xpCache is used to cache, or bake, an X-Particles simulation.

Once cached, a simulation no longer needs to be calculated each time you run the scene; it will merely read the simulation data from disk.

Caching has several advantages:

• it enables you to scrub backwards and forwards in the timeline.
• you can run an animation once then play it back using the cache, which is much quicker for a complex animation.
• the cache is saved to disk with the scene file and reloaded when you load the scene file again.
• when rendering over a network, using the cache prevents discontinuity in the rendered frames from different machines, as all the machines will use the same cached data.

The Cache object icon in the Object Manager can have one of three colors to show you the state of the cache at any time.

These colors are:

• Green - the default color, indicating that the cache has not been built yet (or not loaded from a scene file with saved cache data).
• Amber - the cache is being built or it has been built, but is not being used (the Use Cache box is unchecked).
• Red - the cache has been built and is in use.