mirror of https://github.com/axmolengine/axmol.git
146 lines
4.3 KiB
C++
146 lines
4.3 KiB
C++
/*
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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
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