Table 1: Comparison of OpenGL frame buffer mechanisms.
Conceptually, GLR render intervals are yet another mechanism for OpenGL rendering to a frame buffer. Table 1 compares key features of currently available OpenGL frame buffer mechanisms. OpenGL pixel buffers (or pbuffers) [12] exist as an experimental GLX extension implemented by Silicon Graphics for rendering into hardware accelerated, off-screen frame buffer memory.
The frame buffer state of a volatile pbuffer may be revoked at any time (inconvenient for applications). The frame buffer state of a non-volatile pbuffer is maintained always (expensive to implement and undermines sharing by multiple applications). A non-volatile pbuffer is like a render interval with an infinite timeout; a volatile pbuffer is like a render interval with a zero timeout. Render intervals represent a compromise between complete volatility of frame buffer state and total non-volatility.