JUCE/examples/Assets/Box2DTests/CollisionProcessing.h

/*
* Copyright (c) 2006-2009 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.
*/

#ifndef COLLISION_PROCESSING_H
#define COLLISION_PROCESSING_H

#include <algorithm>

// This test shows collision processing and tests
// deferred body destruction.
class CollisionProcessing : public Test
{
public:
    CollisionProcessing()
    {
        // Ground body
        {
            b2EdgeShape shape;
            shape.Set(b2Vec2(-50.0f, 0.0f), b2Vec2(50.0f, 0.0f));

            b2FixtureDef sd;
            sd.shape = &shape;;

            b2BodyDef bd;
            b2Body* ground = m_world->CreateBody(&bd);
            ground->CreateFixture(&sd);
        }

        float32 xLo = -5.0f, xHi = 5.0f;
        float32 yLo = 2.0f, yHi = 35.0f;

        // Small triangle
        b2Vec2 vertices[3];
        vertices[0].Set(-1.0f, 0.0f);
        vertices[1].Set(1.0f, 0.0f);
        vertices[2].Set(0.0f, 2.0f);

        b2PolygonShape polygon;
        polygon.Set(vertices, 3);

        b2FixtureDef triangleShapeDef;
        triangleShapeDef.shape = &polygon;
        triangleShapeDef.density = 1.0f;

        b2BodyDef triangleBodyDef;
        triangleBodyDef.type = b2_dynamicBody;
        triangleBodyDef.position.Set(RandomFloat(xLo, xHi), RandomFloat(yLo, yHi));

        b2Body* body1 = m_world->CreateBody(&triangleBodyDef);
        body1->CreateFixture(&triangleShapeDef);

        // Large triangle (recycle definitions)
        vertices[0] *= 2.0f;
        vertices[1] *= 2.0f;
        vertices[2] *= 2.0f;
        polygon.Set(vertices, 3);

        triangleBodyDef.position.Set(RandomFloat(xLo, xHi), RandomFloat(yLo, yHi));

        b2Body* body2 = m_world->CreateBody(&triangleBodyDef);
        body2->CreateFixture(&triangleShapeDef);

        // Small box
        polygon.SetAsBox(1.0f, 0.5f);

        b2FixtureDef boxShapeDef;
        boxShapeDef.shape = &polygon;
        boxShapeDef.density = 1.0f;

        b2BodyDef boxBodyDef;
        boxBodyDef.type = b2_dynamicBody;
        boxBodyDef.position.Set(RandomFloat(xLo, xHi), RandomFloat(yLo, yHi));

        b2Body* body3 = m_world->CreateBody(&boxBodyDef);
        body3->CreateFixture(&boxShapeDef);

        // Large box (recycle definitions)
        polygon.SetAsBox(2.0f, 1.0f);
        boxBodyDef.position.Set(RandomFloat(xLo, xHi), RandomFloat(yLo, yHi));

        b2Body* body4 = m_world->CreateBody(&boxBodyDef);
        body4->CreateFixture(&boxShapeDef);

        // Small circle
        b2CircleShape circle;
        circle.m_radius = 1.0f;

        b2FixtureDef circleShapeDef;
        circleShapeDef.shape = &circle;
        circleShapeDef.density = 1.0f;

        b2BodyDef circleBodyDef;
        circleBodyDef.type = b2_dynamicBody;
        circleBodyDef.position.Set(RandomFloat(xLo, xHi), RandomFloat(yLo, yHi));

        b2Body* body5 = m_world->CreateBody(&circleBodyDef);
        body5->CreateFixture(&circleShapeDef);

        // Large circle
        circle.m_radius *= 2.0f;
        circleBodyDef.position.Set(RandomFloat(xLo, xHi), RandomFloat(yLo, yHi));

        b2Body* body6 = m_world->CreateBody(&circleBodyDef);
        body6->CreateFixture(&circleShapeDef);
    }

    void Step(Settings* settings)
    {
        Test::Step(settings);

        // We are going to destroy some bodies according to contact
        // points. We must buffer the bodies that should be destroyed
        // because they may belong to multiple contact points.
        const int32 k_maxNuke = 6;
        b2Body* nuke[k_maxNuke];
        int32 nukeCount = 0;

        // Traverse the contact results. Destroy bodies that
        // are touching heavier bodies.
        for (int32 i = 0; i < m_pointCount; ++i)
        {
            ContactPoint* point = m_points + i;

            b2Body* body1 = point->fixtureA->GetBody();
            b2Body* body2 = point->fixtureB->GetBody();
            float32 mass1 = body1->GetMass();
            float32 mass2 = body2->GetMass();

            if (mass1 > 0.0f && mass2 > 0.0f)
            {
                if (mass2 > mass1)
                {
                    nuke[nukeCount++] = body1;
                }
                else
                {
                    nuke[nukeCount++] = body2;
                }

                if (nukeCount == k_maxNuke)
                {
                    break;
                }
            }
        }

        // Sort the nuke array to group duplicates.
        std::sort(nuke, nuke + nukeCount);

        // Destroy the bodies, skipping duplicates.
        int32 i = 0;
        while (i < nukeCount)
        {
            b2Body* b = nuke[i++];
            while (i < nukeCount && nuke[i] == b)
            {
                ++i;
            }

            if (b != m_bomb)
            {
                m_world->DestroyBody(b);
            }
        }
    }

    static Test* Create()
    {
        return new CollisionProcessing;
    }
};

#endif