Question Predicted Physics + Predicted Player Spawned Objects Not Spawning In the Right Location

ISSUE: For some reason the client-spawned bullets are spawned in the "wrong place" and then their position corrects

- I have a predicted Player object and am running predicted physics
- The client can use wasd to generate ICommandData
- The Player object can spawn bullets by hitting space bar (will be ICommandData shoot = 1)
- The bullet is spawned at an offset location at the end of the player's "gun"
- InputSystem takes in wasd commands and generates ICommandData
- InputResponseMovementSystem reads commands and adjusts PhysicsVelocity.Linear and runs before BuildPhysicsWorld
- InputResponseSpawnSystem
- reads commands and creates the bullet
- and gives it a PhysicsVelocity of whatever the player is + the forwards direction
- runs after ExportPhysicsWorld
- records commands onto BeginSimulationEntityCommandBufferSystem

Here are the systems for the client:


Here are the systems in server


For some reason the client spawns the bullets "off" then they are "fixed" to where they should be. I assume this has to do with the server "correcting" what the client thought? It is exacerbated by a high velocity.

See video of the bullets being "wrong" then being updated:

If the client is predicting physics, and it is "correct" because it is not interacting with anything, why would the bullet not spawn in the correct location?

When the player is not moving or moving very slowly this issue is not noticeable, it is when my player is moving quickly laterally. It is like the client is spawning the bullet where the player was? Or is it something else?

 

Shoot I ripped off your asteroids approach, I will double check to make sure I did not mis-implement and report back.

 

For some reason now the predicted physics system are in the fixed step simulation group



I have not changed the code to create the physics singleton.

Code (CSharp):

1.         Entity physicsSingleton = EntityManager.CreateEntity();
2.         EntityManager.AddComponentData(physicsSingleton, new PredictedPhysicsConfig {});

Why did this occur?

 

• I was on my mac and it was working as expected, systems were moved to PredictedPhysicsSystemGroup
  
• I pushed my updates to github and then pulled and loaded the project on Windows
  
• Now on windows (no changes) the systems are no longer in the GhostPredictionSystemGroup

 

Yes, it existed in both server and client worlds.

Changing to be put in FixedStepSimulationGroup instead of PredictedPhysicsSystem group fixed the issue.

Maybe there was some race condition in the windows that didn't exist in mac? Regardless, it is fixed and working again now thank you.

 

I realize I did not understand this as much as I did.

How can I prevent spawn logic for a rollback? I am assuming that is why the bullets are appearing where I was a few frames ago?

 

The same problem seems to exist in the Asteroids example. The position of the player when receiving input (InputSystem) and when processing input and spawning bullets (SteeringSystem) do not match. (on client)

In the example (SteeringSystem.cs), I moved the line

position.Value.xy += Velocity.Value * deltaTime;

below input handling

if (inputData.shoot != 0 && canShoot) { ... }

for correct comparison.

attached Asteriods example and one more my example screenshots.