Анимация в Box2D

#include "mainwidget.h"
#include "ui_mainwidget.h"
#inclide <QGraphicsSceneMouseEvent>
#include <QDebug>
 
//Box2D units -> scene units
qreal fromB2(qreal value){
    return value*SCALE;
}
 
//scene units -> Box2D units
qreal toB2 (qreal value) {
    return value/SCALE;
}
 
MainWidget::MainWidget (QWidget *parent) :
    QWidget (parent),
    ui (new Ui::MainWidget)
{
    ui -> setupUi(this);
 
    world = new b2World(b2Vec2(0.00f, 10.00f));
    scene = new Scene (0, 0, 8, 6, world);
    ui -> graphicsView -> setScene (scene);
 
    scene -> addRect (scene -> sceneRect());
    scene->addRect(new GroundRect(world, QSize(4, 0.1), QPointF(2, 1), 15));
    scene->addRect(new GroundRect(world, QSize(4, 0.1), QPointF(6, 2), -10));
    scene->addRect(new GroundRect(world, QSize(4, 0.1), QPointF(2, 3), 15));
    scene->addRect(new GroundRect(world, QSize(4, 0.1), QPointF(6, 4), -10));
    scene->addRect(new GroundRect(world, QSize(8, 0.1), QPointF(4, 5.95), 0));
    scene->addRect(new GroundRect(world, QSize(0.1, 1), QPointF(0.05, 5.5), 0));
 
    frameTimer = new QTimer (this);
    connect(frameTimer, SIGNAL(timeout()),
            scene,, SLOT(advance()));
    frameTimer->start(1000/60);
}
 
MainWidget::~MainWidget()
{
    delete ui;
    delete scene;
    delete world;
}
 
Circle::Circle(b2World *world, qreal radius, QPointF initPos) :
    QGraphicsEllipseItem(0)
{
    setRect(-fromB2(radius), -fromB2(radius), fromB2(radius*2), fromB2(radius*2));
    setBrush(QBrush(Qt::green));
    setPos(fromB2(initPos.x()), fromB2(initPos.y()));
 
    b2BodyDef bodyDef;
    bodyDef.type = b2_dynamicBody;
    bodyDef.position.Set(initPos.x(), initPos.y());
    bodyDef.linearDamping = 0.2;
 
    body = world->CreatBody(&bodyDef);
 
    b2CircleShape shape;
    shape.m_radius = radius;
 
    b2Fixture* fixture = body->CreateFixture(&shape, 1.0f);
    fixture->SetRestitution(0.7);
}
 
Circle::~Circle()
{
    body->GetWorld()->DestroyBody(body);
}
 
 
void Circle::advance(int phase)
{
    if (phase) {
        setPos(fromB2(body->GetPosition().x),
               fromB2(body->GetPosition().y));
    }
}
 
GroundRect::GroundRect(b2World *world, QSizeF size, QPointF initPos, qreal angle):
    QGraphicsRestItem(0)
{
    setRect(-fromB2(size.width()/2), -fromB2(size.height()/2),
            fromB2(size.width()), fromB2(size.height()));
    setBrush(QBrush(Qt::gray));
    setPos(fromB2(initPos.x()), fromB2(initPos.y()));
    setRotation(angle);
 
    b2BodyDef bodyDef;
    bodyDef.type = b2_staticBody;
    bodyDef.position.Set(initPos.x(), initPos.y());
    bodyDef.angle = 3.14*angle/180;
 
    body = world->CreatBody(&bodyDef);
 
    b2PolygonShape shape;
    shape.SetAsBox(size.width()/2, size.height()/2);
 
    body->CreateFixture(&shape, 0.0f);
}
 
GroundRect::~GroundRect()
{
    body->GetWorld()->DestroyBody(body);
}
 
Scene::Scene(qreal x, qreal y, qreal width, qreal height, b2World *world)
    : QGraphicsScene(fromB2(x), fromB2(y), fromB2(width), fromB2(height))
{
    this->world = world;
}
 
void Scene::advance()
{
    world->Step(1.00f/60.00, 6, 2);
    QGraphicsScene::advance();
}
 
 
void Scene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    addItem(new Circle(world, o.2,
                       QPointF(toB2 (event->scenePos().x()),
                               toB2 (event->scenePos().y()))));
}