axmol/tests/cpp-tests/Classes/Box2DTestBed/tests/breakable.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
// 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 "test.h"

// This is used to test sensor shapes.
class Breakable : public Test
{
public:
    enum
    {
        e_count = 7
    };

    Breakable()
    {
        // Ground body
        {
            b2BodyDef bd;
            b2Body* ground = m_world->CreateBody(&bd);

            b2EdgeShape shape;
            shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
            ground->CreateFixture(&shape, 0.0f);
        }

        // Breakable dynamic body
        {
            b2BodyDef bd;
            bd.type = b2_dynamicBody;
            bd.position.Set(0.0f, 40.0f);
            bd.angle = 0.25f * b2_pi;
            m_body1  = m_world->CreateBody(&bd);

            m_shape1.SetAsBox(0.5f, 0.5f, b2Vec2(-0.5f, 0.0f), 0.0f);
            m_piece1 = m_body1->CreateFixture(&m_shape1, 1.0f);

            m_shape2.SetAsBox(0.5f, 0.5f, b2Vec2(0.5f, 0.0f), 0.0f);
            m_piece2 = m_body1->CreateFixture(&m_shape2, 1.0f);
        }

        m_break = false;
        m_broke = false;
    }

    void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse) override
    {
        if (m_broke)
        {
            // The body already broke.
            return;
        }

        // Should the body break?
        int32 count = contact->GetManifold()->pointCount;

        float maxImpulse = 0.0f;
        for (int32 i = 0; i < count; ++i)
        {
            maxImpulse = b2Max(maxImpulse, impulse->normalImpulses[i]);
        }

        if (maxImpulse > 40.0f)
        {
            // Flag the body for breaking.
            m_break = true;
        }
    }

    void Break()
    {
        // Create two bodies from one.
        b2Body* body1 = m_piece1->GetBody();
        b2Vec2 center = body1->GetWorldCenter();

        body1->DestroyFixture(m_piece2);
        m_piece2 = NULL;

        b2BodyDef bd;
        bd.type     = b2_dynamicBody;
        bd.position = body1->GetPosition();
        bd.angle    = body1->GetAngle();

        b2Body* body2 = m_world->CreateBody(&bd);
        m_piece2      = body2->CreateFixture(&m_shape2, 1.0f);

        // Compute consistent velocities for new bodies based on
        // cached velocity.
        b2Vec2 center1 = body1->GetWorldCenter();
        b2Vec2 center2 = body2->GetWorldCenter();

        b2Vec2 velocity1 = m_velocity + b2Cross(m_angularVelocity, center1 - center);
        b2Vec2 velocity2 = m_velocity + b2Cross(m_angularVelocity, center2 - center);

        body1->SetAngularVelocity(m_angularVelocity);
        body1->SetLinearVelocity(velocity1);

        body2->SetAngularVelocity(m_angularVelocity);
        body2->SetLinearVelocity(velocity2);
    }

    void Step(Settings& settings) override
    {
        if (m_break)
        {
            Break();
            m_broke = true;
            m_break = false;
        }

        // Cache velocities to improve movement on breakage.
        if (m_broke == false)
        {
            m_velocity        = m_body1->GetLinearVelocity();
            m_angularVelocity = m_body1->GetAngularVelocity();
        }

        Test::Step(settings);
    }

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

    b2Body* m_body1;
    b2Vec2 m_velocity;
    float m_angularVelocity;
    b2PolygonShape m_shape1;
    b2PolygonShape m_shape2;
    b2Fixture* m_piece1;
    b2Fixture* m_piece2;

    bool m_broke;
    bool m_break;
};

static int testIndex = RegisterTest("Examples", "Breakable", Breakable::Create);