[Pyode-user] Why don't my joints work? (PyODE with PyOgre)

[Andrew D. <ad...@gm...>]

Hi everyone,

I'm experimenting with PyODE and PyOgre at the moment, and have been
working through PyODE's Tutorial 2 (two bodies connected with ball
joints to form a compound pendulum).

I've tried to rewrite Tutorial 2 using PyOgre instead of PyGame. I'd
managed to get an ogre head to fall under gravity without trouble, but
attempting to attach the head to a joint (with the other end fixed),
the joint seems to be completely ignored, with the head merely falling
and not swinging as it ought.

I can't see at all what I'm doing wrong here -- can anyone help me?

Here's the code:


import pyogre.ogre as ogre
import SampleFramework as sf
import ode

class TutorialApplication(sf.Application):
    def __init__(self):
        sf.Application.__init__(self)

        # Set up the physics world
        self.world =3D ode.World()
        self.world.setGravity((0, -9.81, 0))
        self.bodyList =3D []


    def _createScene(self):
        sm =3D self.sceneManager

        # Set up the lighting conditions
        sm.ambientLight =3D (0.7, 0.7, 0.7)


        # Create a disembodied ogre head
        e =3D sm.createEntity("OgreHead", "ogrehead.mesh")
        n =3D sm.rootSceneNode.createChildSceneNode()
        n.attachObject(e)
        pos =3D (100, 200, 0)
        n.position =3D ogre.Vector3(*pos)

        body1 =3D ode.Body(self.world)
        M =3D ode.Mass()
        M.setSphere(2500, 0.05)
        body1.setMass(M)
        body1.setPosition((100, 200, 0))

        # Add it to the body list
        self.bodyList.append((body1, n))

        # Connect body1 with the static environment
        j1 =3D ode.BallJoint(self.world)
        j1.attach(body1, None)
        j1.setAnchor((0, 200, 0))


    def _createFrameListener(self):
        """Creates the FrameListener."""
        self.frameListener =3D PhysicsFrameListener(self.renderWindow,
self.camera, self.world, self.bodyList)
        self.frameListener.showDebugOverlay(True)
        self.root.addFrameListener(self.frameListener)


class PhysicsFrameListener(sf.FrameListener):
    def __init__(self, renderWindow, camera, world, bodyList):
        sf.FrameListener.__init__(self, renderWindow, camera)

        self.world =3D world
        self.bodyList =3D bodyList
        self.time =3D 0.0
        self.dt =3D 0.08


    def frameStarted(self, frameEvent):
        # Step the physics
        self.world.step(self.dt)
        self.time +=3D self.dt

        if False:
            body =3D self.bodyList[0][0]
            x,y,z =3D body.getPosition()
            u,v,w =3D body.getLinearVel()
            print "%1.2fsec: pos=3D(%6.3f, %6.3f, %6.3f)  vel=3D(%6.3f,
%6.3f, %6.3f)" % \
                (self.time, x, y, z, u,v,w)


        # Update the positions of objects
        for body, node in self.bodyList:
            pos =3D body.getPosition()
            node.position =3D ogre.Vector3(*pos)

        return sf.FrameListener.frameStarted(self, frameEvent)



if __name__ =3D=3D "__main__":
    app =3D TutorialApplication()
    app.go()