How can I project lines perp to surface or to nearest surface?

Is there a way of selecting curves and circles and projecting them perpendicular to the surface nearest them.

I need to explain this a bit more !

In simple terms if I have a football, lets say the type with hexagons all over it, and I use photogrammetry to capture those hexagons in 3D and then import to Rhino, I then draw a sphere within that shape and the lines are varying from 1 to 3mm beyond the sphere, some even wander just inside it, due to the vagiaries of photogrammetry !!!,  projecting the lines in ortho view will see those at the top on the sphere go beyond where they should go. Projecting to nearest surface or perp to surface will fit them back on correctly.

The actual project:-
I have panel lines and rivet circles created using photogrammetry of an aircraft, so we have a pretty fair shape but its not as perfect as drawn with curve tools in rhino. I then create the surfaces using this data as a guide. I then need to project the photogrammetry curves etc onto this better surface. As it relates to this surface in a way that is perp to the surface, it needs projecting onto that surface in that same way.

If the tailwheel bay edge is a curving line 2mm out from the surface and I project it in ortho port side view, it will make a line on the surface well away from where it should be, but if I project it in a way perp to surface, I will get the correct shape back on the surface.


That’s the Pull command you’re describing.

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Just what the doctor ordered :slight_smile:


Many Thanks indeed :slight_smile:


Hi John,

Is there a way to do this in Grasshopper?

I am trying to solve a similar problem but came at it from a slightly different starting point.
Project Multiple Surfaces to Faces (Windows to Walls) - Grasshopper - McNeel Forum


No idea. I don’t Grasshopper.

I’d suggest posting a question about “Pull” in the Grasshopper category instead of effectively hiding it here.

Yes, Grasshopper has a Pull command that will pull a curve onto a surface.

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Great! Thank you!