import direct.directbase.DirectStart
from direct.showbase.DirectObject import DirectObject
from panda3d.core import Vec3
from panda3d.core import Point3
from panda3d.core import TransformState
from panda3d.bullet import BulletWorld
from panda3d.bullet import BulletPlaneShape
from panda3d.bullet import BulletRigidBodyNode
from panda3d.bullet import BulletBoxShape
from panda3d.bullet import BulletDebugNode
from panda3d.bullet import BulletSliderConstraint

base.setBackgroundColor(0.0, 0.0, 0.6, 1)
base.setFrameRateMeter(True)

base.cam.setPos(0, -20, 0)
base.cam.lookAt(0, 0, 0)

# Debug
debugNP = render.attachNewNode(BulletDebugNode('Debug'))
debugNP.show()
debugNP.node().setVerbose(True)

# World
world = BulletWorld()
world.setGravity(Vec3(0, 0, -9.81))
world.setDebugNode(debugNP.node())

# Box 1
shape = BulletBoxShape(Vec3(.5, .5, .5))
node = BulletRigidBodyNode('box1')
node.addShape(shape)
np1 = render.attachNewNode(node)
np1.setPos(0, 0, 4)
world.attachRigidBody(np1.node())

# Box 2
shape = BulletBoxShape(Vec3(.3, .3, .3))
node = BulletRigidBodyNode('box2')
node.setMass(1)
node.addShape(shape)
np2 = render.attachNewNode(node)
np2.setPos(0, 0, 2)
world.attachRigidBody(np2.node())

# Slider
t1 = TransformState.makePosHpr(Point3(0, 0, -1), Vec3(0, 0, 45))
t2 = TransformState.makePosHpr(Point3(0, 0, 0), Vec3(0, 0, 0))
con = BulletSliderConstraint(np1.node(), np2.node(), t1, t2, True)
con.setLowerLinearLimit(1)
con.setUpperLinearLimit(8)
world.attachConstraint(con)

# Update
def update(task):
  dt = globalClock.getDt()
  world.doPhysics(dt)
  return task.cont

taskMgr.add(update, 'update')
run()