bounce.py

from __future__ import absolute_import
from repeat import RepeatTimer
from visual import *

class Bounce:
    aliases = 'bounce'
    description = 'VPython Bounce Test'

    def execute(self, expression, context):
        expression = expression.strip()

        if expression == 'quit':
            context.release()
            visual.scene.visible = False
            self.r.cancel()

            return 'Exit bounce'
        elif context.owner != self:
            context.claim_for(self)
            visual.scene.visible = True

            # scene setup
            floor = box(length=4, height=0.5, width=4, color=color.blue)

            ball = sphere(pos=(0,4,0), color=color.red)
            ball.velocity = vector(0,-1,0)

            def update():
                dt = 0.01

                ball.pos += ball.velocity*dt
                if ball.y < 1:
                    ball.velocity.y *= -1
                else:
                    ball.velocity.y -= 9.8*dt

            self.r = RepeatTimer(0.01, update)
            self.r.run()

repeat.py

# http://g-off.net/software/a-python-repeatable-threadingtimer-class
# Copyright (c) 2009 Geoffrey Foster
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use,
# copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following
# conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.
from threading import Event, Thread

class RepeatTimer(Thread):
    def __init__(self, interval, function, iterations=0, args=[], kwargs={}):
        Thread.__init__(self)
        self.interval = interval
        self.function = function
        self.iterations = iterations
        self.args = args
        self.kwargs = kwargs
        self.finished = Event()

    def run(self):
        count = 0
        while not self.finished.is_set() and (self.iterations <= 0 or count < self.iterations):
            self.finished.wait(self.interval)
            if not self.finished.is_set():
                self.function(*self.args, **self.kwargs)
                count += 1

    def cancel(self):
        self.finished.set()