Extract non-transparent surfaces after "Color mask"


we need to extract individual surfaces (or meshes) from Color masked render surface. Is in Rhino function for this available? Is an option to do that with Grasshopper?

The link with picture.

Or other possibilities to do that…

Thanks for answers

Check out this thread: How to trace a line drawing image to be a “”real line“ vector drawing instead of a outline image?

  1. Have you tried Illustrator’s Image Trace feature? You can import lines from AI to Rhino in DWG or IGES format. If the lines are too complex when you bring them into Rhino, try running the _Rebuild command on them.

  2. You might be able to get a result by generating a _Heightfield and then cutting a _Section to get 2D lines. Not sure how usable it would be for your needs.

  3. You will have the most control over the quality of the lines if you trace it by hand. I usually lock the image after bringing it in with the _Picture command and bump the opacity down to 50%. I like to trace with the _InterpCrv command. Others like _Sketch and regular ol’ _Curve. This option sounds laborious, but in my experience, it will yield the best result.

No matter which method you use to generate the outlines, you’ll need to have closed curve and polycurve regions to generate surfaces. Use the _PlanarSrf command. If for some reason your curves are not planar after drawing them you can use the _SetPt command to “pancake” them in the Z direction. Another helpful command to be aware of for this task is _CurveBoolean.


thaks for fast feedback. Options 1 and 2 are possible on flat surfaces. On 3D is much more complicated and we need to extract surfaces on 3D base surface. Picture enclosed.

Any suggestion?

BR Lastec

Could you use _Project to get the pattern on the curves surfaces or is there too much distortion?

You could try _InterpCrvOnSrf and manually draw on the curved surface. This still gives you most control.


_Unroll your surfaces, draw the pattern flat and use _FlowAlongSrf to match the curved surface. Keep in mind that this command usually ignores trimmed boundaries. Additionally, you might have trouble lining up the pattern between surfaces.