Snapshot: A rapid technique for driving a selective global illumination renderer

Even with modern graphics hardware, it is still not possible to achieve high fidelity global illumination renderings of complex scenes in real time. However, as these images are produced for human observers, we may exploit the fact that not everything is perceived when viewing the scene with our eyes. We are drawn to certain salient areas of an image. Taking this into account, it is possible to selectively render parts of an image at high quality and the rest of the scene at lower quality without the user being aware of this difference. Methods exist for calculating which parts of an image are perceptually important, but generally they rely on having a fully rendered image to process. It is thus only possible to prioritise pixels to speed up the rendering of a frame once that frame has been rendered: an obvious catch. In pre-scripted animated sequences it is indeed possible to use rendered key frames to extract the necessary information, however, the cost of rendering such key frames could be significant and this is not appropriate for any interactive application. This paper presents a high speed OpenGL generated ""Snapshot"" of a frame to generate a saliency map to efficiently drive the selective global illumination rendering of an animated sequence.