theo_jansen.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.

// Inspired by a contribution from roman_m
// Dimensions scooped from APE (http://www.cove.org/ape/index.htm)

#include "test.h"

class TheoJansen : public Test
{
public:

        void CreateLeg(float s, const b2Vec2& wheelAnchor)
        {
                b2Vec2 p1(5.4f * s, -6.1f);
                b2Vec2 p2(7.2f * s, -1.2f);
                b2Vec2 p3(4.3f * s, -1.9f);
                b2Vec2 p4(3.1f * s, 0.8f);
                b2Vec2 p5(6.0f * s, 1.5f);
                b2Vec2 p6(2.5f * s, 3.7f);

                b2FixtureDef fd1, fd2;
                fd1.filter.groupIndex = -1;
                fd2.filter.groupIndex = -1;
                fd1.density = 1.0f;
                fd2.density = 1.0f;

                b2PolygonShape poly1, poly2;

                if (s > 0.0f)
                {
                        b2Vec2 vertices[3];

                        vertices[0] = p1;
                        vertices[1] = p2;
                        vertices[2] = p3;
                        poly1.Set(vertices, 3);

                        vertices[0] = b2Vec2_zero;
                        vertices[1] = p5 - p4;
                        vertices[2] = p6 - p4;
                        poly2.Set(vertices, 3);
                }
                else
                {
                        b2Vec2 vertices[3];

                        vertices[0] = p1;
                        vertices[1] = p3;
                        vertices[2] = p2;
                        poly1.Set(vertices, 3);

                        vertices[0] = b2Vec2_zero;
                        vertices[1] = p6 - p4;
                        vertices[2] = p5 - p4;
                        poly2.Set(vertices, 3);
                }

                fd1.shape = &poly1;
                fd2.shape = &poly2;

                b2BodyDef bd1, bd2;
                bd1.type = b2_dynamicBody;
                bd2.type = b2_dynamicBody;
                bd1.position = m_offset;
                bd2.position = p4 + m_offset;

                bd1.angularDamping = 10.0f;
                bd2.angularDamping = 10.0f;

                b2Body* body1 = m_world->CreateBody(&bd1);
                b2Body* body2 = m_world->CreateBody(&bd2);

                body1->CreateFixture(&fd1);
                body2->CreateFixture(&fd2);

                {
                        b2DistanceJointDef jd;

                        // Using a soft distance constraint can reduce some jitter.
                        // It also makes the structure seem a bit more fluid by
                        // acting like a suspension system.
                        float dampingRatio = 0.5f;
                        float frequencyHz = 10.0f;

                        jd.Initialize(body1, body2, p2 + m_offset, p5 + m_offset);
                        b2LinearStiffness(jd.stiffness, jd.damping, frequencyHz, dampingRatio, jd.bodyA, jd.bodyB);
                        m_world->CreateJoint(&jd);

                        jd.Initialize(body1, body2, p3 + m_offset, p4 + m_offset);
                        b2LinearStiffness(jd.stiffness, jd.damping, frequencyHz, dampingRatio, jd.bodyA, jd.bodyB);
                        m_world->CreateJoint(&jd);

                        jd.Initialize(body1, m_wheel, p3 + m_offset, wheelAnchor + m_offset);
                        b2LinearStiffness(jd.stiffness, jd.damping, frequencyHz, dampingRatio, jd.bodyA, jd.bodyB);
                        m_world->CreateJoint(&jd);

                        jd.Initialize(body2, m_wheel, p6 + m_offset, wheelAnchor + m_offset);
                        b2LinearStiffness(jd.stiffness, jd.damping, frequencyHz, dampingRatio, jd.bodyA, jd.bodyB);
                        m_world->CreateJoint(&jd);
                }

                {
                        b2RevoluteJointDef jd;
                        jd.Initialize(body2, m_chassis, p4 + m_offset);
                        m_world->CreateJoint(&jd);
                }
        }

        TheoJansen()
        {
                m_offset.Set(0.0f, 8.0f);
                m_motorSpeed = 2.0f;
                m_motorOn = true;
                b2Vec2 pivot(0.0f, 0.8f);

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

                        b2EdgeShape shape;
                        shape.SetTwoSided(b2Vec2(-50.0f, 0.0f), b2Vec2(50.0f, 0.0f));
                        ground->CreateFixture(&shape, 0.0f);

                        shape.SetTwoSided(b2Vec2(-50.0f, 0.0f), b2Vec2(-50.0f, 10.0f));
                        ground->CreateFixture(&shape, 0.0f);

                        shape.SetTwoSided(b2Vec2(50.0f, 0.0f), b2Vec2(50.0f, 10.0f));
                        ground->CreateFixture(&shape, 0.0f);
                }

                // Balls
                for (int32 i = 0; i < 40; ++i)
                {
                        b2CircleShape shape;
                        shape.m_radius = 0.25f;

                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;
                        bd.position.Set(-40.0f + 2.0f * i, 0.5f);

                        b2Body* body = m_world->CreateBody(&bd);
                        body->CreateFixture(&shape, 1.0f);
                }

                // Chassis
                {
                        b2PolygonShape shape;
                        shape.SetAsBox(2.5f, 1.0f);

                        b2FixtureDef sd;
                        sd.density = 1.0f;
                        sd.shape = &shape;
                        sd.filter.groupIndex = -1;
                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;
                        bd.position = pivot + m_offset;
                        m_chassis = m_world->CreateBody(&bd);
                        m_chassis->CreateFixture(&sd);
                }

                {
                        b2CircleShape shape;
                        shape.m_radius = 1.6f;

                        b2FixtureDef sd;
                        sd.density = 1.0f;
                        sd.shape = &shape;
                        sd.filter.groupIndex = -1;
                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;
                        bd.position = pivot + m_offset;
                        m_wheel = m_world->CreateBody(&bd);
                        m_wheel->CreateFixture(&sd);
                }

                {
                        b2RevoluteJointDef jd;
                        jd.Initialize(m_wheel, m_chassis, pivot + m_offset);
                        jd.collideConnected = false;
                        jd.motorSpeed = m_motorSpeed;
                        jd.maxMotorTorque = 400.0f;
                        jd.enableMotor = m_motorOn;
                        m_motorJoint = (b2RevoluteJoint*)m_world->CreateJoint(&jd);
                }

                b2Vec2 wheelAnchor;
                
                wheelAnchor = pivot + b2Vec2(0.0f, -0.8f);

                CreateLeg(-1.0f, wheelAnchor);
                CreateLeg(1.0f, wheelAnchor);

                m_wheel->SetTransform(m_wheel->GetPosition(), 120.0f * b2_pi / 180.0f);
                CreateLeg(-1.0f, wheelAnchor);
                CreateLeg(1.0f, wheelAnchor);

                m_wheel->SetTransform(m_wheel->GetPosition(), -120.0f * b2_pi / 180.0f);
                CreateLeg(-1.0f, wheelAnchor);
                CreateLeg(1.0f, wheelAnchor);
        }

        void Step(Settings& settings) override
        {
                g_debugDraw.DrawString(5, m_textLine, "Keys: left = a, brake = s, right = d, toggle motor = m");
                m_textLine += m_textIncrement;

                Test::Step(settings);
        }

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

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

                case GLFW_KEY_D:
                        m_motorJoint->SetMotorSpeed(m_motorSpeed);
                        break;

                case GLFW_KEY_M:
                        m_motorJoint->EnableMotor(!m_motorJoint->IsMotorEnabled());
                        break;
                }
        }

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

        b2Vec2 m_offset;
        b2Body* m_chassis;
        b2Body* m_wheel;
        b2RevoluteJoint* m_motorJoint;
        bool m_motorOn;
        float m_motorSpeed;
};

static int testIndex = RegisterTest("Examples", "Theo Jansen", TheoJansen::Create);