Please can some one tell me as to how do we disable rendering to screen in OpenGL.
In general OpenGL is designed to render into a window and the pixel owner ship test will discard any fragments that are not visible.
However depending on the underlying OpenGL implementation there are ways to acomplish offscreen rendering.
You may find this link usefull:
Its a tad older but still true, the only thing that changed is that pbuffers are commonly available on current mainstream hardware and not only on SGI hardware.