Set's the gravity for a physics shape object.
Setting this changes the default gravity of [0,-9.8,0].
floor = viz.add('tut_ground.wrl')
shape1 = floor.collidePlane()
ball = viz.add('ball.wrl')
shape = ball.collideSphere()
ball.setPosition(0,5,4)
viz.phys.setGravity(0,-2) #Sets the Y plane gravity to -2
vizact.onkeydown(' ', viz.phys.enable)