normals and rotations


short question:

If I have a normal in a certain vertex, and then rotate the vertex, do I have to rotate the normal too??
I mean physically rotate it in 3D-space with sin and so on. Like rotating around Z-Axis 90°. From my point of view I don’t have to rotate the normal since it is situated perpendicular to a vertex, right??

I’m a little confused about this topic since the last discussion with a colleague.



The normal should be rotated with the object. If you rotate your object with OpenGL’s own matrix functions, the normal will automatically be rotated.

Thanks Bob for solving this mysterie!