revolute_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 "settings.h"
#include "test.h"
#include "imgui/imgui.h"

class RevoluteJoint : public Test
{
public:
        RevoluteJoint()
        {
                b2Body* ground = NULL;
                {
                        b2BodyDef bd;
                        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.filter.categoryBits = 2;

                        ground->CreateFixture(&fd);
                }

                m_enableLimit = true;
                m_enableMotor = false;
                m_motorSpeed = 1.0f;

                {
                        b2PolygonShape shape;
                        shape.SetAsBox(0.25f, 3.0f, b2Vec2(0.0f, 3.0f), 0.0f);

                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;
                        bd.position.Set(-10.0f, 20.0f);
                        b2Body* body = m_world->CreateBody(&bd);
                        body->CreateFixture(&shape, 5.0f);

                        b2RevoluteJointDef jd;
                        jd.Initialize(ground, body, b2Vec2(-10.0f, 20.5f));
                        jd.motorSpeed = m_motorSpeed;
                        jd.maxMotorTorque = 10000.0f;
                        jd.enableMotor = m_enableMotor;
                        jd.lowerAngle = -0.25f * b2_pi;
                        jd.upperAngle = 0.5f * b2_pi;
                        jd.enableLimit = m_enableLimit;

                        m_joint1 = (b2RevoluteJoint*)m_world->CreateJoint(&jd);
                }

                {
                        b2CircleShape circle_shape;
                        circle_shape.m_radius = 2.0f;

                        b2BodyDef circle_bd;
                        circle_bd.type = b2_dynamicBody;
                        circle_bd.position.Set(5.0f, 30.0f);

                        b2FixtureDef fd;
                        fd.density = 5.0f;
                        fd.filter.maskBits = 1;
                        fd.shape = &circle_shape;

                        m_ball = m_world->CreateBody(&circle_bd);
                        m_ball->CreateFixture(&fd);

                        b2PolygonShape polygon_shape;
                        polygon_shape.SetAsBox(10.0f, 0.5f, b2Vec2 (-10.0f, 0.0f), 0.0f);

                        b2BodyDef polygon_bd;
                        polygon_bd.position.Set(20.0f, 10.0f);
                        polygon_bd.type = b2_dynamicBody;
                        polygon_bd.bullet = true;
                        b2Body* polygon_body = m_world->CreateBody(&polygon_bd);
                        polygon_body->CreateFixture(&polygon_shape, 2.0f);

                        b2RevoluteJointDef jd;
                        jd.Initialize(ground, polygon_body, b2Vec2(19.0f, 10.0f));
                        jd.lowerAngle = -0.25f * b2_pi;
                        jd.upperAngle = 0.0f * b2_pi;
                        jd.enableLimit = true;
                        jd.enableMotor = true;
                        jd.motorSpeed = 0.0f;
                        jd.maxMotorTorque = 10000.0f;

                        m_joint2 = (b2RevoluteJoint*)m_world->CreateJoint(&jd);
                }
        }

        void UpdateUI() override
        {
                ImGui::SetNextWindowPos(ImVec2(10.0f, 100.0f));
                ImGui::SetNextWindowSize(ImVec2(200.0f, 100.0f));
                ImGui::Begin("Joint Controls", nullptr, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize);

                if (ImGui::Checkbox("Limit", &m_enableLimit))
                {
                        m_joint1->EnableLimit(m_enableLimit);
                }

                if (ImGui::Checkbox("Motor", &m_enableMotor))
                {
                        m_joint1->EnableMotor(m_enableMotor);
                }

                if (ImGui::SliderFloat("Speed", &m_motorSpeed, -20.0f, 20.0f, "%.0f"))
                {
                        m_joint1->SetMotorSpeed(m_motorSpeed);
                }

                ImGui::End();
        }

        void Step(Settings& settings) override
        {
                Test::Step(settings);
                
                float torque1 = m_joint1->GetMotorTorque(settings.m_hertz);
                g_debugDraw.DrawString(5, m_textLine, "Motor Torque 1= %4.0f", torque1);
                m_textLine += m_textIncrement;

                float torque2 = m_joint2->GetMotorTorque(settings.m_hertz);
                g_debugDraw.DrawString(5, m_textLine, "Motor Torque 2= %4.0f", torque2);
                m_textLine += m_textIncrement;
        }

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

        b2Body* m_ball;
        b2RevoluteJoint* m_joint1;
        b2RevoluteJoint* m_joint2;
        float m_motorSpeed;
        bool m_enableMotor;
        bool m_enableLimit;
};

static int testIndex = RegisterTest("Joints", "Revolute", RevoluteJoint::Create);