I’m developing a coop game that is on Listen Server and I want to add a vehicle that is possessed by the driver that has steering wheel controls and a passenger that has throttle and brake controls.
I currently have the driver that has all the controls assigned on him (He possesses the vehicle) and my passenger can enter the vehicle but can’t control the throttle and brake.
I have a IMC_Steering Wheel and IMC_Throttle_and_Break in 2 different Input Mapping Contexts.
How would I be able my passenger to control the throttle and brake WITHOUT possessing the vehicle?
Passenger has his own player controller (PC), so you could manage it through it →
PC receives input locally, PC calls server function on itself (like ServerBrake) and then server calls Brake on a vehicle that this PC uses (you should store vehicle as a separate variable, since passenger is not possessing that vehicle).
So I changed it up a bit and added this to my code. I have a collision box in the passenger seat and when I press “E” key, I can sit on the seat and I trigger an “Add Mapping Context” function that switches my default IMC to the Vehicle’s IMC.
Basically, whenever I get into the vehicle and press “W”, it appears that the Input Action event below there is working. I get “1.0” Float value when pressing it and when I stop pressing it I get “0.0”.
The problem is the car doesn’t move anywhere, I can’t control it still.
In this setup you will end up having replication problems with the passenger.
Player 1 possess the vehicle, which means that it is an Autonomous Proxy on Client 1
Player 2 needs to control the vehicle’s throttle so you would need to command a Simulated Proxy on Client 2 which is impossible to do directly. (It is also impossible to possess the vehicle from two different controllers.)
The way I see it (keep in mind I’ve never tried something like this) is as follows:
Player 1 possess the vehicle as you are currently doing it.
Player 2 sends RPCs either directly from the controller or some invisible pawn.
(Ignore for now that player 2 doesn’t move with the vehicle)
Make the server event update the vehicle’s throttle.
This will most likely produce errors on Client 1 as it assumes that Player 1 is the sole controller of the possessed pawn, in which case just make Player 1 posses another invisible pawn like Player 2 does. It might be necessary to posses the vehicle with an AI controller to work. In this case, the AI is actually possesses the vehicle but the players posses a “remote control pawn” that would give it commands.
This is a really ad hoc solution - it might work but if you want it done for production, you will really have to modify core systems like replication, network predictions and movement controllers.
So I’ve tried doing something different than the one before. The code below is inside the “BP_Player1” (which is a copy of BP_ThirdPersonCharacter). Basically I tried to make a “Blueprint Interface” as you can see and I tried carrying the Action Value Float data between classes with it. According to the codes below, I managed to get the Action value working. Like, whenever I press “W” key, it prints the value as “1.0” and whenever I lift, it goes back to “0.0”. The thing that I’m struggling is I can’t trigger the “Set Throttle Input” function. Any ideas you have on this matter would be very useful. Thanks!
