C++ Pull Constraint

Development World Creation
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1

Hello!

I’m tinkering with constraints and I’d like to drag a ball around by a 1-link-chain.

I’m think that the way to do this is to create a constraint between my ball actor and a handle actor. I would then transform the handle actor around, and it would pull the ball around via the constraint.

I currently am getting no visible interaction between my handle and ball.

I’m using Rama’s tutorial on constraints (https://wiki.unrealengine.com/Physics_Constraints,_Create_New_Constraints_Dynamically_During_Runtime).

Here’s what I have so far to create the constraint:

//set up the constraint instance with all the desired values
	//
	FConstraintInstance ci;
	SetLinearLimits(ci, false, 0, 0, 0, 0);
	SetAngularLimits(ci, 0, 0, 0, 90, 90, 90);

	//New Object
	m_constraint_component = NewObject<UPhysicsConstraintComponent>(Mesh);
	if (!m_constraint_component)
	{
		//UE_LOG constraint UObject could not be created!
		return;
	}

	//~~~~~~~~~~~~~~~~~~~~~~~~
	//Set Constraint Instance!
	m_constraint_component->ConstraintInstance = ci;
	//~~~~~~~~~~~~~~~~~~~~~~~~

	//Attach to Root!
		m_constraint_component->AttachTo(Mesh, NAME_None, EAttachLocation::SnapToTarget);

	//~~~ Init Constraint ~~~
		m_constraint_component->SetConstrainedComponents(Mesh, NAME_None, m_constraint_target, NAME_None);

And here is how I’m moving the handle around:

	//Set World Location
	m_constraint_target->SetWorldLocation(location);

Any ideas/links?

2

I read this post (https://answers.unrealengine.com/questions/25182/physics-constrain-to-axis-in-c.html).

I believe it’s saying in the method SetConstrainedComponents(), my handle should come first, then my ball:

//~~~ Init Constraint ~~~
         m_constraint_component->SetConstrainedComponents(m_constraint_target, NAME_None,Mesh, NAME_None);

This still doesn’t show me any interaction.

However! If I don’t initialize my FConstraintInstance, the ball flops around lol. If I wanted no limits/locks on my constraint, how should I initialize it? 0’s don’t seem to do the trick.

3

Thats because you set everything to free. So it is basically no constraint. Set the zeros to 2. Better read ramas article again