Surface point at parameter results wrong location


As shown in this image a UV values of 0,0 create a point at the right of the surface i would expect it to return the point on the left most side. This seems dependent on how the lines were drawn in Revit.
How can i control or find the furthest x point, y point
My goal is to create a grid of a fixed size starting at the left most point and stopping at the right most point.
im not trying to fill a surface with quads

It’s exactly as you assumed. The UV parameters are dependent on the surface orientation. In order to find the leftmost (and I assume bottommost) points you just need to filter the X and Y (and potentially Z) coordinates of each point.

You could also get the local coordinate system of the surface and use that to know whether to draw your grid left to right or right to left.

can you point me to how to extract the coordinate system from the surface

Sorry, I thought Geometry.ContextCoordinateSystem would read the local CS of the surface but it just reads the CS used to build the geometry. You could still compare the first and last points in the UV array though to see the direction it’s going, or, like I originally said, just filter for minimum coordinates.