added LICENSE.txt and AUTHORS.txt file

add MultiBody Custom Creation example, to show how to import data from a URDF file and fill up your own data structures.
add btMultiBody::setBaseWorldTransform method
todo: fix cmake build, this patch is premake only

examples/MultiBody/MultiBodyCustomURDFDemo.cpp

@@ -1,3 +1,15 @@
+/* Copyright (C) 2015 Google
+
+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 "MultiBodyCustomURDFDemo.h"
 
@@ -6,6 +18,9 @@
 #include "../CommonInterfaces/CommonMultiBodyBase.h"
 
 #include "../Importers/ImportURDFDemo/URDF2Bullet.h"
+#include "../Importers/ImportURDFDemo/MyURDFImporter.h"
+#include "../Importers/ImportURDFDemo/MyMultiBodyCreator.h"
+
 #include "CustomMultiBodyCreationCallback.h"
 
 
@@ -34,31 +49,100 @@ MultiBodyCustomURDFDemo::~MultiBodyCustomURDFDemo()
 
 }
 
+
+static void myPrintTree(const URDFImporterInterface& u2b, int linkIndex, int indentationLevel)
+{
+    btAlignedObjectArray<int> childIndices;
+    u2b.getLinkChildIndices(linkIndex,childIndices);
+    
+    int numChildren = childIndices.size();
+    
+    indentationLevel+=2;
+    int count = 0;
+    for (int i=0;i<numChildren;i++)
+    {
+        int childLinkIndex = childIndices[i];
+        std::string name = u2b.getLinkName(childLinkIndex);
+        for(int j=0;j<indentationLevel;j++) printf("  "); //indent
+        printf("child(%d).name=%s with childIndex=%d\n",(count++)+1, name.c_str(),childLinkIndex);
+        // first grandchild
+        printTree(u2b,childLinkIndex,indentationLevel);
+    }
+}
+
+
+
+
+class TestMultiBodyCreationCallback : public CustomMultiBodyCreationCallback
+{
+	virtual int allocateMultiBodyBase(int urdfLinkIndex, int totalNumJoints,ScalarType baseMass, const Vector3dType& localInertiaDiagonal, bool isFixedBase)
+	{
+		printf("added base\n");
+	}
+
+    virtual void addLinkAndJoint(int jointType, int linkIndex,            // 0 to num_links-1
+                       int parentIndex,
+                       double mass,
+                       const Vector3dType&	inertia,
+                       const QuaternionType &rotParentFrameToLinkFrame,  // rotate points in parent frame to this frame, when q = 0
+                       const Vector3dType&	jointAxisInLinkFrame,    // in Link frame
+                       const Vector3dType&	parentComToThisJointOffset,    // vector from parent COM to joint frame, in Parent frame
+                       const Vector3dType&	thisJointToThisComOffset)       // vector from joint frame to my COM, in Link frame);
+	{
+		printf("added link\n");
+	}
+                 
+};
+
 void MultiBodyCustomURDFDemo::initPhysics()
 {
     int upAxis = 2;
     m_guiHelper->setUpAxis(upAxis);
 	createEmptyDynamicsWorld();
+	btVector3 grav(0,0,0);
+	//grav[upAxis] = -10.f;
+
+	m_dynamicsWorld->setGravity(grav);
+
     m_guiHelper->createPhysicsDebugDrawer(m_dynamicsWorld);
-    m_dynamicsWorld->getDebugDrawer()->setDebugMode(
-        //btIDebugDraw::DBG_DrawConstraints
-        +btIDebugDraw::DBG_DrawWireframe
-        +btIDebugDraw::DBG_DrawContactPoints
-        +btIDebugDraw::DBG_DrawAabb
-        );//+btIDebugDraw::DBG_DrawConstraintLimits);
 
 
-    
+	
+    MyURDFImporter u2b(m_guiHelper);
+	bool loadOk =  u2b.loadURDF("r2d2.urdf");
+
+	if (loadOk)
+	{
+		u2b.printTree();
+		int urdfRootLinkIndex = u2b.getRootLinkIndex();
+		myPrintTree(u2b,urdfRootLinkIndex,0);
+
+		btTransform identityTrans;
+		identityTrans.setIdentity();
+	
+		btMultiBody* mb = 0;
+        
+
+		//todo: move these internal API called inside the 'ConvertURDF2Bullet' call, hidden from the user
+		int rootLinkIndex = u2b.getRootLinkIndex();
+		printf("urdf root link index = %d\n",rootLinkIndex);
+		MyMultiBodyCreator creation(m_guiHelper);
+
+		bool useMultiBody = true;
+
+		ConvertURDF2Bullet(u2b,creation, identityTrans,m_dynamicsWorld,useMultiBody,u2b.getPathPrefix());
+		mb = creation.getBulletMultiBody();
+
+	}
 }
 
 void MultiBodyCustomURDFDemo::stepSimulation(float deltaTime)
 {
-   
     m_dynamicsWorld->stepSimulation(deltaTime);
 }
 
 
-class ExampleInterface*    MultiBodyCustomURDFDofCreateFunc(struct PhysicsInterface* pint, struct GUIHelperInterface* helper, int option)
+class ExampleInterface*    MultiBodyCustomURDFDemoCreateFunc(struct PhysicsInterface* pint, struct GUIHelperInterface* helper, int option)
 {
 	return new MultiBodyCustomURDFDemo(helper);
 }