Use this skill when working with character movement, CharacterMovementComponent, CMC, movement modes, walking, falling, swimming, flying, custom movement, network prediction, FSavedMove, root motion, floor detection, step-up, or character physics. Also use for 'PhysWalking', 'PhysCustom', 'LaunchCha

UE Character Movement You are an expert in Unreal Engine's UCharacterMovementComponent (CMC), the core system that drives character locomotion, floor detection, network prediction, and root motion integration. You understand the full Phys pipeline, custom movement mode implementation, and the FSavedMove Character prediction architecture. Context Check Read .agents/ue project context.md to determine: Whether the project uses ACharacter or a custom pawn with its own movement The UE version (UE 5.4+ adds GravityDirection support, UE 5.5 changes DoJump signature) Whether multiplayer is involved (affects prediction pipeline complexity) Any existing CMC subclass or custom movement modes already in use Information Gathering Ask the developer: 1. Are you extending UCharacterMovementComponent or configuring the default one? 2. Do you need custom movement modes (wall running, climbing, dashing)? 3. Is this multiplayer? If so, do custom abilities need network prediction? 4. Are you integrating root motion from animations or gameplay code? 5. Do you need custom gravity directions (UE 5.4+)? CMC Architecture UCharacterMovementComponent sits at the end of a four level class hierarchy: CMC also implements IRVOAvoidanceInterface and INetworkPredictionInterface . It is declared UCLASS(MinimalAPI) . CMC lives as a default subobject on ACharacter , created in the constructor. ACharacter provides the capsule, skeletal mesh, and high level actions ( Jump , Crouch , LaunchCharacter ), while CMC handles the actual physics simulation, floor detection, and network prediction. Movement Modes CMC dispatches movement logic through EMovementMode : Mode Value Description MOVE None 0 No movement processing MOVE Walking 1 Ground movement with floor detection and step up MOVE NavWalking 2 Walking driven by navmesh projection MOVE Falling 3 Airborne — gravity, air control, landing detection MOVE Swimming 4 Fluid movement with buoyancy MOVE Flying 5 Free 3D movement, no gravity MOVE Custom 6 User defined; dispatches to PhysCustom with a uint8 sub mode MOVE MAX 7 Sentinel value Change modes with SetMovementMode(EMovementMode, uint8 CustomMode = 0) . The CMC calls OnMovementModeChanged(PreviousMode, PreviousCustomMode) after every transition, which is the correct place to handle enter/exit logic for custom modes. Phys Movement Pipeline Every tick, CMC processes movement through a strict pipeline. Understanding this flow is essential for writing correct custom movement or debugging unexpected behavior. PerformMovement(float DeltaTime) is the main entry point (protected). It calls StartNewPhysics() , which dispatches to the appropriate Phys function based on the current EMovementMode . Each Phys function is protected virtual : PhysWalking(float deltaTime, int32 Iterations) — ground movement PhysNavWalking(float deltaTime, int32 Iterations) — navmesh projected walking PhysFalling(float deltaTime, int32 Iterations) — airborne/gravity PhysSwimming(float deltaTime, int32 Iterations) — fluid movement PhysFlying(float deltaTime, int32 Iterations) — free flight PhysCustom(float deltaTime, int32 Iterations) — your code here Inside each Phys function, two core methods do the heavy lifting: CalcVelocity computes the velocity for this frame: SafeMoveUpdatedComponent moves the capsule and resolves penetration: It wraps MoveUpdatedComponent and automatically handles depenetration if the move results in an overlap. Always prefer SafeMoveUpdatedComponent over MoveUpdatedComponent in custom Phys functions. When a sweep hits a surface, SlideAlongSurface projects movement along it. When hits occur in a corner (two blocking surfaces), CMC calls TwoWallAdjust (virtual on UMovementComponent ) to compute a safe movement direction that avoids both walls. During PhysWalking , ComputeGroundMovementDelta (virtual) adjusts the velocity delta to follow the floor slope — it projects horizontal input onto the floor plane so the character walks along inclines rather than into them. See references/movement pipeline.md for the full flow diagram and per mode breakdown. Floor Detection CMC's walking mode relies on continuous floor detection to determine whether the character is grounded. FFindFloorResult Floor Detection Methods FindFloor is the primary method: It delegates to ComputeFloorDist() , which performs a downward capsule sweep followed by a line trace. The sweep finds the floor surface, and the line trace validates walkability at the exact contact point. Walkable Floor Angle Two linked properties control what counts as "walkable": WalkableFloorAngle (default 44.765 degrees) — the maximum surface angle in degrees WalkableFloorZ — the corresponding Z component of the surface normal (auto calculated from the angle) Set the angle, not the Z value directly. SetWalkableFloorAngle() updates both. Custom Movement Modes MOVE Custom with a uint8 sub mode is the standard way to add new movement types. This gives you up to 256 custom modes while reusing CMC's full network prediction pipeline. Implementation Steps 1. Define custom mode constants: 2. Override PhysCustom in your CMC subclass: 3. Enter the mode using SetMovementMode : 4. Handle transitions in OnMovementModeChanged : Inside PhysCustom , dispatch on CustomMovementMode and implement your simulation. Call CalcVelocity for acceleration, SafeMoveUpdatedComponent for capsule movement, and SetMovementMode when transitioning out. See references/cmc extension patterns.md for a complete wall run implementation. Network Prediction CMC uses a client side prediction and server reconciliation model. The client runs movement locally, saves inputs, sends them to the server, and corrects if the server disagrees. This is why custom movement must integrate with the prediction pipeline to work in multiplayer. FSavedMove Character Each client tick generates a saved move that records the input state: Key fields: bPressedJump , bWantsToCrouch , StartLocation , StartVelocity , SavedLocation , Acceleration , MaxSpeed . Key virtuals to override for custom data: Clear() — reset your custom fields SetMoveFor(ACharacter , float, FVector const&, FNetworkPredictionData Client Character&) — capture your custom state from the CMC before the move executes PrepMoveFor(ACharacter ) — restore your custom state before replaying a move GetCompressedFlags() const — pack custom booleans into the uint8 flags CanCombineWith(const FSavedMovePtr&, ACharacter , float) — return true only if two moves are identical (enables bandwidth optimization) PostUpdate(ACharacter , EPostUpdateMode) — called after the move executes IsImportantMove(const FSavedMovePtr&) — prevent combining if this move carries significant state CompressedFlags The uint8 returned by GetCompressedFlags has a fixed layout: Flag Value Purpose FLAG JumpPressed 0x01 Jump input FLAG WantsToCrouch 0x02 Crouch input FLAG Reserved 1 0x04 Engine reserved FLAG Reserved 2 0x08 Engine reserved FLAG Custom 0 0x10 Your custom flag FLAG Custom 1 0x20 Your custom flag FLAG Custom 2 0x40 Your custom flag FLAG Custom 3 0x80 Your custom flag You get four custom bits. For more complex state, use FCharacterNetworkMoveData . FNetworkPredictionData Client Character Override AllocateNewMove() to return your custom FSavedMove subclass: The CMC exposes this via GetPredictionData Client() , which you override to lazy init your custom prediction data class. Modern Packed RPCs UE5 uses packed move RPCs on ACharacter : ServerMovePacked(FCharacterServerMovePackedBits) — client to server ClientMoveResponsePacked(FCharacterMoveResponsePackedBits) — server to client The old RPCs ( ServerMove , ServerMoveDual , ClientAdjustPosition ) are DEPRECATED CHARACTER MOVEMENT RPC . For custom network data beyond CompressedFlags, derive FCharacterNetworkMoveData (override ClientFillNetworkMoveData , Serialize ), derive FCharacterNetworkMoveDataContainer , and call SetNetworkMoveDataContainer() in your CMC constructor. See references/cmc extension patterns.md for full FSavedMove and network data implementation templates. Root Motion Root motion allows animations or gameplay code to drive character movement directly. CMC integrates root motion through FRootMotionSource and its subclasses. FRootMotionSource Base class fields: Priority — higher priority sources override lower LocalID — unique ID returned by ApplyRootMotionSource InstanceName — FName for retrieval and removal Duration — total time in seconds; negative Duration means infinite (runs until explicitly removed) AccumulateMode — Override (replaces other sources) or Additive (stacks) Subclasses Class Key Parameters Use Case FRootMotionSource ConstantForce Force , StrengthOverTime Knockback, wind FRootMotionSource RadialForce Location , Radius , Strength Explosions, vortex FRootMotionSource MoveToForce StartLocation , TargetLocation Dash to fixed point FRootMotionSource MoveToDynamicForce SetTargetLocation() Homing dash FRootMotionSource JumpForce Rotation , Distance , Height Targeted jump arc CMC Methods Apply a constant knockback: Key Properties Property Default Description MaxWalkSpeed 600 Maximum ground speed MaxAcceleration — Rate of speed change GravityScale 1.0 Multiplier on world gravity JumpZVelocity — Initial vertical velocity on jump AirControl — Lateral control while falling (0 1) GroundFriction — Friction on ground surfaces BrakingDecelerationWalking — Deceleration when no input on ground MaxStepHeight — Maximum height of obstacles to step over WalkableFloorAngle 44.765 Max walkable surface angle in degrees MaxWalkSpeedCrouched — Speed while crouching MaxSwimSpeed — Maximum speed in water MaxFlySpeed — Maximum speed when flying MaxCustomMovementSpeed — Speed cap for custom modes bOrientRotationToMovement — Rotate character toward movement direction bUseControllerDesiredRotation — Smoothly rotate toward controller rotation NetworkSmoothingMode — Simulated proxy interpolation mode MaxSimulationTimeStep — Cap on sub step delta for stability MaxSimulationIterations — Max physics iterations per frame bUseRVOAvoidance false Enable RVO (reciprocal velocity obstacle) avoidance AvoidanceGroup — FNavAvoidanceMask — group membership for avoidance filtering AvoidanceWeight — float — higher weight yields right of way to other agents Rotation bOrientRotationToMovement and bUseControllerDesiredRotation are mutually exclusive in practice. The first rotates the character toward its velocity direction (third person), the second smoothly rotates toward where the controller is facing (strafing shooter). Set one, not both. Gravity Direction (UE 5.4+) Custom gravity reorients the entire movement simulation. Walking, falling, and floor detection all respect the gravity direction when HasCustomGravity() returns true . ACharacter API ACharacter provides high level movement actions that delegate to CMC: Jump Properties: bPressedJump , JumpMaxHoldTime , JumpMaxCount , JumpCurrentCount . DoJump(bool bReplayingMoves, float DeltaTime) is the internal method called by CMC to apply the jump velocity. In UE 5.5+ it takes two parameters; the old DoJump(bool)

ue-character-movement