https://github.com/bulletphysics/bullet3/pull/618 by Mobeen

Summary of changes:
1) Changed include paths to be relative to the current sources (affected
files: LoadMeshFromObj.cpp, Wavefront2GLInstanceGraphicsShape.h/cpp)
2) Added new tutorials in the ExtendedTutorials folder
3) Modified the main_opengl_single_example.cpp file to enable picking
support in standalone demos

examples/ExtendedTutorials/Chain.cpp

@@ -0,0 +1,137 @@
+/*
+Bullet Continuous Collision Detection and Physics Library
+Copyright (c) 2015 Google 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.
+*/
+
+
+
+#include "Chain.h"
+
+#include "btBulletDynamicsCommon.h"
+#include "LinearMath/btVector3.h"
+#include "LinearMath/btAlignedObjectArray.h" 
+#include "../CommonInterfaces/CommonRigidBodyBase.h"
+
+const int TOTAL_BOXES = 10;
+struct ChainExample : public CommonRigidBodyBase
+{
+	ChainExample(struct GUIHelperInterface* helper)
+		:CommonRigidBodyBase(helper)
+	{
+	}
+	virtual ~ChainExample(){}
+	virtual void initPhysics();
+	virtual void renderScene();
+	void resetCamera()
+	{
+		float dist = 41;
+		float pitch = 52;
+		float yaw = 35;
+		float targetPos[3]={0,0.46,0};
+		m_guiHelper->resetCamera(dist,pitch,yaw,targetPos[0],targetPos[1],targetPos[2]);
+	}
+};
+
+void ChainExample::initPhysics()
+{
+	m_guiHelper->setUpAxis(1);
+
+	createEmptyDynamicsWorld();
+	
+	m_guiHelper->createPhysicsDebugDrawer(m_dynamicsWorld);
+
+	if (m_dynamicsWorld->getDebugDrawer())
+		m_dynamicsWorld->getDebugDrawer()->setDebugMode(btIDebugDraw::DBG_DrawWireframe+btIDebugDraw::DBG_DrawContactPoints);
+
+	///create a few basic rigid bodies
+	btBoxShape* groundShape = createBoxShape(btVector3(btScalar(50.),btScalar(50.),btScalar(50.)));
+	m_collisionShapes.push_back(groundShape);
+
+	btTransform groundTransform;
+	groundTransform.setIdentity();
+	groundTransform.setOrigin(btVector3(0,-50,0)); 
+	{
+		btScalar mass(0.);
+		createRigidBody(mass,groundTransform,groundShape, btVector4(0,0,1,1));
+	}
+
+
+	{
+		//create a few dynamic rigidbodies
+		// Re-using the same collision is better for memory usage and performance
+        btBoxShape* colShape = createBoxShape(btVector3(1,1,0.25));
+		 
+		m_collisionShapes.push_back(colShape);
+
+		/// Create Dynamic Objects
+		btTransform startTransform;
+		startTransform.setIdentity();
+
+		btScalar	mass(1.f);
+
+		//rigidbody is dynamic if and only if mass is non zero, otherwise static
+		bool isDynamic = (mass != 0.f);
+
+		btVector3 localInertia(0,0,0);
+		if (isDynamic)
+			colShape->calculateLocalInertia(mass,localInertia);
+		 
+		btAlignedObjectArray<btRigidBody*> boxes;
+		int lastBoxIndex = TOTAL_BOXES-1;
+		for(int i=0;i<TOTAL_BOXES;++i) {
+			startTransform.setOrigin(btVector3(
+									 btScalar(0),
+									 btScalar(5+i*2),
+									 btScalar(0)
+									 )
+									 );
+			boxes.push_back(createRigidBody((i==lastBoxIndex)?0:mass,startTransform,colShape));		 
+		} 
+		 
+		//add N-1 spring constraints
+		for(int i=0;i<TOTAL_BOXES-1;++i) {
+			btRigidBody* b1 = boxes[i];
+			btRigidBody* b2 = boxes[i+1];
+			 
+			btPoint2PointConstraint* leftSpring = new btPoint2PointConstraint(*b1, *b2, btVector3(-0.5,1,0), btVector3(-0.5,-1,0));
+			 
+			m_dynamicsWorld->addConstraint(leftSpring);
+			 
+			btPoint2PointConstraint* rightSpring = new btPoint2PointConstraint(*b1, *b2, btVector3(0.5,1,0), btVector3(0.5,-1,0));
+
+			m_dynamicsWorld->addConstraint(rightSpring);
+		}
+	}
+
+	m_guiHelper->autogenerateGraphicsObjects(m_dynamicsWorld);
+}
+
+
+void ChainExample::renderScene()
+{
+	CommonRigidBodyBase::renderScene();	
+}
+
+
+
+
+
+
+
+CommonExampleInterface*    ET_ChainCreateFunc(CommonExampleOptions& options)
+{
+	return new ChainExample(options.m_guiHelper);
+}
+
+
+