Box2d and opengl update is slow.

rafae11

I have create a simple project and included the box2d library.
could some one please tell me what i am doing wrong.
the falling boxes seem to move very slowly.
advice on how to implement the update function would be appreciated.
thanks.

@
#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QGLWidget>
#include <Box2D/Box2D.h>

const int WIDTH = 640;
const int HEIGHT = 480;
const double FPS = 1.0/30.0;
//const double M_PI = 3.1416;
const float P2M = 20;
const float M2P = 1/P2M;

//! [0]
class GLWidget : public QGLWidget
{
Q_OBJECT

public:
GLWidget(QWidget parent = 0);
~GLWidget();
b2Body addrectangle(int x, int y,int w, int h, bool dyn);
void drawSquare(b2Vec2* points,b2Vec2 center,float angle);
QSize minimumSizeHint() const;
QSize sizeHint() const;

b2World *world;
//! [0]

//! [1]

//! [2]
protected:
void initializeGL();
void paintGL();
void resizeGL(int width, int height);
//! [2]

//! [3]
private:

};
//! [3]

#endif
@
@

#ifndef WINDOW_H
#define WINDOW_H

#include <QWidget>
#include <Box2D/Box2D.h>

QT_BEGIN_NAMESPACE
class QSlider;
QT_END_NAMESPACE
//! [0]
class GLWidget;

class Window : public QWidget
{
Q_OBJECT

public:
Window();

public slots:
void updateworld();
void animateworld();

protected:
void keyPressEvent(QKeyEvent *event);
void mousePressEvent(QMouseEvent *event);

private:
QSlider *createSlider();

GLWidget *glWidget;

};
//! [0]

#endif
@
@

#include <QtWidgets>
#include <QtOpenGL>

#include <math.h>

#include "glwidget.h"

#ifndef GL_MULTISAMPLE
#define GL_MULTISAMPLE 0x809D
#endif

//! [0]
GLWidget::GLWidget(QWidget *parent)
: QGLWidget(QGLFormat(QGL::SampleBuffers), parent)
{

}
//! [0]

//! [1]
GLWidget::~GLWidget()
{
}
//! [1]

//! [2]
QSize GLWidget::minimumSizeHint() const
{
return QSize(WIDTH, HEIGHT);
}
//! [2]

//! [3]
QSize GLWidget::sizeHint() const
//! [3] //! [4]
{
return QSize(WIDTH, HEIGHT);
}
//! [4]

//! [6]
void GLWidget::initializeGL()
{
glMatrixMode(GL_PROJECTION);
glOrtho(0,WIDTH,HEIGHT,0,-1,1);
glMatrixMode(GL_MODELVIEW);
glClearColor(0,0,0,1);

// create world requires gravity
//b2 vector x and y.
world = new b2World(b2Vec2(0.0,9.81));

// provide center point
addrectangle(WIDTH/2,HEIGHT,WIDTH,30,false);

}
//! [6]

//! [7]
void GLWidget::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();

// temporary body
b2Body* tmp = world->GetBodyList();
b2Vec2 points[4];

while(tmp)
{
    for(int i=0;i<4;i++)
    {
        // get current vertex
        points[i]=((b2PolygonShape*)tmp->GetFixtureList()->GetShape())->GetVertex(i);
    }

    drawSquare(points,tmp->GetWorldCenter(),tmp->GetAngle());
    // go through the linked list
    tmp = tmp->GetNext();
    // time to update

}

}
//! [7]

//! [8]
void GLWidget::resizeGL(int width, int height)
{

}
//! [8]

//! [10]
b2Body* GLWidget::addrectangle(int x, int y,int w, int h, bool dyn=true)
{
// need to conver pixels to meter
// create body definition
b2BodyDef bodydef;
bodydef.position.Set(xP2M,yP2M);

if(dyn)
{
    bodydef.type = b2_dynamicBody;
}

//create body after definition
b2Body* body = world->CreateBody(&bodydef);

// create shape
b2PolygonShape shape;
shape.SetAsBox(P2M*(w/2),P2M*(h/2));

// create fixture definition
b2FixtureDef fixturedef;

//pass pointer
fixturedef.shape = &shape;
// defines mass
fixturedef.density = 1.0;

// pass pointer of fixture ref
body->CreateFixture(&fixturedef);

// body create fixture
return body;

}

void GLWidget::drawSquare(b2Vec2* points,b2Vec2 center,float angle)
{
// need to convert back to pixels
glColor3f(1,1,1);
glPushMatrix();
glTranslatef(center.xM2P,center.yM2P,0);
glRotatef(angle180.0/M_PI,0,0,1);
glBegin(GL_QUADS);
for (int i=0; i < 4;i++)
{
glVertex2f(points[i].xM2P,points[i].y*M2P);
}
glEnd();
glPopMatrix();
}
@

@

#include <QApplication>
#include <QDesktopWidget>

#include "window.h"

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
Window window;
window.resize(window.sizeHint());
int desktopArea = QApplication::desktop()->width() *
QApplication::desktop()->height();
int widgetArea = window.width() * window.height();
if (((float)widgetArea / (float)desktopArea) < 0.75f)
window.show();
else
window.showMaximized();
return app.exec();
}
@

@

#include <QtWidgets>
#include <QTimer>

#include "glwidget.h"
#include "window.h"

//! [0]
Window::Window()
{
glWidget = new GLWidget;
QTimer *timer = new QTimer(this);
QTimer *animate = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(updateworld()));
connect(animate, SIGNAL(timeout()),this, SLOT(animateworld()));
animate->start(30);
timer->start(1);
//! [0]

//! [1]
QHBoxLayout *mainLayout = new QHBoxLayout;
mainLayout->addWidget(glWidget);
setLayout(mainLayout);
setWindowTitle(tr("Hello GL"));

}
//! [1]

void Window::keyPressEvent(QKeyEvent *e)
{
if (e->key() == Qt::Key_Escape)
{
close();
}
else if(e->key() ==Qt::Key_A)
{
glWidget->addrectangle(WIDTH/2,HEIGHT/2,20,20,true);
}
else
QWidget::keyPressEvent(e);
}

void Window::mousePressEvent(QMouseEvent *event)
{
int dx = event->x();
int dy = event->y();
glWidget->addrectangle(dx,dy,20,20,true);

}

void Window::updateworld()
{
glWidget->world->Step(FPS,8,3);
}

void Window::animateworld()
{
glWidget->updateGL();
}
@