CollisionHandlerFloor doesn't work

Scripting Issues
1

Hi,
i tried to make the CollisionHandlerFloor works, but i can’t.
in this program, the panda(self.player) 'z coordinate is supposed to be the same as the smiley actor:

import direct.directbase.DirectStart
from direct.showbase import DirectObject
from pandac.PandaModules import *
from direct.actor import Actor

class World(DirectObject.DirectObject):
    def __init__(self):
        base.ctrav = CollisionTraverser('trverser')
        self._createPlayer()
        
    def _createPlayer(self):
#create the panda:
        self.player = Actor.Actor('panda')
        self.player.reparentTo(render)
        cplayer = self.player.attachNewNode(CollisionNode('player'))
        cplayer.node().addSolid(CollisionRay(0, 0, 0, 0, 0, -1))
        cplayer.show()

# create the smiley(the ground)
        smiley = loader.loadModel('smiley')
        smiley.reparentTo(render)
        self._initSphereShape(smiley)


#Create the collision floor handler
        lifter = CollisionHandlerFloor()
        base.ctrav.addCollider(cplayer, lifter)
        lifter.addCollider(cplayer, self.player)

        smiley.posInterval(2, Point3(0, 0, -10), Point3(0, 0, 0)).loop()

    def _initSphereShape(self, obj):
        bounds = obj.getChild(0).getBounds()
        center = bounds.getCenter()
        radius = bounds.getRadius()
        name = obj.getName()
        cnodePath = obj.attachNewNode(CollisionNode(name))
        cnodePath.node().addSolid(CollisionSphere(center, radius))
        cnodePath.show()
        return cnodePath
    
World()
run()

but the panda doesn’t move:

2

The correct attribute is cTrav.