LegConstraintComponent.cpp

#include "LegConstraintComponent.h"

ULegConstraintComponent::ULegConstraintComponent() {
	PrimaryComponentTick.bCanEverTick = true;
}

void ULegConstraintComponent::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction * ThisTickFunction)
{
	Super::TickComponent(DeltaTime, TickType, ThisTickFunction);
	if (!Pelvis || !LeftLeg || !RightLeg || !LeftKnee || !RightKnee)
		return;

	const FVector LeftKneePos = LeftKnee->GetActorLocation();
	const FVector RightKneePos = RightKnee->GetActorLocation();
	//UE_LOG(LogTemp, Warning, TEXT("%f %f %f"), LeftKneePos.X, LeftKneePos.Y, LeftKneePos.Z);
	const FVector KneeMid = FMath::Lerp(LeftKneePos, RightKneePos, 0.5f);

	const float KneeDist = FVector::Dist(LeftKneePos, RightKneePos);
	//UE_LOG(LogTemp, Warning, TEXT("%f"), KneeDist);

	for (int i = 0; i < Number; ++i) {
		const float Degree = (float(i) / Number) * 360;
		const float Radian = FMath::DegreesToRadians(Degree);
		const FVector RelativePos = { 
			FMath::Sin(Radian) * KneeDist, 
			FMath::Cos(Radian) * KneeDist,
			0.0f
		};

		
		FVector Pos = KneeMid + RelativePos;

		const float LeftDist = FVector::Dist(Pos, LeftKneePos);
		const float RightDist = FVector::Dist(Pos, RightKneePos);
		const float ClosestBlend = LeftDist / RightDist;
		Pos.Z = FMath::Lerp(LeftKneePos.Z, RightKneePos.Z, ClosestBlend);

		const FTransform Transform = FTransform(FQuat::Identity, Pos, FVector(0.5f));

		UpdateInstanceTransform(i, Transform, true);
	}

	MarkRenderStateDirty();
}

void ULegConstraintComponent::BeginPlay()
{
	Super::BeginPlay();
	
	for (int i = 0; i < Number; ++i) {
		AddInstanceWorldSpace(FTransform(FQuat::Identity, FVector(0, 0, 0), FVector(0.5f)));
	}
}

LegConstraintComponent.h

#pragma once

#include "CoreMinimal.h"
#include "Components/InstancedStaticMeshComponent.h"
#include "LegConstraintComponent.generated.h"

/**
 * 
 */
UCLASS(ClassGroup = (Custom), meta = (BlueprintSpawnableComponent))
class TESTBENCH_API ULegConstraintComponent : public UInstancedStaticMeshComponent
{
	GENERATED_BODY()
protected:
	virtual void BeginPlay() override;
public:
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "LegConstraint")
		int Number = 16;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "LegConstraint")
		AActor *Pelvis;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "LegConstraint")
		AActor *LeftLeg;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "LegConstraint")
		AActor *RightLeg;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "LegConstraint")
		AActor *LeftKnee;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "LegConstraint")
		AActor *RightKnee;

	ULegConstraintComponent();
	virtual void TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction) override;
};