car.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"

// This is a fun demo that shows off the wheel joint
class Car : public Test
{
public:
        Car()
        {               
                m_speed = 50.0f;

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

                        b2EdgeShape shape;

                        b2FixtureDef fd;
                        fd.shape = &shape;
                        fd.density = 0.0f;
                        fd.friction = 0.6f;

                        shape.SetTwoSided(b2Vec2(-20.0f, 0.0f), b2Vec2(20.0f, 0.0f));
                        ground->CreateFixture(&fd);

                        float hs[10] = {0.25f, 1.0f, 4.0f, 0.0f, 0.0f, -1.0f, -2.0f, -2.0f, -1.25f, 0.0f};

                        float x = 20.0f, y1 = 0.0f, dx = 5.0f;

                        for (int32 i = 0; i < 10; ++i)
                        {
                                float y2 = hs[i];
                                shape.SetTwoSided(b2Vec2(x, y1), b2Vec2(x + dx, y2));
                                ground->CreateFixture(&fd);
                                y1 = y2;
                                x += dx;
                        }

                        for (int32 i = 0; i < 10; ++i)
                        {
                                float y2 = hs[i];
                                shape.SetTwoSided(b2Vec2(x, y1), b2Vec2(x + dx, y2));
                                ground->CreateFixture(&fd);
                                y1 = y2;
                                x += dx;
                        }

                        shape.SetTwoSided(b2Vec2(x, 0.0f), b2Vec2(x + 40.0f, 0.0f));
                        ground->CreateFixture(&fd);

                        x += 80.0f;
                        shape.SetTwoSided(b2Vec2(x, 0.0f), b2Vec2(x + 40.0f, 0.0f));
                        ground->CreateFixture(&fd);

                        x += 40.0f;
                        shape.SetTwoSided(b2Vec2(x, 0.0f), b2Vec2(x + 10.0f, 5.0f));
                        ground->CreateFixture(&fd);

                        x += 20.0f;
                        shape.SetTwoSided(b2Vec2(x, 0.0f), b2Vec2(x + 40.0f, 0.0f));
                        ground->CreateFixture(&fd);

                        x += 40.0f;
                        shape.SetTwoSided(b2Vec2(x, 0.0f), b2Vec2(x, 20.0f));
                        ground->CreateFixture(&fd);
                }

                // Teeter
                {
                        b2BodyDef bd;
                        bd.position.Set(140.0f, 1.0f);
                        bd.type = b2_dynamicBody;
                        b2Body* body = m_world->CreateBody(&bd);

                        b2PolygonShape box;
                        box.SetAsBox(10.0f, 0.25f);
                        body->CreateFixture(&box, 1.0f);

                        b2RevoluteJointDef jd;
                        jd.Initialize(ground, body, body->GetPosition());
                        jd.lowerAngle = -8.0f * b2_pi / 180.0f;
                        jd.upperAngle = 8.0f * b2_pi / 180.0f;
                        jd.enableLimit = true;
                        m_world->CreateJoint(&jd);

                        body->ApplyAngularImpulse(100.0f, true);
                }

                // Bridge
                {
                        int32 N = 20;
                        b2PolygonShape shape;
                        shape.SetAsBox(1.0f, 0.125f);

                        b2FixtureDef fd;
                        fd.shape = &shape;
                        fd.density = 1.0f;
                        fd.friction = 0.6f;

                        b2RevoluteJointDef jd;

                        b2Body* prevBody = ground;
                        for (int32 i = 0; i < N; ++i)
                        {
                                b2BodyDef bd;
                                bd.type = b2_dynamicBody;
                                bd.position.Set(161.0f + 2.0f * i, -0.125f);
                                b2Body* body = m_world->CreateBody(&bd);
                                body->CreateFixture(&fd);

                                b2Vec2 anchor(160.0f + 2.0f * i, -0.125f);
                                jd.Initialize(prevBody, body, anchor);
                                m_world->CreateJoint(&jd);

                                prevBody = body;
                        }

                        b2Vec2 anchor(160.0f + 2.0f * N, -0.125f);
                        jd.Initialize(prevBody, ground, anchor);
                        m_world->CreateJoint(&jd);
                }

                // Boxes
                {
                        b2PolygonShape box;
                        box.SetAsBox(0.5f, 0.5f);

                        b2Body* body = NULL;
                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;

                        bd.position.Set(230.0f, 0.5f);
                        body = m_world->CreateBody(&bd);
                        body->CreateFixture(&box, 0.5f);

                        bd.position.Set(230.0f, 1.5f);
                        body = m_world->CreateBody(&bd);
                        body->CreateFixture(&box, 0.5f);

                        bd.position.Set(230.0f, 2.5f);
                        body = m_world->CreateBody(&bd);
                        body->CreateFixture(&box, 0.5f);

                        bd.position.Set(230.0f, 3.5f);
                        body = m_world->CreateBody(&bd);
                        body->CreateFixture(&box, 0.5f);

                        bd.position.Set(230.0f, 4.5f);
                        body = m_world->CreateBody(&bd);
                        body->CreateFixture(&box, 0.5f);
                }

                // Car
                {
                        b2PolygonShape chassis;
                        b2Vec2 vertices[8];
                        vertices[0].Set(-1.5f, -0.5f);
                        vertices[1].Set(1.5f, -0.5f);
                        vertices[2].Set(1.5f, 0.0f);
                        vertices[3].Set(0.0f, 0.9f);
                        vertices[4].Set(-1.15f, 0.9f);
                        vertices[5].Set(-1.5f, 0.2f);
                        chassis.Set(vertices, 6);

                        b2CircleShape circle;
                        circle.m_radius = 0.4f;

                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;
                        bd.position.Set(0.0f, 1.0f);
                        m_car = m_world->CreateBody(&bd);
                        m_car->CreateFixture(&chassis, 1.0f);

                        b2FixtureDef fd;
                        fd.shape = &circle;
                        fd.density = 1.0f;
                        fd.friction = 0.9f;

                        bd.position.Set(-1.0f, 0.35f);
                        m_wheel1 = m_world->CreateBody(&bd);
                        m_wheel1->CreateFixture(&fd);

                        bd.position.Set(1.0f, 0.4f);
                        m_wheel2 = m_world->CreateBody(&bd);
                        m_wheel2->CreateFixture(&fd);

                        b2WheelJointDef jd;
                        b2Vec2 axis(0.0f, 1.0f);

                        float mass1 = m_wheel1->GetMass();
                        float mass2 = m_wheel2->GetMass();

                        float hertz = 4.0f;
                        float dampingRatio = 0.7f;
                        float omega = 2.0f * b2_pi * hertz;

                        jd.Initialize(m_car, m_wheel1, m_wheel1->GetPosition(), axis);
                        jd.motorSpeed = 0.0f;
                        jd.maxMotorTorque = 20.0f;
                        jd.enableMotor = true;
                        jd.stiffness = mass1 * omega * omega;
                        jd.damping = 2.0f * mass1 * dampingRatio * omega;
                        jd.lowerTranslation = -0.25f;
                        jd.upperTranslation = 0.25f;
                        jd.enableLimit = true;
                        m_spring1 = (b2WheelJoint*)m_world->CreateJoint(&jd);

                        jd.Initialize(m_car, m_wheel2, m_wheel2->GetPosition(), axis);
                        jd.motorSpeed = 0.0f;
                        jd.maxMotorTorque = 10.0f;
                        jd.enableMotor = false;
                        jd.stiffness = mass2 * omega * omega;
                        jd.damping = 2.0f * mass2 * dampingRatio * omega;
                        jd.lowerTranslation = -0.25f;
                        jd.upperTranslation = 0.25f;
                        jd.enableLimit = true;
                        m_spring2 = (b2WheelJoint*)m_world->CreateJoint(&jd);
                }
        }

        void Keyboard(int key) override
        {
                switch (key)
                {
                case GLFW_KEY_A:
                        m_spring1->SetMotorSpeed(m_speed);
                        break;

                case GLFW_KEY_S:
                        m_spring1->SetMotorSpeed(0.0f);
                        break;

                case GLFW_KEY_D:
                        m_spring1->SetMotorSpeed(-m_speed);
                        break;
                }
        }

        void Step(Settings& settings) override
        {
                g_debugDraw.DrawString(5, m_textLine, "Keys: left = a, brake = s, right = d, hz down = q, hz up = e");
                m_textLine += m_textIncrement;

                g_camera.m_center.x = m_car->GetPosition().x;
                Test::Step(settings);
        }

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

        b2Body* m_car;
        b2Body* m_wheel1;
        b2Body* m_wheel2;

        float m_speed;
        b2WheelJoint* m_spring1;
        b2WheelJoint* m_spring2;
};

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