axmol/tests/cpp-tests/Source/Box2DTestBed/tests/collision_processing.cpp

// 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
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// 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
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// 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
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#include "test.h"

#include <algorithm>

// This test shows collision processing and tests
// deferred body destruction.
class CollisionProcessing : public Test
{
public:
    CollisionProcessing()
    {
        // Ground body
        {
            b2EdgeShape shape;
            shape.SetTwoSided(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);
        }

        float xLo = -5.0f, xHi = 5.0f;
        float 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) override
    {
        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();
            float mass1   = body1->GetMass();
            float 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; }
};

static int testIndex = RegisterTest("Examples", "Collision Processing", CollisionProcessing::Create);