HelloWorld.cpp

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/*
* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
*
* 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.
*/

#include <Box2D/Box2D.h>

#include <stdio.h>

// This is a simple example of building and running a simulation
// using Box2D. Here we create a large ground box and a small dynamic
// box.
// There are no graphics for this example. Box2D is meant to be used
// with your rendering engine in your game engine.
int main(int argc, char** argv)
{
        B2_NOT_USED(argc);
        B2_NOT_USED(argv);

        // Define the gravity vector.
        b2Vec2 gravity(0.0f, -10.0f);

        // Construct a world object, which will hold and simulate the rigid bodies.
        b2World world(gravity);

        // Define the ground body.
        b2BodyDef groundBodyDef;
        groundBodyDef.position.Set(0.0f, -10.0f);

        // Call the body factory which allocates memory for the ground body
        // from a pool and creates the ground box shape (also from a pool).
        // The body is also added to the world.
        b2Body* groundBody = world.CreateBody(&groundBodyDef);

        // Define the ground box shape.
        b2PolygonShape groundBox;

        // The extents are the half-widths of the box.
        groundBox.SetAsBox(50.0f, 10.0f);

        // Add the ground fixture to the ground body.
        groundBody->CreateFixture(&groundBox, 0.0f);

        // Define the dynamic body. We set its position and call the body factory.
        b2BodyDef bodyDef;
        bodyDef.type = b2_dynamicBody;
        bodyDef.position.Set(0.0f, 4.0f);
        b2Body* body = world.CreateBody(&bodyDef);

        // Define another box shape for our dynamic body.
        b2PolygonShape dynamicBox;
        dynamicBox.SetAsBox(1.0f, 1.0f);

        // Define the dynamic body fixture.
        b2FixtureDef fixtureDef;
        fixtureDef.shape = &dynamicBox;

        // Set the box density to be non-zero, so it will be dynamic.
        fixtureDef.density = 1.0f;

        // Override the default friction.
        fixtureDef.friction = 0.3f;

        // Add the shape to the body.
        body->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 = body->GetPosition();
                float32 angle = body->GetAngle();

                printf("%4.2f %4.2f %4.2f\n", position.x, position.y, angle);
        }

        // When the world destructor is called, all bodies and joints are freed. This can
        // create orphaned pointers, so be careful about your world management.

        return 0;
}