You can edit the materials assigned to objects with the "Edit surface mapping" command. Changing texture scale, angling, translation, symmetry taking arrangements can be followed simultaneously from the perspective screen.
Click the edit surface mapping command and click the surface of the object whose material you want to edit.
The projection parameters dialog will open. Enter 90 in the angle and click the OK button.
The material texture will be rotated 90°.
Before the edit surface mapping command:
After the edit surface mapping command: