hello_world.cpp

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// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#include "box2d/box2d.h"
#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include "doctest.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.
DOCTEST_TEST_CASE("hello world")
{
        // 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.
        float timeStep = 1.0f / 60.0f;
        int32 velocityIterations = 6;
        int32 positionIterations = 2;

        b2Vec2 position = body->GetPosition();
        float angle = body->GetAngle();

        // 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.
                position = body->GetPosition();
                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.

        CHECK(b2Abs(position.x) < 0.01f);
        CHECK(b2Abs(position.y - 1.01f) < 0.01f);
        CHECK(b2Abs(angle) < 0.01f);
}