godxkey / unity-deterministic-physics-1

Implementing GGPO with Kimbatt's deterministic Unity physics.

Unity deterministic physics

This is a modified version of Unity DOTS Physics version 0.6.0-preview.3, which supports cross-platform deterministic physics simulation by using soft floats.

Usage

The following packages must be installed:

• Burst
• Collections
• Entities
• Jobs

You'll need to use the UnityS.Physics and the UnityS.Mathematics namespaces instead of the usual Unity.Physics and Unity.Mathematics.

See Unity Physics manual for documentation.

Notes on determinism

For a deterministic physics simulation:

• All bodies must be created in the same order every time you create the simulation
• Bodies must only be modified in a system that is updated in FixedStepSimulationSystemGroup
• You must not use the result of floating point operations as input for the physics engine
• Be careful when using hashmaps / hashsets, because iterating over them may be non-deterministic (it depends on the implementation).
• Check how to use soft floats here.
• Make sure that your code is also deterministic.

Example

See the ExampleScene scene for an example. After running it, your simulation should look exactly like this:

License

Unity.Physics, Unity.Mathematics, and Unity.Transforms are licensed under the Unity Companion License.

Soft floats is licensed under the MIT License. See https://github.com/Kimbatt/soft-float-starter-pack for more information.