helloworld-box2d.cpp

#include <iostream>
#include <iomanip>
#include <Box2D/Box2D.h>

using namespace std;

int main()
{
  //Construct a b2World
	b2Vec2 gravity(0.0f, -10.0f);
	b2World world(gravity);

  //Request b2World's body factory to construct a b2Body
	b2BodyDef groundBodyDef;
	groundBodyDef.position.Set(0.0f, -10.0f);
	b2Body* groundBody = world.CreateBody(&groundBodyDef);

  //Request b2Body's fixture factory to construct a fixture (a b2PolygonShape in this case)
	b2PolygonShape groundBox;
	groundBox.SetAsBox(50.0f, 10.0f);
	groundBody->CreateFixture(&groundBox, 0.0f);

  
  //Request b2World's body factory to construct a dynamic b2Body
	b2BodyDef dynamicBodyDef;
	dynamicBodyDef.position.Set(0.0f, 4.0f);
	dynamicBodyDef.type = b2_dynamicBody;
	b2Body* dynamicBody = world.CreateBody(&dynamicBodyDef);

  //Request b2Body's fixture factory to construct a fixture (a b2PolygonShape in this case)
	b2PolygonShape dynamicBox;
	dynamicBox.SetAsBox(1.0f, 1.0f);

	b2FixtureDef fixtureDef;
	fixtureDef.shape = &dynamicBox;
	fixtureDef.density = 1.0f;
	fixtureDef.friction = 0.3f;
	dynamicBody->CreateFixture(&fixtureDef);

	// Prepare for simulation. Typically we use a time step of 1/60 of a
	// second (60Hz) and 10 iterations. This provides a high quality simulation
	// in most game scenarios.
	float32 timeStep = 1.0f / 60.0f;
	int32 velocityIterations = 6;
	int32 positionIterations = 2;

	// This is our little game loop.
	for (int32 i = 0; i < 60; ++i)
	{
		// Instruct the world to perform a single step of simulation.
		// It is generally best to keep the time step and iterations fixed.
		world.Step(timeStep, velocityIterations, positionIterations);

		// Now print the position and angle of the body.
		b2Vec2 position = dynamicBody->GetPosition();
		float32 angle = dynamicBody->GetAngle();

    cout.width(7);
    cout.precision(2);
    cout.setf(ios::fixed);
		cout << position.x << " "
         << position.y << " "
         << angle << endl;
	}

	return 0;
}