Character

[cyberpunkpor]

Hi

i am trying to make my character rotate, run and walk using bullet.

I know that the a character controller is to be released, but i would appreciate you if you can help me translate this ODE implementation to bullet:

http://www.ogre3d.org/wiki/index.php/Og ... _Character

Or
if you have any demo/paper/article you can share it with me. I just want a simple way to walk, run and rotate.

My game is pretty well integrated, using a physics manager that updates the nodes (Irrlicht) position etc. My main problem, is the physics part of the player (rotation, velocity etc.). You can see the demo on the ball here:

http://video.google.com/videoplay?docid ... 3396&hl=en


Any help will be very appreciated.

Thanks

[Erwin Coumans]

Hi

i am trying to make my character rotate, run and walk using bullet.

I know that the a character controller is to be released, but i would appreciate you if you can help me translate this ODE implementation to bullet:

http://www.ogre3d.org/wiki/index.php/Og ... _Character

It seems to use a dynamic rigid body using a capsule standing on a sphere. You could also use a capsule standing on a raycast.
You can use the Bullet btHingeConstraint, and set the angularOnly mode to true:

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hinge->setAngularOnly(true).

Such hinge also helps keeping a character facing upwards when using a rigid body with just a capsule shape.
As a start, you could try to set linear velocity on the character. Still, it will be tricky to gain full control of the motion.

That is why many approaches don't use dynamic rigid bodies to simulate characters, but kinematic objects. This means you don't take mass and forces into account at all, so that you keep full control.

For the time being, could you try just using a capsule rigid body in combination with an 'angular only' hinge? Another option is to cancel angular effects during rigid body interactions (sliding against walls etc), by using

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rigidbody->setAngularFactor(0.0);

You can combine this with the angular-only hinge.

Hope this helps,
Erwin

[cyberpunkpor]

Thanks for helping out.

It seems to use a dynamic rigid body using a capsule standing on a sphere. You could also use a capsule standing on a raycast.

I am a newbie, so I am starting with a capsule:

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              Physics::Instance().GetBulletTransform(Transform, TObject.Position, TObject.Rotation);
		MotionState = new btDefaultMotionState(Transform);

		Shape = new btCapsuleShape(TObject.Radius,1.8f-2.0f*TObject.Radius);

		// Calculate inertia
		btVector3 LocalInertia;
		Shape->calculateLocalInertia(TObject.Mass, LocalInertia);

		RigidBody = new btRigidBody(TObject.Mass, MotionState, Shape, LocalInertia);
		RigidBody->setUserPointer((void *)this);
		RigidBody->setAngularFactor(0.0f);

		Physics::Instance().GetWorld()->addRigidBody(RigidBody, TObject.CollisionGroup, TObject.CollisionMask);
		RigidBody->setActivationState(DISABLE_DEACTIVATION);

Then i have an event that hooks for keyboard events and i just apply:

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		btVector3 EulerRotation;
		btQuaternion RigidRotation = RigidBody->getOrientation();
		Physics::Instance().QuaternionToEuler(RigidRotation, EulerRotation);

		RigidBody->setAngularVelocity(EulerRotation * btVector3(10*cos(1.0f),0,10*sin(1.0f)));

Then the loop will call a method that updates the node position:

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	// Position
	btPoint3 Point = RigidBody->getCenterOfMassPosition();
	Node->setPosition(vector3df((f32)Point[0], (f32)Point[1], (f32)Point[2]));
	
	// Rotation
	btVector3 EulerRotation;
	btQuaternion RigidRotation = RigidBody->getOrientation();
	Physics::Instance().QuaternionToEuler(RigidRotation, EulerRotation);
	Node->setRotation(vector3df(EulerRotation[0], EulerRotation[1], EulerRotation[2]));

	// Note changes
	if(!MovementChanged && (PreviousPosition != Node->getPosition() || PreviousRotation != Node->getRotation()))
		MovementChanged = true;

	PreviousPosition = Node->getPosition();
	PreviousRotation = Node->getRotation();
	Node->updateAbsolutePosition();

Why the player is not moving or rotating? any clues?

Note that my ball (sphere) is just other object, that inherits from the same class as the class representing my player, so the problem must be the physics / math...

thanks

[Erwin Coumans]

If you choose to use a dynamic rigid body (with positive mass), you better control the character by setting the velocity, and not the position.

Also, make sure to disable deactivation (sleeping):

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rigidbodyCharacter->setActivationState(DISABLE_DEACTIVATION);

Hope this helps,
Erwin

[cyberpunkpor]

Thanks for replying.

SetLinearVelocity can actually move the capsule, but how do I rotate by the X axis, for example and at the same time applying the velocity?

[shogun]

It seems to use a dynamic rigid body using a capsule standing on a sphere. You could also use a capsule standing on a raycast.

I really wonder how this would be done ... I didn't find anything useful in the API and the demos, probably because they are pretty confusing for a newbie. ;)

[Erwin Coumans]

Please check Bullet 2.67 Demos/CharacterDemo. That uses a dynamic rigidbody character.

For next Bullet versions we plan on adding a pure kinematic (non-dynamic) character controller, based on the btCollisionWorld::convexSweepTest.

Thanks,
Erwin

[shogun]

Hello,

thanks for the advice. I looked at the code (and experimented with some values), but I'm still not sure how to let the capsule stand on a raycast. Perhaps some comments in the code would help ...

Regards,
shogun

[mp3butcher]

Hello,
I'm working on behavioral autonomous character controllers for crowd simulating during building escape, and I only use bullet for his accurate collision response whereas my octree first approach ( number of steps integration and force limits drove me mad ).
I test tour character controller and It is exactly what I have to do with my physics/behavioral control/AI modelisation stack.
The only thing i have saw is that character have air control movement that is not very physically natural feature.
A feature that would be great for my use (and certainly other's) is a character/character collision response in order to simulate crowd behaviors. How can I cheat on this deformable object collision response in bullet ( i think of an individual character property as smoothingcollision coeff that pounder the force response between characters )?
Can it be done by a usercollision algorithm ? and if it can be done is there a mean to generalize it for all other shape in the scene?
PS: I would like to introduce a physiological model of character force endurance to check when a human cant handle pression of other..if you've an idea how to extend the character controller i would be glad?

[DDd]

Can i feed motion capture/keyframed data to the static character controller?

What i am thinking is that it may be possible to use the character controller to switch between motion data and ragdoll mode using a blend mode... basically the motion data defines the armature for the animation and the animation is interlaced with dynamic data in regular intervals. Do you think this could be a possibility?