The character in this sample is fairly complex. Due to its level of complexity, we've decided to separate its movement logic into various "states".
The implementation of the character logic resembles the third-person standard character at its core, but PlatformerCharacterAspect.PhysicsUpdate and PlatformerCharacterAspect.VariableUpdate is where it starts to differ. PlatformerCharacterAspect.PhysicsUpdate starts by handling logic that is common to all states, then calls the current state's physics update via stateMachine.OnStatePhysicsUpdate, and finally does more logic common to all states after the state machine update. Similarly, PlatformerCharacterAspect.VariableUpdate calls the current state's variable update via stateMachine.OnStateVariableUpdate.
In short; instead of having all character update logic in the PlatformerCharacterAspect directly, we've implemented the logic of each state in their own struct. PlatformerCharacterStateMachine is responsible for calling the state update methods on the current state struct. For each state method, we pass the PlatformerCharacterAspect by reference, along with the character update contexts, so that state updates can have access to all the data they need.
Every character state checks for state transitions, typically at the end of their OnStatePhysicsUpdate. When they determine that they should transition, they call stateMachine.TransitionToState.
Here are the various states of the character:
- Ground Move
- Air Move
- Crouched
- Wall Run
- Flying
- Dashing
- Rope Swing
- Rolling
- Swimming
- Climbing
- Ledge Grab
Here is a quick description of how several other features were implemented:
Planet Gravity: The gravity of all physics objects in this sample is handled by a CustomGravity component, a GravityZonesSystem, and special gravity zones such as GlobalGravityZone and SphericalGravityZone. The GravityZonesSystem will handle calculating a spherical gravity for all CustomGravity entities in its sphere trigger zone. Then, it will apply a global gravity to all CustomGravity entities that are not in any other kind of gravity zone. Finally, for all dynamic body entities that have a CustomGravity and a PhysicsVelocity, it will add that calculated gravity to the PhysicsVelocity.Linear. The character doesn't get its velocity modified even though it has a CustomGravity, because it is not a dynamic body. The character takes care of adding its custom gravity to its KinematicCharacterBody.RelativeVelocity in its state updates. And finally, the character orients its rotation so that it always points towards the opposite of the custom gravity's direction.
Ice Surface: A CharacterFrictionModifier component can be placed on rigidbodies to modify the character's simulated friction when it walks on that surface. In its state movement updates, the character tries to see if the ground hit entity has a CharacterFrictionModifier component, and if so, it'll change the way it controls its velocity based on the CharacterFrictionModifier.Friction
Wind Zone: A WindZoneSystem iterates on all entities that have a WindZone component and a trigger collider that raises trigger events. For each teleporter, if a trigger event with a KinematicCharacterBody was detected, we add a wind acceleration to the KinematicCharacterBody.RelativeVelocity
Jump Pad: A JumpPadSystem iterates on all entities that have a JumpPad component and a trigger collider that raises trigger events. For each teleporter, if a trigger event with a character was detected, we unground the character and add a velocity impulse to the KinematicCharacterBody.RelativeVelocity
Teleporter: A TeleporterSystem iterates on all entities that have a Teleporter component and a trigger collider that raises trigger events. For each teleporter, if a trigger event with a KinematicCharacterBody was detected, we move the character position to the teleportation destination point. Additionally, since we don't want character interpolation to be active for the teleportation, we call SkipNextInterpolation() on the CharacterInterpolation component of the character entity. This will skip the interpolation for the remainder of the frames until next fixed update.
Sticky Surfaces (walk on walls): PlatformerCharacterComponent.StickySurfaceTag allows us to assign a physics tag that represents sticky surfaces that the character can walk on. In the character's state update, it will see if the rigidbody of the ground hit entity has that tag, and if so, it will orient its rotation so that it always points towards the ground normal. Moreover, since the character's GroundingUp is always set to be the character rotation's up direction, our grounding reference direction will always be relative to the character orientation, which means the character could consider itself grounded even if it was standing upside down on the ceiling.