) (3.2 KB)

(David Rutten) #2

Well it’s a polysurface in your 3dm file, which is why you cannot reference it using a Surface parameter. However it looks like it could be simplified into a single surface, and a somewhat cleaner one at that.

If you _Explode your polysurface and use the _What command on the resulting four surfaces, you can see that they are all trimmed. This complicates merging them into a single surface. How did you make them?

(Fraser Carroll) #3

yes I’ve been struggling to work out how to permanently delete the trimmed data and I cant find any solutions so maybe if you have any advice on that I could kill two birds with one stone, the surfaces are a cliff edges that i scale1D vertically, and I’m attempting translate them into an equilateral triangle grid

(David Rutten) #4

Provided the trims are exactly along the iso-curve directions, they can be cut off permanently. You can use the _Split command with the option Shrink=Yes and Isocurve to really cut off part of a surface. But you’ll see that your current trims are not parallel to the underlying uv space.

I’ve ran _Explode, _Untrim, _MergeSrf, _Rebuild on your surface and it gives me the following result: surface_untrimmed_merged.3dm (497.2 KB)

You’ve lost your trimming edges now, but maybe your GH script can handle single surfaces with trims.

(Fraser Carroll) #5

thanks for your help, I really need the original surface shapes though, is there no way to retain those forms and still input them into grasshopper?

(David Rutten) #6

I doubt it, not without a massive redesign of the algorithm in that file. A surface has a single uv domain that is contiguous and smooth. A polysurface is made up of separate patches. They’re mathematically completely different types of geometry. However if you skip the _Rebuild step, then the merged surface should have a similar shape to your original polysurface. You just have to retrim the edges.