10. Clicking on the ‘Direction’ button then selecting a NURBS surface will show us several things about it. White arrows will give a ‘facing direction’,and if we place the cursor over the surface two small arrows, one green and one red, will indicate the orientation of the U and V coordinates of the surface. Here we are examining the wing surface and we can see the red arrow points from tip to root, while the green arrow points forwards to the leading edge. Doing the same examination of the original rectangle used to make our mesh, the red arrow points towards the 1 unit edge, while the green arrow points to the 10 unit edge.
Notice we are looking at the NURBS surfaces, and NOT the mesh made from these surfaces. The UV directions are inherited by the meshes produced, but Rhino cannot display these on a mesh object.
However, when a mesh is applied to a NURBS surface the UV directions are aligned. Therefore we need to somehow change the direction of either the wing surface or the surface making the mesh so that both red arrows point the way we want, and the mesh gets applied in the right direction.