# Find the U or V direction at given points on a surface

Hi there.

As you can see in the picture I have been trying to find the U an V vectors at certain points on a surface. I gathered that in many cases it is enough to use the “dePlane” component after an “Evaluate Surface”. X and Y would be representing somewhat the U and V direction of the surface at that point. But I have come across a few cases (like this one) that isn’t enough. In Reality the U and V directions of a surface are not necessarily perpendicular to each other, whereas the axes of a plane always are.
(David has already pointed that out some time ago, http://www.grasshopper3d.com/xn/detail/2985220:Comment:24774)

So…How can I find the real U or V direction at a point on a surfaces?

Any thoughts?

finding_UVdirection.gh (11.7 KB)

Hi,
You may use the IsoCurve Component to extract curves in U and V directions.
Then Evaluate these curves to find their tangent vector at each position you need.

1 Like

Great wisdom!

Thanks a lot!