Auto-Disable area
The Auto-Disable area contains settings for creation of thresholds beyond which the Physics Solver will cease to solve. This lets you save system resources by disallowing solving behavior that is no longer visible.
Enable
You can activate or disable every simulated object. When you disable an object, it no longer participates in the simulation, and is not updated. You can only perform Collision detection with two enabled objects, or an enabled object and a disabled object.
When you activate auto-disabling, any object that comes to rest is then disabled. This is also used manage key amounts; when you disable an object, keys are no longer added to FCurves.
Linear Threshold
Lets you set a linear velocity limit for disabling an object. When you specify a Linear Threshold value, you create a limit so that when the Linear Velocity goes below this clamp, it is disabled.
Angular Threshold
Lets you set an angular velocity limit for disabling an object. Once the Angular velocity goes below a specific value, it clamps and disables the object.
Steps
Lets you set the number of simulation steps that an object requires to be idle before it is disabled. Set a value for how many steps the action performs before the object is considered dropped. The lower the number, the faster it becomes inactive.
Reset to Default
Click this button to reset all the settings to their default values.