Dynamics preferences

Dynamics

Auto create rigid body: Turn this option on to automatically create active rigid bodies when you connect an object to a field (apply a field’s influence to geometry).
Run up to current time: If you click a frame in the Time Slider, the correct state of all dynamic objects in the scene is displayed only if Maya performs run-up to calculate each frame prior to that frame. Turn this option on if you want to click frames in the Time Slider. Note that run-up also occurs for hidden objects.

Leave run-up turned off if you want to prevent Maya from calculating dynamics when you click in the Time Slider. This is useful in a scene that has both nondynamic objects and complex dynamic objects, where you want the state of nondynamic objects to appear promptly after you click the Time Slider. If you are keying dynamic objects, it’s also useful leave run-up turned off to avoid waiting for run-up calculations that are irrelevant to your keying activities.

Run up from

Select one of the following options:

Previous Time: If you click a frame higher than the current frame, run-up starts from the prior current time and ends at the frame you click. Select this option if you won’t be changing any attributes of a dynamic object in the scene. This setting lessens the time you’ll spend waiting for run-up. If you click a frame lower than the current frame, run-up starts from the beginning of the animation.
Start Time: Run-up starts from the start frame regardless of where you click in the Time Slider. Select this option if you plan to change any attributes of a dynamic object in the scene. This ensures that you see the correct object states when you click in the Time Slider after modifying an object’s dynamics.

Save startup cache for particles: When this option is turned on (the default), Maya automatically saves the start-up cache for all your particles every time you save the file. Unlike particle disk caches, you don't have to create the start-up cache explicitly every time. See Dynamics for more information.
Echo collision commands: When you have a particle collision MEL callback specified, every time a collision happens, Maya echoes the command that it is running, then runs it. In a scene with thousands of particles, that produces a great deal of unnecessary output to the Script Editor. This preference enables and disables echoing of the collision commands before they are run.