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Panda3D Manual: Types of forces

Panda3D provides two types of forces that you can apply to an object.


LinearVectorForce

A LinearVectorForce treats the object as a point mass. It applies an acceleration in Newtons to the center of mass of the object it was added to. The direction of this force is relative to the orientation of the ForceNode that the LinearVectorForce was applied to.

Note: Since LinearVectorForce treats the object as a point mass, it is not possible to apply a rotation of any kind to your object. For rotational forces, see AngularVectorForce below.

Example:

lvf=LinearVectorForce(1,0,0)  # Push 1 newton in the positive-x direction 
forceNode.addForce(lvf) # Determine coordinate space of this force node
actorNode.getPhysical(0).addLinearForce(lvf) # Add the force to the object


AngularVectorForce

The AngularVectorForce applies a torque to the object it is attached to. The acceleration is in Newtons, and AngularVectorForce may be treated in much the same way as LinearVectorForce. There are, however, some minor differences that that should be taken into account.

AngularVectorForce does not have a .setDependantMass() . The reason for this is simple: mass must be used in the torque calculations. As such, you will want to make sure your forces are sufficiently small or your masses are sufficiently large to keep your rotational velocity sane.

Example:

avf=AngularVectorForce(1,0,0) # Spin around the positive-x axis 
forceNode.addForce(avf) # Determine which positive-x axis we use for calculation
actorNode.getPhysical(0).addAngularForce(avf) # Add the force to the object

One additional caveat with AngularVectorForce: Angular forces will not be processed on your object until an AngularIntegrator is added to the PhysicsManager.

Example:

from panda3d.physics import AngularEulerIntegrator
 
angleInt = AngularEulerIntegrator() # Instantiate an AngleIntegrator()
base.physicsMgr.attachAngularIntegrator(angleInt) # Attatch the AngleIntegrator to the PhysicsManager


Editor's Note: Each type of force should be given it's own page with much more in depth examples, and perhaps a small sample program.