Cycles Tiling and OpenEXR Cache

Overview

When rendering high resolution images with many render passes, memory usage of the render buffer can become problematic. For this reason there is a mechanism to render the image in tiles, and write each tile to an OpenEXR cache file on disk as it is finished. Only at the end of rendering do we read back the full render buffer for all view layer, and perform denoising over the full resolution buffer if needed.

Note that this tiling mechanism is different than the tiling used for GPU scheduling. An OpenEXR tile is relatively large, but not too large to fit in device memory at once. A GPU scheduling tile can be small and is used for incrementally scheduling more paths to be rendered to keep the GPU occupied. Small tiles in GPU scheduling can also help improve coherence, by rendering nearby pixels on the same multiprocessor.

OpenEXR Cache File

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Pause / Resume

TODO

Denoising

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Overlap

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