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);