With meshes we have .PointAt() and .NormalAt() methods.
What about SubDs?
Can we extract, say, a point in a face giving it the face index and the vertexes coordinate?

And the opposite.
Intersecting a ray to a SubD, can’t we get a “SubD parameter”?

I’m more interested on the first part tought.
Any workaround much appreciated…

That’s… not “evaluating”.
I need to work by code, starting from vertexes and following some logic extracting points and normals around each vertex, but by followin the face-edge topology (like in meshes).

Also the brep structure is way heavier.
I hope that extracting point+normal of a subd is faster.

hmm, yes I see
if you treat the subd as mesh it will take the control mesh and gives weird results.
you might take the approximated (render)mesh then, not sure if that helps in your case?

This post is not about grasshopper.
I mean, i will use it inside grasshopper… … but the question is about managing SubDs in rhinocommon/c# .

Yes, using the rendermesh would be good, because the mesh vertexes lie on the subd surface and normals are decent, but i would still need some relationship between the SubD topology and the rendermesh topology.
And also, GH have that “Mesh from SubD”, but rhinocommon not.

I would ask Dale Lear … but i remember he retired…

@maje90 Yes, the render mesh faces are ordered in a manner that makes it quite easy to find the correlation between SubD faces and the mesh faces. Let me know if you need help.