Moving frames in 3D (6dof)

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Hi everybody, I have a question about frames , transforms and TF. I would like to extend the simples Turtle tf tutorials ( http://www.ros.org/wiki/tf/Tutorials ) based on a 2D space but I'm having a lot of troubles doing it. Unfortunately I didn't find (yet) something on the mailing list or on ros-answers... I have this 3 frames:

• world_frame
• odom_frame (with a fixedtransform respect to world)
• cart_frame (I move this frame with the odometry data)

Here is the code:

static tf::TransformBroadcaster br;
static tf::TransformListener tf_;

and this

while (ros::ok()){

transform.setOrigin(tf::Vector3(3,3,0));
transform.setRotation(tf::createQuaternionFromRPY(0.0,0.0,0.0));
br.sendTransform(tf::StampedTransform(transform, ros::Time::now(), "/world", "/odom"));

here, with updateOdom I calculate the x,y,theta position from the odometry (like the tutorial)

updateOdom(1);
try
{
    transform.setOrigin(tf::Vector3(x,y,0));
    transform.setRotation(tf::createQuaternionFromRPY(0.0,0.0,th));
    br.sendTransform(tf::StampedTransform(transform, ros::Time::now(), "/odom", "/cart_frame"));
}  catch(tf::TransformException e)
{   ROS_WARN("errore transformpose (%s)", e.what()); }

Now what I'm trying to do is move the cart_frame not only with the x+y+th params but with a full 6-dof transform, as if the the cart_frame was moving on a circular garage car ramp, and here starts my question: the simplest way is to add the information to the odometry, so I can call the sendtransform() directly, but what if I had a situation where the odometer always sends only 2D transforms? In the example I tried to send a transform with a small pitch at the beginning of the while (ros ok())

transform.setOrigin(tf::Vector3(3,3,0));
transform.setRotation(tf::createQuaternionFromRPY(0.0,0.4,0.0));
br.sendTransform(tf::StampedTransform(transform, ros::Time::now(), "/world", "/odom"));

and this is the outcome http://www.youtube.com/watch?v=d4ktwwukCV0, not properly what I want...

Ok, probably I am very tired and confused today but if someone can tell me where I'm wrong I'll be infinitely grateful =) Thank you

Augusto