# Getting intersection of tangent surfaces

Rhino seems to have a real struggle to find intersections of tangent surfaces. Are there any tricks to getting the intersection commands to work in Python more reliably? I’ve tried playing with tolerances but some surfaces will find intersections with a higher tolerance while others work with low tolerances.

Currently I’m struggling to find the intersection between these two surfaces. The big surface is a flat plane. the smaller one a swept arc. As far as I can tell the edge of the swept arc is planar and aligned with the flat plane.

Any help with this would be greatly appreciated.
Thanks
Ian

This might be a tolerance issue.
It’s impossible to know for sure without a 3dm file.

Hi Ian - I think this will be hard - as JB points out, it is subject to tolerance and the edge is just, barely, in theory, coincident with the surface. In regular old Rhino, trimming in this situation is generally much more reliable just using the edge curves directly (DupEdge or sub-object select or filter with the CRV selection filter) .
What are you trying to do in Python? Can you use the edge curve?

-Pascal

Pascal,

I am trying to make a parametric model from multiple surfaces. Becuase the geometry has so many variations its hard to define the cutting edges so I figured using intersect between adjacent surfaces would work. I could then use the intersection curves to trim off the excess.

Using Python is there an easy way to select specific edges of a surface? I would have to rewrite my routine but if there is a logical way to select edges I might be able to go that route instead of using intersect.

Thanks

Well… logical might depend …things, but you can get the surface as a brep.Faces[0].Edges - these each have an index, and a curve and so on … PM me if you like with a bit more about what you are up to and I’ll help if I can.

-Pascal