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During rendering, whenever 3Delight encounters a non-optimized texture, it will create an optimized copy automatically. The optimized texture will be saved at the same location and will have the same base name as the associated non-optimized texture, but with a .tdl extension added. This process will skip any texture that have the .tdl substring in the file name (e.g. texname.tdl.tif and texname.tif.tdl (as they will be considered as already optimized). Note that 3Delight also detects if a source texture has changed since the optimize optimized copy and will automatically re-optimize it.
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Another consideration is if you don't like the delay that will occur at the start of a render the first time one or more textures are used. And instead you prefer handle handling that one time optimization process manually and on your own term.
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