Frame Buffers




Frame Buffer Files

mental ray is able to temporarily store frame buffers in frame buffer files on disk instead of keeping them in memory during rendering, given that sufficient disk space is available. This allows to use very large frame buffers, or very large numbers of frame buffers, without being limited by available physical memory. This feature can be controlled on the mental ray command line. By default, this disk cache mechanism is using memory mapping techniques for performance reasons, which requires that the frame buffers fully fit into the virtual memory address space of the process.

The frame buffer cache, on the other hand, stores only fragments of frame buffers in the disk files on demand. This feature may save significant amount of memory when rendering very high resolution images, and is especially useful on 32bit systems with limited memory resources. If enabled, only a small fraction of each frame buffer is present in memory, like the currently rendered tile, and tiles recently accessed in mental ray by the display callbacks, output shaders, or when writing final images to files. This technique is typically superior to memory mapped frame buffers which need to be stored and restored as a whole, hence more appropriate when rendering many but smaller frame buffers.


Frame buffer files are stored in the directory specified with the -fb_dircommand line option; or in the directory specified in the TMPDIR or TEMP environment variables.

Frame buffer files are removed from disk when rendering has finished.

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