In a "multitouch" environement, any application showed on a surface can be rotated/scaled to the direction of an user. Actual solution is to drawing the application on a FBO, and draw a rotated/scaled rectangle with the texture on it. I don't think it's good for performance, and all graphics cards don't provide FBO.
The idea is to clip the rendering viewport in the direction of user.
Since glViewport cannot be used for that, is another way exist to achieve that ?
(glViewport use (x, y, width, height), and i would like (x, y, width, height, rotation from center?))
PS: rotating the modelview or projection matrix will not help, i would like to "rotate the clipping plan" generated by glViewport. (only part of the all scene).
If you already have the code set up to render your scene, try adding a glRotate() call to the viewmodel matrix setup, to "rotate the camera" before rendering the scene.
Rotating a glViewport?