axmol/tests/cpp-tests/Source/Box2DTestBed/tests/gear_joint.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"

class GearJoint : public Test
{
public:
    GearJoint()
    {
        b2Body* ground = NULL;
        {
            b2BodyDef bd;
            ground = m_world->CreateBody(&bd);

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

        {
            b2CircleShape circle1;
            circle1.m_radius = 1.0f;

            b2PolygonShape box;
            box.SetAsBox(0.5f, 5.0f);

            b2CircleShape circle2;
            circle2.m_radius = 2.0f;

            b2BodyDef bd1;
            bd1.type = b2_staticBody;
            bd1.position.Set(10.0f, 9.0f);
            b2Body* body1 = m_world->CreateBody(&bd1);
            body1->CreateFixture(&circle1, 5.0f);

            b2BodyDef bd2;
            bd2.type = b2_dynamicBody;
            bd2.position.Set(10.0f, 8.0f);
            b2Body* body2 = m_world->CreateBody(&bd2);
            body2->CreateFixture(&box, 5.0f);

            b2BodyDef bd3;
            bd3.type = b2_dynamicBody;
            bd3.position.Set(10.0f, 6.0f);
            b2Body* body3 = m_world->CreateBody(&bd3);
            body3->CreateFixture(&circle2, 5.0f);

            b2RevoluteJointDef jd1;
            jd1.Initialize(body1, body2, bd1.position);
            b2Joint* joint1 = m_world->CreateJoint(&jd1);

            b2RevoluteJointDef jd2;
            jd2.Initialize(body2, body3, bd3.position);
            b2Joint* joint2 = m_world->CreateJoint(&jd2);

            b2GearJointDef jd4;
            jd4.bodyA  = body1;
            jd4.bodyB  = body3;
            jd4.joint1 = joint1;
            jd4.joint2 = joint2;
            jd4.ratio  = circle2.m_radius / circle1.m_radius;
            m_world->CreateJoint(&jd4);
        }

        {
            b2CircleShape circle1;
            circle1.m_radius = 1.0f;

            b2CircleShape circle2;
            circle2.m_radius = 2.0f;

            b2PolygonShape box;
            box.SetAsBox(0.5f, 5.0f);

            b2BodyDef bd1;
            bd1.type = b2_dynamicBody;
            bd1.position.Set(-3.0f, 12.0f);
            b2Body* body1 = m_world->CreateBody(&bd1);
            body1->CreateFixture(&circle1, 5.0f);

            b2RevoluteJointDef jd1;
            jd1.bodyA          = ground;
            jd1.bodyB          = body1;
            jd1.localAnchorA   = ground->GetLocalPoint(bd1.position);
            jd1.localAnchorB   = body1->GetLocalPoint(bd1.position);
            jd1.referenceAngle = body1->GetAngle() - ground->GetAngle();
            m_joint1           = (b2RevoluteJoint*)m_world->CreateJoint(&jd1);

            b2BodyDef bd2;
            bd2.type = b2_dynamicBody;
            bd2.position.Set(0.0f, 12.0f);
            b2Body* body2 = m_world->CreateBody(&bd2);
            body2->CreateFixture(&circle2, 5.0f);

            b2RevoluteJointDef jd2;
            jd2.Initialize(ground, body2, bd2.position);
            m_joint2 = (b2RevoluteJoint*)m_world->CreateJoint(&jd2);

            b2BodyDef bd3;
            bd3.type = b2_dynamicBody;
            bd3.position.Set(2.5f, 12.0f);
            b2Body* body3 = m_world->CreateBody(&bd3);
            body3->CreateFixture(&box, 5.0f);

            b2PrismaticJointDef jd3;
            jd3.Initialize(ground, body3, bd3.position, b2Vec2(0.0f, 1.0f));
            jd3.lowerTranslation = -5.0f;
            jd3.upperTranslation = 5.0f;
            jd3.enableLimit      = true;

            m_joint3 = (b2PrismaticJoint*)m_world->CreateJoint(&jd3);

            b2GearJointDef jd4;
            jd4.bodyA  = body1;
            jd4.bodyB  = body2;
            jd4.joint1 = m_joint1;
            jd4.joint2 = m_joint2;
            jd4.ratio  = circle2.m_radius / circle1.m_radius;
            m_joint4   = (b2GearJoint*)m_world->CreateJoint(&jd4);

            b2GearJointDef jd5;
            jd5.bodyA  = body2;
            jd5.bodyB  = body3;
            jd5.joint1 = m_joint2;
            jd5.joint2 = m_joint3;
            jd5.ratio  = -1.0f / circle2.m_radius;
            m_joint5   = (b2GearJoint*)m_world->CreateJoint(&jd5);
        }
    }

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

        float ratio, value;

        ratio = m_joint4->GetRatio();
        value = m_joint1->GetJointAngle() + ratio * m_joint2->GetJointAngle();
        DrawString(5, m_textLine, "theta1 + %4.2f * theta2 = %4.2f", (float)ratio, (float)value);

        ratio = m_joint5->GetRatio();
        value = m_joint2->GetJointAngle() + ratio * m_joint3->GetJointTranslation();
        DrawString(5, m_textLine, "theta2 + %4.2f * delta = %4.2f", (float)ratio, (float)value);
    }

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

    b2RevoluteJoint* m_joint1;
    b2RevoluteJoint* m_joint2;
    b2PrismaticJoint* m_joint3;
    b2GearJoint* m_joint4;
    b2GearJoint* m_joint5;
};

static int testIndex = RegisterTest("Joints", "Gear", GearJoint::Create);