A set of options that control how physics operates when using the job system to multithread the physics simulation.
Multithreaded physics is currently an experimental feature. As such, many options are exposed that allow performance configuration that may not be available when the feature moves out of experimental status.
A physics simulation executes in the following discrete stages:
• Find New Contacts
• Contact Collision
• Discrete Solver (Clear Island Flags -> Discrete Island Traversal -> Discrete Island Solver -> Synchronize Fixtures -> Find New Contacts)
• Continuous Solver (Clear Island Flags > Continuous Island Traversal -> Discrete Island Solver -> Synchronize Fixtures -> Find New Contacts)
• Clear Body Forces
• Update Trigger Contacts
These stages execute in the order given above. Each stage is run as a job "task". Each task executes sub job tasks, which are shown in parenthesis above. When executing a job, physics simulation may process bodies, contacts, joints, and so on, across multiple job threads. You can task each of these threads with executing a specific number of items, such as bodies, contacts and joints. Many of the options provided here allow you to control the minimum number of items assigned to each job. Raising the minimum can reduce the number of jobs required. This is because running a lot of jobs, each processing only a few items, is usually not very efficient. The default settings provide a decent performance to job balance, however you are free to experiment.
Additionally, prior to the simulation being run, Rigidbody2D interpolation/extrapolation poses are stored ready for per-frame interpolation/extrapolation. These are also executed using the job system and are controlled here.