PyQt + PyBox2D

#/usr/bin/env python

import math
import sys
from Box2D import *
from PyQt4.QtCore import *
from PyQt4.QtGui import *


BODYCOUNT = 100
TIMESTEP = 1.0 / 30.0
FRAME_RATE = 60

DEGTORAD = 2.0 * math.pi / 360.0
RADTODEG = 1.0 / DEGTORAD

DENSITY = 1.0
FRICTION = 0.3
RESTITUTION = 0.3


class QGraphicsBox2DPolygonItem(QGraphicsPolygonItem):
    def __init__(self, world, parent=None):
        super(QGraphicsBox2DPolygonItem, self).__init__(parent)

        self.world = world
        self.body = 0

    def setup(self):
        # Create body with start-up position and rotation
        bodyDef = b2BodyDef()
        bodyDef.position = (self.x(), -self.y())
        bodyDef.angle = -self.rotation() * DEGTORAD
        self.body = self.world.CreateBody(bodyDef)

        # Assign shape to polygon body
        shapeDef = b2PolygonDef()
        shapeDef.density = DENSITY
        shapeDef.friction = FRICTION
        shapeDef.restitution = RESTITUTION

        vertices = [(vertex.x(), -vertex.y()) for vertex in self.polygon()]
        shapeDef.setVertices(vertices)

        self.body.CreateShape(shapeDef)

        # Setup default mass
        self.body.SetMassFromShapes()

    def adjust(self):
        """Update QGraphicsItem's position and rotation from body."""
        (x, y) = self.body.GetPosition()
        angle = self.body.GetAngle()
        self.setPos(x, -y)
        self.setRotation(-angle * RADTODEG)


class Simulator(QObject):
    def __init__(self, scene, parent=None):
        super(Simulator, self).__init__(parent)
        self.timerId = 0
        self.bodyItems = []

        # Define world, gravity, doSleep
        worldAABB = b2AABB()
        worldAABB.lowerBound = (-200, -100)
        worldAABB.upperBound = (200, 500)
        gravity = (0.0, -10.0)
        self.world = b2World(worldAABB, gravity, True)

        # Background item (not part of b2 world)
        backBlock = scene.addRect(-100, -40, 200, 60)
        backBlock.setBrush(QColor(93, 83, 37))
        backBlock.setZValue(-1)
        backBlock.setPen(QPen(Qt.black, 1))

        bodyDef = b2BodyDef()
        shapeDef = b2PolygonDef()

        # Rigid ground item
        groundItem = scene.addRect(-100, -10, 200, 20)
        groundItem.setParentItem(backBlock)
        groundItem.setBrush(QColor(178, 192, 160))
        groundItem.setPos(0, 10)
        groundItem.setPen(QPen(Qt.NoPen))
        bodyDef.position = (0.0, -10)
        shapeDef.SetAsBox(100.0, 10.0)
        groundBody = self.world.CreateBody(bodyDef)
        groundBody.CreateShape(shapeDef)

        # Rigid left and right block items
        for (x, y) in ((-95, -25), (95, -25)):
            blockItem = scene.addRect(-5, -15, 10, 45)
            blockItem.setParentItem(backBlock)
            blockItem.setPen(QPen(Qt.NoPen))
            blockItem.setBrush(QColor(178, 192, 160))
            blockItem.setPos(x, y)
            bodyDef.position = (x, 20.0)
            shapeDef.SetAsBox(5.0, 20.0)
            body = self.world.CreateBody(bodyDef)
            body.CreateShape(shapeDef)

        # Rigid elllipse item * 3
        for (x, y) in ((0, -55), (-30, -50), (30, -50)):
            ellipse = scene.addEllipse(-5, -5, 10, 10)
            ellipse.setPos(x, y)
            ellipse.setPen(QPen(Qt.NoPen))
            ellipse.setBrush(Qt.black)
            bodyDef.position = (x, -y)
            ellipseDef = b2CircleDef()
            ellipseDef.radius = 5
            ellipseBody = self.world.CreateBody(bodyDef)
            ellipseBody.CreateShape(ellipseDef)

        # Create lots of little triangles with random pos, rotation, color
        geometry = QPolygonF()
        for (x, y) in ((0, -10), (-5, 0), (5, 0)):
            geometry << QPointF(x, y)
        for i in range(BODYCOUNT):
            polygon = QGraphicsBox2DPolygonItem(self.world)
            polygon.setPos(-20 + qrand() % 40, -75 - qrand() % 150)
            polygon.setRotation(qrand() % 360)
            polygon.setPolygon(geometry)
            polygon.setBrush(QColor(128 + qrand() % 128,
                                    128 + qrand() % 128,
                                    128 + qrand() % 128))
            polygon.setup()
            scene.addItem(polygon)
            self.bodyItems.append(polygon)

    def start(self):
        if self.timerId == 0:
            self.timerId = self.startTimer(1000.0 / FRAME_RATE)

    def timerEvent(self, event):
        if event.timerId() == self.timerId:
            self.world.Step(TIMESTEP, 10, 8)
            for body in self.bodyItems:
                body.adjust()

        QObject.timerEvent(self, event)


def main():
    app = QApplication(sys.argv)

    qsrand(QTime().secsTo(QTime.currentTime()))

    scene = QGraphicsScene()
    scene.setItemIndexMethod(QGraphicsScene.NoIndex)
    scene.setBackgroundBrush(Qt.white)
    scene.setSceneRect(-110, -150, 220, 175)

    view = QGraphicsView(scene)
    view.setViewportUpdateMode(QGraphicsView.FullViewportUpdate)
    view.setRenderHint(QPainter.Antialiasing)
    view.scale(2, 2)
    view.show()

    simulator = Simulator(scene)
    simulator.start()

    return app.exec_()


if __name__ == '__main__':
    main()