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Viewing changes to tests/box2d/Testbed/Tests/RopeJoint.h

  • Committer: Package Import Robot
  • Author(s): Sylvestre Ledru
  • Date: 2013-05-02 13:11:51 UTC
  • Revision ID: package-import@ubuntu.com-20130502131151-q8dvteqr1ef2x7xz
Tags: upstream-1.4.1~20130504~adb56cb
Import upstream version 1.4.1~20130504~adb56cb

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tests/box2d/Testbed/Tests/RopeJoint.h
 
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/*
 
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* Copyright (c) 2006-2010 Erin Catto http://www.box2d.org
 
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*
 
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* This software is provided 'as-is', without any express or implied
 
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* warranty.  In no event will the authors be held liable for any damages
 
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* arising from the use of this software.
 
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* Permission is granted to anyone to use this software for any purpose,
 
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* including commercial applications, and to alter it and redistribute it
 
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* freely, subject to the following restrictions:
 
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* 1. The origin of this software must not be misrepresented; you must not
 
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* claim that you wrote the original software. If you use this software
 
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* in a product, an acknowledgment in the product documentation would be
 
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* appreciated but is not required.
 
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* 2. Altered source versions must be plainly marked as such, and must not be
 
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* misrepresented as being the original software.
 
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* 3. This notice may not be removed or altered from any source distribution.
 
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*/
 
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#ifndef ROPE_JOINT_H
 
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#define ROPE_JOINT_H
 
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/// This test shows how a rope joint can be used to stabilize a chain of
 
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/// bodies with a heavy payload. Notice that the rope joint just prevents
 
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/// excessive stretching and has no other effect.
 
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/// By disabling the rope joint you can see that the Box2D solver has trouble
 
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/// supporting heavy bodies with light bodies. Try playing around with the
 
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/// densities, time step, and iterations to see how they affect stability.
 
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/// This test also shows how to use contact filtering. Filtering is configured
 
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/// so that the payload does not collide with the chain.
 
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class RopeJoint : public Test
 
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{
 
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public:
 
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        RopeJoint()
 
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        {
 
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                b2Body* ground = NULL;
 
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                {
 
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                        b2BodyDef bd;
 
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                        ground = m_world->CreateBody(&bd);
 
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                        b2EdgeShape shape;
 
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                        shape.Set(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
 
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                        ground->CreateFixture(&shape, 0.0f);
 
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                }
 
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                {
 
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                        b2PolygonShape shape;
 
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                        shape.SetAsBox(0.5f, 0.125f);
 
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                        b2FixtureDef fd;
 
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                        fd.shape = &shape;
 
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                        fd.density = 20.0f;
 
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                        fd.friction = 0.2f;
 
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                        fd.filter.categoryBits = 0x0001;
 
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                        fd.filter.maskBits = 0xFFFF & ~0x0002;
 
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                        b2RevoluteJointDef jd;
 
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                        jd.collideConnected = false;
 
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                        const int32 N = 10;
 
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                        const float32 y = 15.0f;
 
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                        m_ropeDef.localAnchorA.Set(0.0f, y);
 
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                        b2Body* prevBody = ground;
 
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                        for (int32 i = 0; i < N; ++i)
 
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                        {
 
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                                b2BodyDef bd;
 
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                                bd.type = b2_dynamicBody;
 
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                                bd.position.Set(0.5f + 1.0f * i, y);
 
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                                if (i == N - 1)
 
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                                {
 
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                                        shape.SetAsBox(1.5f, 1.5f);
 
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                                        fd.density = 100.0f;
 
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                                        fd.filter.categoryBits = 0x0002;
 
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                                        bd.position.Set(1.0f * i, y);
 
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                                        bd.angularDamping = 0.4f;
 
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                                }
 
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                                b2Body* body = m_world->CreateBody(&bd);
 
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                                body->CreateFixture(&fd);
 
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                                b2Vec2 anchor(float32(i), y);
 
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                                jd.Initialize(prevBody, body, anchor);
 
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                                m_world->CreateJoint(&jd);
 
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                                prevBody = body;
 
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                        }
 
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                        m_ropeDef.localAnchorB.SetZero();
 
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                        float32 extraLength = 0.01f;
 
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                        m_ropeDef.maxLength = N - 1.0f + extraLength;
 
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                        m_ropeDef.bodyB = prevBody;
 
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                }
 
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                {
 
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                        m_ropeDef.bodyA = ground;
 
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                        m_rope = m_world->CreateJoint(&m_ropeDef);
 
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                }
 
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        }
 
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        void Keyboard(unsigned char key)
 
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        {
 
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                switch (key)
 
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                {
 
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                case 'j':
 
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                        if (m_rope)
 
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                        {
 
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                                m_world->DestroyJoint(m_rope);
 
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                                m_rope = NULL;
 
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                        }
 
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                        else
 
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                        {
 
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                                m_rope = m_world->CreateJoint(&m_ropeDef);
 
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                        }
 
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                        break;
 
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                }
 
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        }
 
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        void Step(Settings* settings)
 
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        {
 
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                Test::Step(settings);
 
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                m_debugDraw.DrawString(5, m_textLine, "Press (j) to toggle the rope joint.");
 
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                m_textLine += 15;
 
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                if (m_rope)
 
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                {
 
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                        m_debugDraw.DrawString(5, m_textLine, "Rope ON");
 
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                }
 
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                else
 
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                {
 
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                        m_debugDraw.DrawString(5, m_textLine, "Rope OFF");
 
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                }
 
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                m_textLine += 15;
 
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        }
 
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        static Test* Create()
 
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        {
 
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                return new RopeJoint;
 
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        }
 
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        b2RopeJointDef m_ropeDef;
 
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        b2Joint* m_rope;
 
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};
 
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#endif