pulley_joint.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"

class PulleyJoint : public Test
{
public:
        PulleyJoint()
        {
                float y = 16.0f;
                float L = 12.0f;
                float a = 1.0f;
                float b = 2.0f;

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

                        b2CircleShape circle;
                        circle.m_radius = 2.0f;

                        circle.m_p.Set(-10.0f, y + b + L);
                        ground->CreateFixture(&circle, 0.0f);

                        circle.m_p.Set(10.0f, y + b + L);
                        ground->CreateFixture(&circle, 0.0f);
                }

                {

                        b2PolygonShape shape;
                        shape.SetAsBox(a, b);

                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;

                        //bd.fixedRotation = true;
                        bd.position.Set(-10.0f, y);
                        b2Body* body1 = m_world->CreateBody(&bd);
                        body1->CreateFixture(&shape, 5.0f);

                        bd.position.Set(10.0f, y);
                        b2Body* body2 = m_world->CreateBody(&bd);
                        body2->CreateFixture(&shape, 5.0f);

                        b2PulleyJointDef pulleyDef;
                        b2Vec2 anchor1(-10.0f, y + b);
                        b2Vec2 anchor2(10.0f, y + b);
                        b2Vec2 groundAnchor1(-10.0f, y + b + L);
                        b2Vec2 groundAnchor2(10.0f, y + b + L);
                        pulleyDef.Initialize(body1, body2, groundAnchor1, groundAnchor2, anchor1, anchor2, 1.5f);

                        m_joint1 = (b2PulleyJoint*)m_world->CreateJoint(&pulleyDef);
                }
        }

        void Step(Settings& settings) override
        {
                Test::Step(settings);

                float ratio = m_joint1->GetRatio();
                float L = m_joint1->GetCurrentLengthA() + ratio * m_joint1->GetCurrentLengthB();
                g_debugDraw.DrawString(5, m_textLine, "L1 + %4.2f * L2 = %4.2f", (float) ratio, (float) L);
                m_textLine += m_textIncrement;
        }

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

        b2PulleyJoint* m_joint1;
};

static int testIndex = RegisterTest("Joints", "Pulley", PulleyJoint::Create);