The compositing preferences property editor allows you to set various preferences relating to caching, rendering performance, and Cineon/DPX image conversion. You can also set preferences relating to 2D raster paint, which are described in Raster Paint Overview.
The options on the Performance tab of the Compositing Preferences property editor help you to optimize compositing performance. Most of these preferences are used to control RAM and disk caching of operators rendered in the Fx viewer.
By default, the FxTree tries to cache all rendered frames, first to RAM and then to disk, in order to keep playback delays to a minimum. Frames are cached when you paint on an operator or edit its properties, requiring that the operator's effect be reprocessed. A most-recently-used priority list is used to control which operators are currently cached.
If necessary, you can give a particular operator a higher caching priority than other operators by activating that operator's live caching option. This is useful for render-intensive operators and operators with render-intensive parents. For more information about activating live caching, see Using Live Caching.
FxTree rendering can take advantage of multiple CPUs. You can set the Maximum Multi-Processing preference to specify the maximum number of render slave CPUs used to render FxTrees. You can specify one, two, four, or eight CPUs.
The Memory Usage options control how system RAM is used for caching FxTree images. You can set these two preferences:
The Disk Usage allow you to activate and manage a disk cache for images from Fx operators. When activated, the disk cache is used to store overflow from the RAM cache. You can set the following options:
Overflow Cache to Disk saves to a disk cache images that would otherwise be lost due to insufficient cache memory during editing of an FxTree.
Maximum Disk Cache Size specifies the maximum size of the data stored in the cache directory on disk.
Minimum Disk Left Unused specifies the amount of disk space that must remain free. This helps prevent the disk from filling up with cached images.
Cineon/DPX images use a logarithmic color space, so to work with them in the FxTree, you first have to convert them to linear space. Once you've applied the desired effects, you will probably want to convert them back to logarithmic space.
The Cineon/DPX preferences allow you to configure the logarithmic to linear lookup table, and specify when it should be used. You can have Softimage convert your Cineon files to linear color space when they are read from the FxTree and convert them back when they are written to disk.
You can configure the lookup table used for converting Cineon images between logarithmic and linear color space by setting the following Log-to-Lin Lookup Table options:
Black Point is the "Black Reference". This value maps the minimum log value to the linear black value of 0. Values below this are clipped to black.
White Point is the "White Reference". This value maps the maximum log value to the linear white value of 255. Values above this one are clipped to white.
Soft Clip helps smooth out color imbalances caused by clipping the highlights in the original log image. It defines a range of values around the white reference over which the clipping curve is softened. This helps to preserve details in the image's highlights.
Display Gamma performs a gamma correction. Entering your monitor's gamma correction value ensures that the original Cineon/DPX image's gamma looks correct on your monitor.
You can set the Fx viewer's lookup table from the Fx Viewer Settings dialog box, which you can open by choosing View 
Viewer Preferences from the Fx viewer menu.
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