Here is a video of what I’d like the final solution to act like. Currently, it is my game running in standalone mode: Standalone Example - YouTube
Here is a video of my game running as a client: Client Example - YouTube
The difference should be clear - there is substantial jitter in the second, client based, video. Any moderate distance away from the projectile and it is jittering so bad that it blurs. My question is, how do I get rid of the jitter? I believe it’s a networking and replication issue. Below is an explanation of how things are wired up - I’ll show blueprints for the relevant parts.
The shot is initially fired by the client, which calculates the spawn location and forward vector and then makes a call to a server-only event. The server spawns the actor, which then calls an interface function on the spawned actor, Set Forward Direction. Here’s a picture.
Set Forward Direction is implemented no the projectile actor and really doesn’t do much aside from set a “RepNotify” variable called forwardVector. Here’s a picture.
The forwardVector variable’s replication condition is set to “Skip Owner”; however, since I don’t set the owner of the actor all clients and the server have their OnRep function get called. The OnRep function for the forwardVector variable sets the velocity for the projectile - here’s a picture.
The projectile actor, the one that is spawned, has the following components: ProjectileMovement, and a collision sphere that has the following 3 child components: the mesh, smoke, and an explosion effect. The actor’s replication settings can be seen here.
The ProjectileMovement component on the projectile actor has the following configuration:
- Under Component Replication, the Component Replicates box IS NOT checked.
- The initial velocity is set to (0,0,0)
- Projectile Gravity Scale is set to 0.0
- In Projectile Interpolation, Interp Movement is checked, but everything else is left default. See here.
Another critical piece to this puzzle (I think…) is how I set the interpolated component and the updated component. I do this in the Construction Script for the projectile actor. See here.
I have tried tinkering with the interp parameters in the Projectile Interpolation section, but I haven’t really seen that much of a noticeable difference. I was looking at the documentation for the Projectile Interpolation settings (Projectile Movement | Unreal Engine Documentation and Interpolation | Unreal Engine Documentation) and my only thought is that my extending the Actor class and overwriting the PostNetReceiveLocationAndRotation function to call MoveInterpolationTarget, but I was hoping that how I had things setup in the Construction Script on my projectile actor that this was happening already. Is this not the case?
I realize I do have alternatives… For example, I could uncheck the Replicate Movement field on my projectile actor. The client would then essentially be responsible for doing their own thing, but this might be ok since the projectile is created and velocity is applied at roughly the same time on both the client and the server. Regardless, this will not work for all edge cases… For example, consider close quarters combat where a client is receiving slightly lagged updates on his opponents location… Since the server is the responsible authority for detecting the collision, the projectile on the client side could hit and then stick to the opponent even though it barely missed in the server’s calculation. Without location replication to correct for this, the projectile on the client’s view is incorrectly stuck/stopped.
Link to all BP screenshots: Server Spawns Actor - Album on Imgur
Any thoughts, help, or guidance is much appreciated 