Constrained Character

[LeXXik]

Need some ideas here. I want a character to be influenced by another dynamic body connected to it via a constraint, think a man pulling a rock with a rope up the slope, where a rock would pull the man down if he doesn't put an effort pulling it in opposite direction.

What would be my options to make the character be pulled by the rock down the slope in a controllable fashion? Perhaps by adjusting the strength of the character vs the rigidbody mass it is pulling, or some sort of weighted influence. Would I be able to achieve it with a paired dynamic rigidbody?

Edit: tried using an inner body, but it didn't work, unfortunately - the character is not affected by the constraint, no matter how heavy the linked dynamic object is.

[jrouwe]

There's nothing that would be immediately suitable for this.

1. You could use Character instead of CharacterVirtual, but you would lose stair stepping and slope handling
2. You could perhaps attach your constraint to the inner body (or a seperate kinematic body) and measure the applied impulse on the constraint attached to that body (GetTotalLambda) and apply that manually on your CharacterVirtual

[LeXXik]

measure the applied impulse on the constraint attached to that body (GetTotalLambda)

Hmm, do you mean distanceConstraint.GetTotalLambdaPosition()? That always returns a zero scalar for me.

[jrouwe]

Yes, that's the one for distance constraints. It should return non zero values provided that one of the connected bodies is dynamic and active and obviously something (eg gravity) has to try to pull the constraint apart

[LeXXik]

Hmm. I've modified the constraints example a bit:

// in the beginning
let distanceConstraint;

// distance constraint
for (let z = 0; z < 10; ++z) {
	let body = createBody(creationSettings, z);

	if (prevBody != null) {
		constraintSettings.mPoint1.SetZ(z - 0.5);
		constraintSettings.mPoint2.SetZ(z - 0.5);

		const constraint = constraintSettings.Create(prevBody, body)
		physicsSystem.AddConstraint(constraint);
		if (z === 5) {
			distanceConstraint = Jolt.wrapPointer(constraint, Jolt.DistanceConstraint);
		}
	}
	prevBody = body;
}

// in the end
onExampleUpdate = function (time, deltaTime) {
	if (distanceConstraint) {
		console.log(distanceConstraint.GetTotalLambdaPosition())
	}
}

And I get 0 in the console. Am I missing something?

[jrouwe]

It looks like this should work. I guess I have to do some debugging.

[jrouwe]

I see the mistake now:

distanceConstraint = Jolt.wrapPointer(constraint, Jolt.DistanceConstraint);

should be:

distanceConstraint = Jolt.castObject(constraint, Jolt.DistanceConstraint);

constraint is an object and not a raw address, so you can't use wrapPointer to cast it.

[LeXXik]

Sorry, I keep confusing those 2 methods. Thanks!