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Runtime Control

This guide explains how to dynamically control KawaiiPhysics during gameplay.

Dynamic Parameter Changes​

From Blueprint​

Parameters can be changed through Animation Blueprint variables.

// Inside Animation Blueprint
UPROPERTY(BlueprintReadWrite)
float DynamicDamping = 0.1f;

From C++​

// Get AnimInstance and change parameters
UAnimInstance* AnimInstance = Mesh->GetAnimInstance();
// Expose parameters through custom AnimInstance class

Enable/Disable Toggle​

Pause​

UPROPERTY()
bool bEnabled = true;

Use Cases​

  • Disable during cutscenes
  • Disable during pause menu
  • Disable based on LOD

Dynamic External Force Application​

SetExternalForce​

// Explosion impact
void ApplyExplosionForce(FVector ExplosionLocation, float Force)
{
    FVector Direction = (BoneLocation - ExplosionLocation).GetSafeNormal();
    SetExternalForce(Direction * Force);
}

Decay Over Time​

void Tick(float DeltaTime)
{
    // Gradually decay external force
    CurrentExternalForce *= FMath::Exp(-DecayRate * DeltaTime);
    SetExternalForce(CurrentExternalForce);
}

Reset​

Returns physics state to initial state.

// Reset physics state
ResetDynamics();

Use Cases​

  • After teleport
  • During animation transitions
  • On respawn

Event Integration​

AnimNotify Support​

Version Info

Added in v1.17.0

KawaiiPhysics-specific AnimNotifies are provided.

AnimNotify_KawaiiPhysics_ResetDynamics

Resets physics state. Use for teleports or animation transitions.

AnimNotify_KawaiiPhysics_SetExternalForce

Sets external force. Use for wind pressure at jump start, etc.

AnimNotifyState: Set Alpha​

Version Info

Added in v1.20.0

AnimNotifyState that can dynamically change physics blend ratio during animation.

Animation Timeline:
[=======================================]
     [--Set Alpha: 0.0 -> 1.0--]
     ↑                        ↑
     Start (Physics OFF)      End (Physics ON)

Use Cases:

  • Disable physics only during specific animations
  • Smooth blending during animation transitions
  • Control during cutscenes

Custom AnimNotify​

Change physics parameters from Anim Notify:

void UAnimNotify_KPForce::Notify(...)
{
    // Apply external force at jump start
    KawaiiPhysics->SetExternalForce(FVector(0, 0, 100));
}

Gameplay Events​

// When damage is received
void OnDamageReceived(float Damage, FVector HitDirection)
{
    // Reflect impact in physics
    float ImpactForce = Damage * 10.0f;
    KawaiiPhysics->SetExternalForce(HitDirection * ImpactForce);
}

Blueprint Function Library​

It's convenient to make common operations into a library.

UCLASS()
class UKawaiiPhysicsLibrary : public UBlueprintFunctionLibrary
{
    UFUNCTION(BlueprintCallable)
    static void ApplyImpulse(AActor* Actor, FVector Impulse);

    UFUNCTION(BlueprintCallable)
    static void ResetAllKawaiiPhysics(AActor* Actor);
};

For more details, see API Reference.