The particle startup cache lets you save files at frames greater than the start frame without doing a run-up. It saves a copy of the particle shape’s attribute values in a different file than the particle disk cache files.
Using the startup cache lets you save and quickly re-load scenes at frames greater than the start frames of your particle objects. If you always save your files at the particles’ start frames, you can turn off Save Startup Cache for Particles to save disk space.
The disk space used for the particle cache is determined by how many particles are in your scene at the frame saved, and how many attributes they have. Likewise, the time savings at file load is determined by how heavy your scene is and how long it takes to play back. There is no simple formula—you must assess the trade-off between file size and time savings. Because of this, we made this a preference you can turn on or off. It is turned on by default.
When this option is turned on (the default), Maya automatically saves the startup cache for all your particles every time you save the file. Unlike particle disk caches, you don’t have to create the startup cache explicitly every time.
When the file is loaded (in either interactive or batch mode), the particle shape’s current state is read from the startup cache and no run-up occurs. If Maya cannot find or read the cache file, it gives you a warning and then runs the scene up. This would happen, for example, if you copied the file into a different workspace and did not also copy the startup cache. If you re-save the scene at that point, Maya re-creates the startup cache.
Location and names of startup cache files
Startup cache files are kept in a subdirectory of your workspace particles directory. Each scene has a separate startup cache directory.
Normally, Maya names this directory by appending _startup to your scene name. For example, if your scene is called myScene, Maya puts the startup cache in a directory called myScene_startup.
However, if you have created a particle disk cache for that scene, Maya uses the name of that particle disk cache directory in place of your scene name. For example, if you store your particle disk cache in a directory safePlace, Maya calls the startup cache safePlace_startup. (By default, the disk cache directory name is the same as the scene name.)
If you first disk cache the scene under one name, then rename the scene, any startup file written uses the first name (because that’s the name your disk cache was created under). We recommend that you name your scene when you start and don’t change it.
Using startup caches with batch rendering
Maya uses the startup cache in batch rendering only when you are rendering the exact frame for which the startup cache was saved. It does not use the startup cache when you are rendering other frames. When rendering sequences, or rendering in distributed or multiprocessor fashion, we recommend that you use the particle disk cache and not rely on the startup cache.
Using disk caches and startup caches
If you have both a particle disk cache (a complete sequence) and a startup cache, the particle disk cache takes precedence. Maya searches for caches in the following order:
If you have a particle disk cache, but you want to save a state that is different from what’s stored in the particle disk cache, be sure to turn off Use Particle Disk Cache before saving the file. Otherwise, Maya saves what was in the disk cache, using that cache until you specify not to use it.
