A question a bout UV surfaces

Hi dears :smile:
How can i specify UV of my surface ,for example i create a surface from 4 curves but each time UV are difference.


In the Dir command, you can select the option SwapUV.

Thanks a lot dear menno :smile:
Is it any difference between set UV before create surface and change UV after create surface ?

Hi Shayan- the natural normal of the surface will change according to the ‘right hand rule’ so that it matches, in a way, the X,Y, and Z axes of a Rhino CPlane- that is if U (red, X-like) is to the right and V (green, Y-like) is away then the natural normal will correspond, in that analogy, to the +Z direction of the same arrangement of x and y on the CPlane. If you see what I mean. This seldom matters, but it might be good to know.


1 Like

Yes, there is a subtle difference in the normal direction. When you swap u and v, the normal definition of the nurbs surface changes, like Pascal says.
But you will see that the normal stays the same for the surface in Rhino, because it gets flipped independently of the surface definition. If you look closely in the Dir command you will see a small purple line at the bottom of the normal arrow. If you see this, it means that the normal of what you see in Rhino has been flipped wrt the normal of the nurbs surface definition.

1 Like

Hi dear Pascal and menno for your attention and very useful answer :smile:

How can i specify my surface (U V N) direction before creating it? because I don’t want to use from dir command.