# UV points and coordinate Systems

hello,
I am trying to figure out how to determine the location of points from each other using either a UV system or a coordinate system. the problem seems to be that I dont have no way of knowing the orign (0,0) of a surface that I create with any regularity? is it supposed to be at its origin? If i create a rectangular surface for example, and have 4 points on it. How do I determine what is X and what is Y, U or V? or even how do I determine where the origin UV=0,0? See below.

So I thought about using coordinate systems, bu the problem with those seems to be that I need to make all of the axes align along lines, but I dont know how that would be possible. If I use the coordiante system by plane that seems to work good in that the red axis (which I am assuming is Z? always seems to point straight up. But is that the way it is in all cases? However, the Blue axis seems to be normal to the line which is good but sometimes it is reversed on the same line. The green axis, siimilarly is sometimes reversed. Is there a way to get them all aligned and pointing the same way? Can I somehow use a vector along the polycurves, and the XY plane to straighten them out somehow?

Did you try to check the normals of the surfaces? So maybe you can find out the origin of the UV with the normals.

Depends on how you create the surface.
Notice my example below, if I create the surface in clockwork direction the normal of the surface is 0,0,-1
When list of points reversed - the normal is in Z positive direction

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The U and V vectors are also dependent on how you create the surface as well. Rebuilding geometry often helps.

Although 99% of the time the actual directions are irrelevant if you keep things relative to the common base.

Ok I am having trouble even figuring out where the UV points actually are to help me visualize my problem. If I deconstruct a list of 4 points to UV points and then try to piece one of them back together again I dont get the original point. I think this surface point at parameter node doesnt work? What the heck am I doing wrong? Shouldn’t it return the original xyz point doing it this way? How do i make this surface point at a parameter node work with my L4 sublists if at all? Please see below.