Bullet in 2D?

[Jesse_yay]

Hello everybody.
I'm planning on making a two dimensional game and want to use realistic physics.
Bullet seems like a very good physics engine, is there any way to implement in 2D?

thanks

[Erwin Coumans]

Hello everybody.
I'm planning on making a two dimensional game and want to use realistic physics.
Bullet seems like a very good physics engine, is there any way to implement in 2D?

thanks

You could add a 'planar' constraint that keeps the rigid bodies in a 2D plane. This can be done using the btGeneric6DofConstraint with the correct settings (a sample showing how to do this would be useful indeed).

Alternative, you could check out a very similar physics engine called Box2D. Most of the ideas and algorithms are the same, but then all in 2D.

Hope this helps,
Erwin

[chunky]

I just did this the other day. I was hoping someone here might be able to comment on the validity of what I've done. I created a body with no shape or mass, and just left it. Then create another body [the one I actually wish to attach to the plane z=0] and attach it to the first one with a generic6dof:

Code: Select all

btCollisionShape *mZeroFloorShape;
btRigidBody *mZeroFloorBody;

mZeroFloorShape = NULL;
mZeroFloorBody = new btRigidBody(0,NULL,mZeroFloorShape); // z=0 body
mWorld->addRigidBody(mZeroFloorBody);

is in my main physics class. Then when I create the actual ship bodies, I do thus:

Code: Select all

btRigidBody *mShipBody;

/* Do all the ship-body-creation-stuff */

btGeneric6DofConstraint *mShiptoworld;


btTransform identity = btTransform::getIdentity();
	
mShiptoworld = new btGeneric6DofConstraint(*mShipBody, *mTWPhysics->getZeroPlane(),
							identity, identity, false);

mShiptoworld->setLimit(0,1,0); // Disable X axis limits
mShiptoworld->setLimit(1,1,0); // Disable Y axis limits
mShiptoworld->setLimit(2,0,0); // Set the Z axis to always be equal to zero

mShiptoworld->setLimit(3,1,0); // Uncap the rotational axes
mShiptoworld->setLimit(4,1,0); // Uncap the rotational axes
mShiptoworld->setLimit(5,1,0); // Uncap the rotational axes
	
mTWPhysics->addConstraintToWorld(mShiptoworld);// small wrapper 

Does that look right, to the more experienced bullet coders here?

Thank-you very much,
Gary (-;

[Cleanrock]

do this work for you ?

btw, when i searched this forum to find this topic using "bullet in 2d" as search phrase it failed saying that words are too common or too short, hopefully this can be improved

[chunky]

Well, it certainly *seems* to be working...

Gary (-;