chain.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# C++ version Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
# Python version by Ken Lauer / sirkne at gmail dot com
#
# This software is provided 'as-is', without any express or implied
# warranty.  In no event will the authors be held liable for any damages
# arising from the use of this software.
# Permission is granted to anyone to use this software for any purpose,
# including commercial applications, and to alter it and redistribute it
# freely, subject to the following restrictions:
# 1. The origin of this software must not be misrepresented; you must not
# claim that you wrote the original software. If you use this software
# in a product, an acknowledgment in the product documentation would be
# appreciated but is not required.
# 2. Altered source versions must be plainly marked as such, and must not be
# misrepresented as being the original software.
# 3. This notice may not be removed or altered from any source distribution.

from .framework import (Framework, main)
from Box2D.b2 import (edgeShape, polygonShape, fixtureDef)

# This test uses the alternative syntax offered by Box2D.b2, so you'll notice
# that all of the classes that normally have 'b2' in front of them no longer
# do. The choice of which to use is mostly stylistic and is left up to the
# user.


class Chain (Framework):
    name = "Chain"

    def __init__(self):
        super(Chain, self).__init__()

        # The ground
        ground = self.world.CreateBody(
            shapes=edgeShape(vertices=[(-40, 0), (40, 0)])
        )

        plank = fixtureDef(
            shape=polygonShape(box=(0.6, 0.125)),
            density=20,
            friction=0.2,
        )

        # Create one Chain (Only the left end is fixed)
        prevBody = ground
        y = 25
        numPlanks = 30
        for i in range(numPlanks):
            body = self.world.CreateDynamicBody(
                position=(0.5 + i, y),
                fixtures=plank,
            )

            # You can try a WeldJoint for a slightly different effect.
            # self.world.CreateWeldJoint(
            self.world.CreateRevoluteJoint(
                bodyA=prevBody,
                bodyB=body,
                anchor=(i, y),
            )

            prevBody = body

if __name__ == "__main__":
    main(Chain)