How do I create a stable physics constraint between bones of different characters?

Development Programming & Scripting
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1

I’ve tried to setup a system to make 2 characters holding hands with a physics simulated constraint (visually similar to what Ico does). As soon as the hands are close enough, I run the following piece of code inside a character

// Enable ragdoll for right arm
    GetMesh()->SetEnableGravity(true);
	GetMesh()->SetCollisionProfileName("Ragdoll");
	
	GetMesh()->IgnoreActorWhenMoving(TheOtherCharacter, true);
	GetMesh()->SetAllBodiesBelowSimulatePhysics(FName("upperarm_r"), true, true);
	GetMesh()->SetAllBodiesBelowPhysicsBlendWeight(FName("upperarm_r"), 1.f);

// Create constraint
	HandConstraint = NewObject<UPhysicsConstraintComponent>(this);
	HandConstraint->RegisterComponent();
	HandConstraint->AttachToComponent(GetMesh(), FAttachmentTransformRules::KeepWorldTransform, FName("hand_r"));
	HandConstraint->SetDisableCollision(true);

	HandConstraint->SetConstrainedComponents(
		GetMesh(), FName("hand_r"),
		TheOtherCharacter->GetMesh(), FName("hand_l")
	);
	HandConstraint->SetDisableCollision(true);
	HandConstraint->ConstraintInstance.EnableProjection();

// Constraint configuration
	HandConstraint->SetLinearXLimit(ELinearConstraintMotion::LCM_Limited, MaxDistance);
	HandConstraint->SetLinearYLimit(ELinearConstraintMotion::LCM_Limited, MaxDistance);
	HandConstraint->SetLinearZLimit(ELinearConstraintMotion::LCM_Limited, MaxDistance);
	
	HandConstraint->ConstraintInstance.ProfileInstance.LinearLimit.bSoftConstraint = true;
	HandConstraint->ConstraintInstance.ProfileInstance.LinearLimit.Stiffness = LinkStiffness;
	HandConstraint->ConstraintInstance.ProfileInstance.LinearLimit.Damping = LinkDamping;
	
	HandConstraint->SetAngularSwing1Limit(EAngularConstraintMotion::ACM_Limited, 45.f);
	HandConstraint->SetAngularSwing2Limit(EAngularConstraintMotion::ACM_Limited, 45.f);
	HandConstraint->SetAngularTwistLimit(EAngularConstraintMotion::ACM_Limited, 20.f);

I tried varying the parameters MaxDistance, LinkStiffness and LinkDamping and I tried making the right hand heavier, but the arm explodes everytime.

stream

What parameters might be causing this? Should I make all bones heavier?

2

I fixed it!

HandConstraint->AttachToComponent(GetMesh(), FAttachmentTransformRules::SnapToTargetNotIncludingScale, FName("hand_r"));

Snapping the HandConstraint directly to the right location works! Now I have to balance the parameters to make it a bit more stable but the connection is fine. I also have created the reciprocal constraint on the left hand of the companion character to make it more natural