MotionAttributeSet

MotionAttributeSet is the default GAS AttributeSet for Motion movement and stamina attributes. It can synchronize selected attributes with CharacterMovementComponent.

Requirements

• An AbilitySystemComponent that can own AttributeSets
• Gameplay Ability System initialized
• Character with standard UCharacterMovementComponent

No additional GameplayEffects are required just to define the attributes.

Setup Reference

UMotionAttributeSet can be added to any ASC used by your character setup. Motion can also discover compatible attributes by name on a project-specific AttributeSet.

Default values are set on initialization. To override default values, use a DataTable with row type AttributeMetaData.

Behavior

When attributes change, the AttributeSet clamps values, updates CharacterMovementComponent where appropriate, fires change delegates, and replicates attributes through OnRep functions in multiplayer.

WalkSpeed syncs to both MaxWalkSpeed and MaxWalkSpeedCrouched. The crouched speed is updated proportionally so its ratio to walk speed is preserved.

When MotionWalkComponent is present, the assigned walk profile's BaseWalkSpeed is the initial source of truth for walking speed. The Walk Component applies that value to CharacterMovementComponent->MaxWalkSpeed, writes it to the authoritative WalkSpeed base value when the ASC is available, and syncs CMC from the current effective WalkSpeed. Configure base walking speed on the walk profile instead of editing the CMC walk speed independently.

JumpVelocity syncs to JumpZVelocity.

Expandability

• PostAttributeChange(): implemented by Motion to sync selected attributes to CMC.
• PreAttributeChange(): inherited extension point for validation before changes.
• PostGameplayEffectExecute(): inherited extension point for reacting to GameplayEffect execution.
• GetLifetimeReplicatedProps(): implemented by Motion so all Motion attributes replicate.

Gameplay Attributes

WalkSpeed

• Type: FGameplayAttributeData
• Default: 600.0
• Replication: OnRep_WalkSpeed
• Clamping: minimum 0.0
• Auto-sync: CharacterMovementComponent->MaxWalkSpeed
• Description: base walking speed for character movement. With MotionWalkComponent, the base value starts from the assigned walk profile's BaseWalkSpeed.

SprintSpeed

• Type: FGameplayAttributeData
• Default: 300.0
• Replication: OnRep_SprintSpeed
• Clamping: minimum 0.0
• Auto-sync: none
• Description: additive sprint speed modifier.

JumpVelocity

• Type: FGameplayAttributeData
• Default: 420.0
• Replication: OnRep_JumpVelocity
• Clamping: minimum 0.1
• Auto-sync: CharacterMovementComponent->JumpZVelocity
• Description: jump velocity for character jump mechanics.

Stamina

• Type: FGameplayAttributeData
• Default: 5.0
• Replication: OnRep_Stamina
• Clamping: 0.0 to MaxStamina
• Description: current stamina amount for sprint mechanics.

MaxStamina

• Type: FGameplayAttributeData
• Default: 5.0
• Replication: OnRep_MaxStamina
• Clamping: none
• Description: maximum stamina capacity.

StaminaRegenRate

• Type: FGameplayAttributeData
• Default: 1.0
• Replication: OnRep_StaminaRegenRate
• Clamping: none
• Description: stamina regenerated per second when not sprinting.

StaminaDrainRate

• Type: FGameplayAttributeData
• Default: 1.0
• Replication: OnRep_StaminaDrainRate
• Clamping: none
• Description: stamina consumed per second when sprinting.

Accessors

Each attribute gets accessor functions through the ATTRIBUTE_ACCESSORS macro.

For WalkSpeed, the generated functions are:

static FGameplayAttribute GetWalkSpeedAttribute();
float GetWalkSpeed() const;
void SetWalkSpeed(float NewValue);
void InitWalkSpeed(float InitialValue);

C++ Access

The generated accessors are native C++ helpers on the AttributeSet:

float CurrentSpeed = AttributeSet->GetWalkSpeed();

AttributeSet->SetWalkSpeed(800.0f);
AttributeSet->SetStamina(3.0f);

AttributeSet->InitWalkSpeed(600.0f);
AttributeSet->InitMaxStamina(10.0f);

FGameplayAttribute WalkSpeedAttr = UMotionAttributeSet::GetWalkSpeedAttribute();
FGameplayAttribute StaminaAttr = UMotionAttributeSet::GetStaminaAttribute();

Blueprint Access

Get Walk Speed from Attribute Set
- Target: Motion Attribute Set
- Return: Float

Set Walk Speed on Attribute Set
- Target: Motion Attribute Set
- New Value: 800.0

Gameplay Effect Access

Gameplay Effect: GE_Motion_SprintSpeed
- Attribute: MotionAttributeSet.WalkSpeed
- Modifier Op: Add
- Magnitude: 300.0
- Duration: Infinite

Blueprint Helper Functions

GetStaminaPercent()

Returns current stamina as a normalized 0.0 to 1.0 value. Use it for UI stamina bars.

HasEnoughStamina(float Required)

Returns true when current stamina is greater than or equal to the required amount. Use it for ability cost checks.

Stamina System Integration

When MotionSprintingComponent uses stamina:

1. Stamina drains while sprinting.
2. Stamina regenerates when not sprinting.
3. Stamina clamps between 0 and MaxStamina.
4. Exhaustion triggers at 0.

Replication

All attributes replicate with OnRep functions:

• OnRep_WalkSpeed(): syncs walk speed on clients.
• OnRep_SprintSpeed(): updates sprint speed.
• OnRep_JumpVelocity(): syncs jump velocity.
• OnRep_Stamina(): updates stamina display.
• OnRep_MaxStamina(): updates stamina maximum.
• OnRep_StaminaRegenRate(): updates regeneration rate.
• OnRep_StaminaDrainRate(): updates drain rate.

Common Gameplay Effects

• Sprint speed increase: add +300 to WalkSpeed, usually from SprintSpeed.
• Crouch speed decrease: add -200 to WalkSpeed.
• Jump boost: multiply JumpVelocity, for example by 1.5.
• Stamina drain: add a negative stamina magnitude per second.

Performance Notes

• Attribute changes are optimized for frequent updates.
• CMC synchronization happens only when values change.
• Replication uses critical replicated attributes.
• Clamping prevents invalid states automatically.

Client Prediction Handling

When Motion components apply predicted speed changes on clients:

1. The component sets bIsLocallyPredicting with the predicted speed.
2. PostAttributeChange checks whether the client is predicting.
3. If the server value matches within 1.0, prediction is confirmed and cleared.
4. If values differ, the server correction is logged and applied.

The server value is always applied as the authoritative result.