I wonder whether there is a way to align the active camera axis with an edge. I need this to be able to rotate an object around an arbitrary axis and it seems to me that the only way to achieve this requires that particular axis (in this case, the edge) to be perpendicular to the camera view, thus parallel to/aligned with the camera axis. Thanks.
There would be a number of ways of doing this. If you want the camera on the edge with its local axes along the edge then one way is:
Select the edge
Position the curser on the edge (Shift+S / curser to selected)
Align the view to the edge, Shift+Numpad 1 (or View / Align View / Align View to Selected)
Align Camera to view, Ctrl+Alt+Numpad 0 (or View / Align View / Align Active Camera to View)
Move the camera to the curser (Shift+S / Selected to curser)
Change the transform orientation to Local
If you just want a custom axis you can select the edge and Ctrl+Alt+Spacebar to create a custom orientation that you can use to rotate the camera
Thanks, it was easier that I had expected: Edit Mode; Wireframe; Create edge (edge is now selected); View Orthogonal; Align View / Align View to Selected / Top (edge is now the axis of rotation for what follows); Object Mode; Select object to rotate, if not already selectedr; Object / Transform / Rotate.
Being a new forum user I cannot immediately edit my posts, so here goes. There is one step missing in my sequence posted above – right before the rotation is to be performed the pivot must be moved to the 3D cursor.
I give up posting here, I cannot edit my posts. Thanks for your help.