如何在设备之间实时同步Unity物理？ （适用于Unity的Google Play游戏插件）

Question

I'm working on real-time multiplayer game in Unity. Connection between two players is established with Google Play Game Services.
Simple example of action - shooting from a slingshot: player pulls rubber with his finger and makes shot. The only important initial data is position of rubber before player will release it, so its coordinates are sent on other device. After this projectile gets velocity ( RigidBody2D.velocity = new Vector2(...) ) and flies.

Problem is having the same initial data and executing the same code projectile can hit the target on one device and miss on other.

Answer 1

Unity's physics engine is not finite state engine and may simulate differently in different devices. But, still I used this in a simple manner for a physics based 2d game and worked out pretty well. Here's the steps that I followed:
1. Before each move, I made sure every physics objects are in same place over the networked devices.
2. Added force to the player object in the local player. Then sent the force position and direction over network to other devices. Then simulated on other devices according to it.
3. After the move is complete(on other words, all the rigidbodies are stopped), double checked if the positions, rotations are same on all devices. If not, aligned them according to the local player who made the move.

Repeated the above steps. The 3rd step is just to be 100% sure that all objects are in sync in all the devices, before I take the next move.