Further improvements in Bullet MuJoCo MJCF import:

[MJCF import] improved humanoid.xml, inverted_pendulum.xml import (automatically add dummy-links to connect multiple joints between bodies)
[MJCF import] fix bug in quaternion conversion (w,x,y,z) -> (x,y,z,w)

examples/Importers/ImportURDFDemo/URDF2Bullet.cpp

@@ -231,6 +231,8 @@ void ConvertURDF2BulletInternal(
 
 
     bool hasParentJoint = u2b.getJointInfo(urdfLinkIndex, parent2joint, linkTransformInWorldSpace, jointAxisInJointSpace, jointType,jointLowerLimit,jointUpperLimit, jointDamping, jointFriction);
+	std::string linkName = u2b.getLinkName(urdfLinkIndex);
+                          
     if (flags & CUF_USE_SDF)
     {
         parent2joint =parentTransformInWorldSpace.inverse()*linkTransformInWorldSpace;
@@ -314,7 +316,11 @@ void ConvertURDF2BulletInternal(
                 bool isFixedBase = (mass==0);//todo: figure out when base is fixed
                 int totalNumJoints = cache.m_totalNumJoints1;
                 cache.m_bulletMultiBody = creation.allocateMultiBody(urdfLinkIndex, totalNumJoints,mass, localInertiaDiagonal, isFixedBase, canSleep);
-
+				if (flags & CUF_USE_MJCF)
+				{
+					cache.m_bulletMultiBody->setBaseWorldTransform(linkTransformInWorldSpace);
+				}
+				
                 cache.registerMultiBody(urdfLinkIndex, cache.m_bulletMultiBody, inertialFrameInWorldSpace, mass, localInertiaDiagonal, compoundShape, localInertialFrame);
             }
 
@@ -443,6 +449,16 @@ void ConvertURDF2BulletInternal(
                 short collisionFilterGroup = isDynamic? short(btBroadphaseProxy::DefaultFilter) : short(btBroadphaseProxy::StaticFilter);
                 short collisionFilterMask = isDynamic? 	short(btBroadphaseProxy::AllFilter) : 	short(btBroadphaseProxy::AllFilter ^ btBroadphaseProxy::StaticFilter);
 
+				int colGroup=0, colMask=0;
+				int flags = u2b.getCollisionGroupAndMask(urdfLinkIndex,colGroup, colMask);
+				if (flags & URDF_HAS_COLLISION_GROUP)
+				{
+					collisionFilterGroup = colGroup;
+				}
+				if (flags & URDF_HAS_COLLISION_MASK)
+				{
+					collisionFilterMask = colMask;
+				}
                 world1->addCollisionObject(col,collisionFilterGroup,collisionFilterMask);
 
                 btVector4 color = selectColor2();//(0.0,0.0,0.5);
@@ -505,7 +521,12 @@ void ConvertURDF2Bullet(
 
 		btTransform localInertialFrameRoot = cache.m_urdfLinkLocalInertialFrames[urdfLinkIndex];
 
-		mb->setBaseWorldTransform(rootTransformInWorldSpace*localInertialFrameRoot);
+		if (flags & CUF_USE_MJCF)
+		{
+		} else
+		{
+			mb->setBaseWorldTransform(rootTransformInWorldSpace*localInertialFrameRoot);
+		}
 		btAlignedObjectArray<btQuaternion> scratch_q;
 		btAlignedObjectArray<btVector3> scratch_m;
 		mb->forwardKinematics(scratch_q,scratch_m);

examples/Importers/ImportURDFDemo/URDFImporterInterface.h

@@ -30,6 +30,7 @@ public:
 	/// optional method to provide the link color. return true if the color is available and copied into colorRGBA, return false otherwise
 	virtual bool getLinkColor(int linkIndex, btVector4& colorRGBA) const { return false;}
 
+	virtual int getCollisionGroupAndMask(int linkIndex, int& colGroup, int& colMask) const { return 0;}
 	///this API will likely change, don't override it!
 	virtual bool getLinkContactInfo(int linkIndex, URDFLinkContactInfo& contactInfo ) const  { return false;}
     

examples/Importers/ImportURDFDemo/URDFJointTypes.h

@@ -55,5 +55,11 @@ struct URDFLinkContactInfo
 	}
 };
 
+enum UrdfCollisionFlags
+{
+	URDF_FORCE_CONCAVE_TRIMESH=1,
+	URDF_HAS_COLLISION_GROUP=2,
+	URDF_HAS_COLLISION_MASK=4,
+};
 
 #endif //URDF_JOINT_TYPES_H

examples/Importers/ImportURDFDemo/UrdfParser.h

@@ -58,6 +58,8 @@ struct UrdfGeometry
 	btVector3 m_boxSize;
 	
 	double m_capsuleRadius;
+	double m_capsuleHalfHeight;
+	int m_hasFromTo;
 	btVector3 m_capsuleFrom;
 	btVector3 m_capsuleTo;
 
@@ -80,10 +82,7 @@ struct UrdfVisual
 	UrdfMaterial m_localMaterial;
 };
 
-enum UrdfCollisionFlags
-{
-	URDF_FORCE_CONCAVE_TRIMESH=1,
-};
+
 
 
 struct UrdfCollision
@@ -92,6 +91,8 @@ struct UrdfCollision
 	UrdfGeometry m_geometry;
 	std::string m_name;
 	int m_flags;
+	int m_collisionGroup;
+	int m_collisionMask;
 	UrdfCollision()
 		:m_flags(0)
 	{