restitution.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 "test.h"

// Note: even with a restitution of 1.0, there is some energy change
// due to position correction.
class Restitution : public Test
{
public:

        Restitution()
        {
                const float threshold = 10.0f;

                {
                        b2BodyDef bd;
                        b2Body* ground = m_world->CreateBody(&bd);

                        b2EdgeShape shape;
                        shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
                        
                        b2FixtureDef fd;
                        fd.shape = &shape;
                        fd.restitutionThreshold = threshold;
                        ground->CreateFixture(&fd);
                }

                {
                        b2CircleShape shape;
                        shape.m_radius = 1.0f;

                        b2FixtureDef fd;
                        fd.shape = &shape;
                        fd.density = 1.0f;

                        float restitution[7] = { 0.0f, 0.1f, 0.3f, 0.5f, 0.75f, 0.9f, 1.0f };

                        for (int32 i = 0; i < 7; ++i)
                        {
                                b2BodyDef bd;
                                bd.type = b2_dynamicBody;
                                bd.position.Set(-10.0f + 3.0f * i, 20.0f);

                                b2Body* body = m_world->CreateBody(&bd);

                                fd.restitution = restitution[i];
                                fd.restitutionThreshold = threshold;
                                body->CreateFixture(&fd);
                        }
                }
        }

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

static int testIndex = RegisterTest("Forces", "Restitution", Restitution::Create);