Add btGearConstraint, with a demo in Bullet/Demos/ConstraintDemo

Thanks to Dimitris Papavasiliou for the idea.

Demos/ConstraintDemo/ConstraintDemo.cpp

@@ -28,6 +28,10 @@ subject to the following restrictions:
 #include "GL_ShapeDrawer.h"
 #include "GlutStuff.h"
 
+#include "GLDebugDrawer.h"
+static GLDebugDrawer	gDebugDrawer;
+
+
 
 const int numObjects = 3;
 
@@ -85,6 +89,11 @@ void	ConstraintDemo::setupEmptyDynamicsWorld()
 
 }
 
+void	ConstraintDemo::clientResetScene()
+{
+	exitPhysics();
+	initPhysics();
+}
 void	ConstraintDemo::initPhysics()
 {
 	setTexturing(true);
@@ -95,6 +104,9 @@ void	ConstraintDemo::initPhysics()
 
 	setupEmptyDynamicsWorld();
 
+	m_dynamicsWorld->setDebugDrawer(&gDebugDrawer);
+
+
 	//btCollisionShape* groundShape = new btBoxShape(btVector3(btScalar(50.),btScalar(40.),btScalar(50.)));
 	btCollisionShape* groundShape = new btStaticPlaneShape(btVector3(0,1,0),40);
 
@@ -115,6 +127,76 @@ void	ConstraintDemo::initPhysics()
 
 	float mass = 1.f;
 
+#if ENABLE_ALL_DEMOS
+///gear constraint demo
+
+#define THETA SIMD_PI/4.f
+#define L_1 (2 - tan(THETA))
+#define L_2 (1 / cos(THETA))
+#define RATIO L_2 / L_1
+
+	btRigidBody* bodyA=0;
+	btRigidBody* bodyB=0;
+
+	{
+		btCollisionShape* cylA = new btCylinderShape(btVector3(0.2,0.25,0.2));
+		btCollisionShape* cylB = new btCylinderShape(btVector3(L_1,0.025,L_1));
+		btCompoundShape* cyl0 = new btCompoundShape();
+		cyl0->addChildShape(btTransform::getIdentity(),cylA);
+		cyl0->addChildShape(btTransform::getIdentity(),cylB);
+
+		btScalar mass = 6.28;
+		btVector3 localInertia;
+		cyl0->calculateLocalInertia(mass,localInertia);
+		btRigidBody::btRigidBodyConstructionInfo ci(mass,0,cyl0,localInertia);
+		ci.m_startWorldTransform.setOrigin(btVector3(-8,1,-8));
+
+		btRigidBody* body = new btRigidBody(ci);//1,0,cyl0,localInertia);
+		m_dynamicsWorld->addRigidBody(body);
+		body->setLinearFactor(btVector3(0,0,0));
+		body->setAngularFactor(btVector3(0,1,0));
+		bodyA = body;
+	}
+
+	{
+		btCollisionShape* cylA = new btCylinderShape(btVector3(0.2,0.26,0.2));
+		btCollisionShape* cylB = new btCylinderShape(btVector3(L_2,0.025,L_2));
+		btCompoundShape* cyl0 = new btCompoundShape();
+		cyl0->addChildShape(btTransform::getIdentity(),cylA);
+		cyl0->addChildShape(btTransform::getIdentity(),cylB);
+
+		btScalar mass = 6.28;
+		btVector3 localInertia;
+		cyl0->calculateLocalInertia(mass,localInertia);
+		btRigidBody::btRigidBodyConstructionInfo ci(mass,0,cyl0,localInertia);
+		ci.m_startWorldTransform.setOrigin(btVector3(-10,2,-8));
+
+
+		btQuaternion orn(btVector3(0,0,1),-THETA);
+		ci.m_startWorldTransform.setRotation(orn);
+
+		btRigidBody* body = new btRigidBody(ci);//1,0,cyl0,localInertia);
+		body->setLinearFactor(btVector3(0,0,0));
+		btHingeConstraint* hinge = new btHingeConstraint(*body,btVector3(0,0,0),btVector3(0,1,0),true);
+		m_dynamicsWorld->addConstraint(hinge);
+		bodyB= body;
+		body->setAngularVelocity(btVector3(0,3,0));
+
+		m_dynamicsWorld->addRigidBody(body);
+	}
+
+	btVector3	axisA(0,1,0);
+	btVector3	axisB(0,1,0);
+	btQuaternion orn(btVector3(0,0,1),-THETA);
+	btMatrix3x3 mat(orn);
+	axisB = mat.getRow(1);
+
+	btGearConstraint* gear = new btGearConstraint(*bodyA,*bodyB, axisA,axisB,RATIO);
+	m_dynamicsWorld->addConstraint(gear,true);
+
+
+#endif
+
 
 #if ENABLE_ALL_DEMOS
 	//point to point constraint with a breaking threshold

Demos/ConstraintDemo/ConstraintDemo.h

@@ -39,6 +39,9 @@ class ConstraintDemo : public PlatformDemoApplication
 
 	void	setupEmptyDynamicsWorld();
 
+	void	clientResetScene();
+
+
 	public:
 
 

Demos/ConstraintDemo/main.cpp

@@ -1,18 +1,18 @@
 #include "ConstraintDemo.h"
 #include "GlutStuff.h"
 #include "GLDebugDrawer.h"
+
 #include "btBulletDynamicsCommon.h"
 
 int main(int argc,char** argv)
 {
 
-	GLDebugDrawer	gDebugDrawer;
+	
 
     ConstraintDemo* constraintDemo = new ConstraintDemo();
 	
 
     constraintDemo->initPhysics();
-	constraintDemo->getDynamicsWorld()->setDebugDrawer(&gDebugDrawer);
 	constraintDemo->setDebugMode(btIDebugDraw::DBG_DrawConstraints+btIDebugDraw::DBG_DrawConstraintLimits);
 	
 	return glutmain(argc, argv,640,480,"Constraint Demo. http://www.continuousphysics.com/Bullet/phpBB2/",constraintDemo);

src/BulletDynamics/CMakeLists.txt

@@ -6,6 +6,7 @@ SET(BulletDynamics_SRCS
 	Character/btKinematicCharacterController.cpp
 	ConstraintSolver/btConeTwistConstraint.cpp
 	ConstraintSolver/btContactConstraint.cpp
+	ConstraintSolver/btGearConstraint.cpp
 	ConstraintSolver/btGeneric6DofConstraint.cpp
 	ConstraintSolver/btGeneric6DofSpringConstraint.cpp
 	ConstraintSolver/btHinge2Constraint.cpp
@@ -33,6 +34,7 @@ SET(ConstraintSolver_HDRS
 	ConstraintSolver/btConstraintSolver.h
 	ConstraintSolver/btContactConstraint.h
 	ConstraintSolver/btContactSolverInfo.h
+	ConstraintSolver/btGearConstraint.h
 	ConstraintSolver/btGeneric6DofConstraint.h
 	ConstraintSolver/btGeneric6DofSpringConstraint.h
 	ConstraintSolver/btHinge2Constraint.h

src/BulletDynamics/ConstraintSolver/btGearConstraint.cpp

@@ -0,0 +1,54 @@
+/*
+Bullet Continuous Collision Detection and Physics Library
+Copyright (c) 2012 Advanced Micro Devices, Inc.  http://bulletphysics.org
+
+This software is provided 'as-is', without any express or implied warranty.
+In no event will the authors be held liable for any damages arising from the use of this software.
+Permission is granted to anyone to use this software for any purpose, 
+including commercial applications, and to alter it and redistribute it freely, 
+subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+*/
+
+/// Implemented by Erwin Coumans. The idea for the constraint comes from Dimitris Papavasiliou.
+
+#include "btGearConstraint.h"
+
+btGearConstraint::btGearConstraint(btRigidBody& rbA, btRigidBody& rbB, const btVector3& axisInA,const btVector3& axisInB, btScalar ratio)
+:btTypedConstraint(GEAR_CONSTRAINT_TYPE,rbA,rbB),
+m_axisInA(axisInA),
+m_axisInB(axisInB),
+m_ratio(ratio)
+{
+}
+
+btGearConstraint::~btGearConstraint ()
+{
+}
+
+void btGearConstraint::getInfo1 (btConstraintInfo1* info)
+{
+	info->m_numConstraintRows = 1;
+	info->nub = 1;
+}
+
+void btGearConstraint::getInfo2 (btConstraintInfo2* info)
+{
+	btVector3 globalAxisA, globalAxisB;
+
+	globalAxisA = m_rbA.getWorldTransform().getBasis()*this->m_axisInA;
+	globalAxisB = m_rbB.getWorldTransform().getBasis()*this->m_axisInB;
+
+	info->m_J1angularAxis[0] = globalAxisA[0];
+	info->m_J1angularAxis[1] = globalAxisA[1];
+	info->m_J1angularAxis[2] = globalAxisA[2];
+
+	info->m_J2angularAxis[0] = m_ratio*globalAxisB[0];
+	info->m_J2angularAxis[1] = m_ratio*globalAxisB[1];
+	info->m_J2angularAxis[2] = m_ratio*globalAxisB[2];
+
+}
+

src/BulletDynamics/ConstraintSolver/btGearConstraint.h

@@ -0,0 +1,56 @@
+/*
+Bullet Continuous Collision Detection and Physics Library
+Copyright (c) 2012 Advanced Micro Devices, Inc.  http://bulletphysics.org
+
+This software is provided 'as-is', without any express or implied warranty.
+In no event will the authors be held liable for any damages arising from the use of this software.
+Permission is granted to anyone to use this software for any purpose, 
+including commercial applications, and to alter it and redistribute it freely, 
+subject to the following restrictions:
+
+1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+3. This notice may not be removed or altered from any source distribution.
+*/
+
+
+
+#ifndef BT_GEAR_CONSTRAINT_H
+#define BT_GEAR_CONSTRAINT_H
+
+#include "BulletDynamics/ConstraintSolver/btTypedConstraint.h"
+///The btGeatConstraint will couple the angular velocity for two bodies around given local axis and ratio.
+///See Bullet/Demos/ConstraintDemo for an example use.
+class btGearConstraint : public btTypedConstraint
+{
+protected:
+	btVector3	m_axisInA;
+	btVector3	m_axisInB;
+	bool		m_useFrameA;
+	btScalar	m_ratio;
+
+public:
+	btGearConstraint(btRigidBody& rbA, btRigidBody& rbB, const btVector3& axisInA,const btVector3& axisInB, btScalar ratio=1.f);
+	virtual ~btGearConstraint ();
+
+	///internal method used by the constraint solver, don't use them directly
+	virtual void getInfo1 (btConstraintInfo1* info);
+
+	///internal method used by the constraint solver, don't use them directly
+	virtual void getInfo2 (btConstraintInfo2* info);
+
+	virtual	void	setParam(int num, btScalar value, int axis = -1) 
+	{
+		btAssert(0);
+	};
+
+	///return the local value of parameter
+	virtual	btScalar getParam(int num, int axis = -1) const 
+	{ 
+		btAssert(0);
+		return 0.f;
+	}
+
+};
+
+#endif //BT_GEAR_CONSTRAINT_H

src/BulletDynamics/ConstraintSolver/btTypedConstraint.h

@@ -33,6 +33,7 @@ enum btTypedConstraintType
 	SLIDER_CONSTRAINT_TYPE,
 	CONTACT_CONSTRAINT_TYPE,
 	D6_SPRING_CONSTRAINT_TYPE,
+	GEAR_CONSTRAINT_TYPE,
 	MAX_CONSTRAINT_TYPE
 };
 

src/Makefile.am

@@ -313,6 +313,7 @@ libBulletDynamics_la_SOURCES = \
 		BulletDynamics/Dynamics/btSimpleDynamicsWorld.cpp \
 		BulletDynamics/Dynamics/Bullet-C-API.cpp \
 		BulletDynamics/Dynamics/btDiscreteDynamicsWorld.cpp \
+		BulletDynamics/ConstraintSolver/btGearConstraint.cpp \
 		BulletDynamics/ConstraintSolver/btGeneric6DofConstraint.cpp \
 		BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.cpp \
 		BulletDynamics/ConstraintSolver/btSolve2LinearConstraint.cpp \
@@ -345,6 +346,7 @@ libBulletDynamics_la_SOURCES = \
 		BulletDynamics/ConstraintSolver/btJacobianEntry.h \
 		BulletDynamics/ConstraintSolver/btSolverConstraint.h \
 		BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.h \
+		BulletDynamics/ConstraintSolver/btGearConstraint.h \
 		BulletDynamics/ConstraintSolver/btGeneric6DofConstraint.h \
 		BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.h \
 		BulletDynamics/ConstraintSolver/btSliderConstraint.h \
@@ -403,6 +405,7 @@ nobase_bullet_include_HEADERS += \
 	BulletDynamics/ConstraintSolver/btConstraintSolver.h \
 	BulletDynamics/ConstraintSolver/btContactConstraint.h \
 	BulletDynamics/ConstraintSolver/btContactSolverInfo.h \
+	BulletDynamics/ConstraintSolver/btGearConstraint.h \
 	BulletDynamics/ConstraintSolver/btGeneric6DofConstraint.h \
 	BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.h \
 	BulletDynamics/ConstraintSolver/btJacobianEntry.h \

src/btBulletDynamicsCommon.h

@@ -32,6 +32,7 @@ subject to the following restrictions:
 #include "BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.h"
 #include "BulletDynamics/ConstraintSolver/btUniversalConstraint.h"
 #include "BulletDynamics/ConstraintSolver/btHinge2Constraint.h"
+#include "BulletDynamics/ConstraintSolver/btGearConstraint.h"
 
 #include "BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.h"