I was investigating how to Display the Vector normals of a surface. Attached is my clustered Vector Display for a brep, but I had another thought as I was thinking about vectors - how might you retrieve the normal direction of the points from a circle?
You just need a vector. Why do you need the frame if the goal is to make a normal vector? If you want to rotate the frame then there are many rotation components. If you want to flip the plane there is a flip plane component. But again, if you just need a vector then you just need to get the planes x vectors and reverse them.
Curvature tends to flip along the curve based on curve direction (concave / convex), for a circle it is fine.
Derivatives works in the case of a circle but not a free form curve for normal, in this case it works.
See here some comparison where: Perp Frames (Green) will go all inward or all outward because they are zero-twisting). Curvature (Blue) is sometimes in the other direction based on curvature concavity or convexity. Derivatives (Red with labels) won’t find this normal.
I suppose this exercise helped me do this in 3D on a surface, this was something I tried (kind of works). I’m sure there is a better way to do this - or control object’s rotation based on it’s normals vs. the normals from the points.