laser_assembler and laser.bag issue

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Then what about http://wiki.ros.org/laser_assembler and http://answers.ros.org/question/10102/laser-assembler-with-hokuyo-utm-30lx/?answer=14794#post-id-14794 ? Laser_assembler gets laserscans, transforms them according tf topic and save them as you mention. What is the utility otherwise?

Checking the code I guess you are right :S But the documentation is confusing! Do I need to transform all the scans of the laser before using the laser_assembler? What is the best way to do this? Isn't there any node that takes scans and tf and convert to 3D? Because that would be very useful :)

You don't need to send laser scans transformed in a fixed, but you need to provide the information to be able to transform them to tf. Scans + tf -> 3D = laser_assembler.

There is something I'm not understanding at all. If I publish scans and also tf, laser_assembler will transform the laser scans, yes or no? If yes, how to specify with tf? Since, as I say, tf is a tree of frames and transformations (but this is another question). What does laser.bag contains?

You specify a fixed_frame to the laser_assembler. The scans itself have their frame in the message. Laser_assembler will transform the scans to this fixed_frame.

"scans itself have their frame in the message" that is in the laser.bag, but it is always like that? If I fix a Hokuyo to a motor, and publish scan messages, how do I specify those frames from the motor angle?

You/or someone must send the tf message. The laser's frame is a parameter of the laser driver.

I really thank you for your help, but there is something that I am missing. I will try to go deeper and ask more detailed questions.