distance_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"
#include "imgui/imgui.h"

// This tests distance joints, body destruction, and joint destruction.
class DistanceJoint : public Test
{
public:
        DistanceJoint()
        {
                b2Body* ground = NULL;
                {
                        b2BodyDef bd;
                        ground = m_world->CreateBody(&bd);

                        b2EdgeShape shape;
                        shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
                        ground->CreateFixture(&shape, 0.0f);
                }

                {
                        b2BodyDef bd;
                        bd.type = b2_dynamicBody;
                        bd.angularDamping = 0.1f;

                        bd.position.Set(0.0f, 5.0f);
                        b2Body* body = m_world->CreateBody(&bd);

                        b2PolygonShape shape;
                        shape.SetAsBox(0.5f, 0.5f);
                        body->CreateFixture(&shape, 5.0f);

                        m_hertz = 1.0f;
                        m_dampingRatio = 0.7f;

                        b2DistanceJointDef jd;
                        jd.Initialize(ground, body, b2Vec2(0.0f, 15.0f), bd.position);
                        jd.collideConnected = true;
                        m_length = jd.length;
                        m_minLength = m_length;
                        m_maxLength = m_length;
                        b2LinearStiffness(jd.stiffness, jd.damping, m_hertz, m_dampingRatio, jd.bodyA, jd.bodyB);
                        m_joint = (b2DistanceJoint*)m_world->CreateJoint(&jd);
                }
        }

        void UpdateUI() override
        {
                ImGui::SetNextWindowPos(ImVec2(10.0f, 100.0f));
                ImGui::SetNextWindowSize(ImVec2(260.0f, 150.0f));
                ImGui::Begin("Joint Controls", nullptr, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize);

                if (ImGui::SliderFloat("Length", &m_length, 0.0f, 20.0f, "%.0f"))
                {
                        m_length = m_joint->SetLength(m_length);
                }

                if (ImGui::SliderFloat("Min Length", &m_minLength, 0.0f, 20.0f, "%.0f"))
                {
                        m_minLength = m_joint->SetMinLength(m_minLength);
                }

                if (ImGui::SliderFloat("Max Length", &m_maxLength, 0.0f, 20.0f, "%.0f"))
                {
                        m_maxLength = m_joint->SetMaxLength(m_maxLength);
                }

                if (ImGui::SliderFloat("Hertz", &m_hertz, 0.0f, 10.0f, "%.1f"))
                {
                        float stiffness;
                        float damping;
                        b2LinearStiffness(stiffness, damping, m_hertz, m_dampingRatio, m_joint->GetBodyA(), m_joint->GetBodyB());
                        m_joint->SetStiffness(stiffness);
                        m_joint->SetDamping(damping);
                }

                if (ImGui::SliderFloat("Damping Ratio", &m_dampingRatio, 0.0f, 2.0f, "%.1f"))
                {
                        float stiffness;
                        float damping;
                        b2LinearStiffness(stiffness, damping, m_hertz, m_dampingRatio, m_joint->GetBodyA(), m_joint->GetBodyB());
                        m_joint->SetStiffness(stiffness);
                        m_joint->SetDamping(damping);
                }

                ImGui::End();
        }

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

        b2DistanceJoint* m_joint;
        float m_length;
        float m_minLength;
        float m_maxLength;
        float m_hertz;
        float m_dampingRatio;
};

static int testIndex = RegisterTest("Joints", "Distance Joint", DistanceJoint::Create);