U or V isoCurve on Surface?

I just wondering how does the Surface determined which is U and which is V?

Sometimes it is a little bit annoying when I try to find curves on surface...... anyone got explanation or know how to solve this?

Or is it because EdgeSurface component cause the problem?

Attachments:

isoProblemUV.3dm, 93 KB
isoProblemUV.gh, 7 KB

Replies to This Discussion

Permalink Reply by David Rutten on February 4, 2014 at 3:10am

It depends on the type of surface. PlaneSurface uses the axis directions of the underlying plane (x=u, y=v). RevSurface always has u going around and v going up, i.e. the revolution profile is the direction of v. For nurbs surfaces it just depends on how the control-points are oriented.

However surface U V directions can be flipped and transposed, so it's difficult to predict ahead of time which will be which.

David Rutten

david@mcneel.com

Permalink Reply by Gene Kao on February 4, 2014 at 4:03am

:) Thanks David. So in this case it is almost impossible to flip or transpose them into the same direction right? Because too difficult to predict them. For example, v are all parallel with x.

By the way, I didn't really get one of your ideas David... what you said "For nurbs surfaces it just depends on how the control-points are oriented," However, taking a look at the nurbs surface I posted above. Shouldn't curve on surface 1 = curve on surface 2?