> Also, I noticed that, at least for the PR2 simulator, the PR2's tf tree is very shallow with base_footprint being the parent frame to a large number of frames. I would have thought that tf tree would closely mimic the physical degree of freedom heirarchy in the PR2 (i.e. base->torso->upper_arm->lower_arm, etc.) Is there a reason for the PR2s shallow tf tree?

The shallow tree allows you to compute the pose between any two links
of the pr2, by chaining only two transforms.  If the tf tree would
mimic the physical degree of freedom heirarchy in the pr2, you'd often
have to chain 10+ transforms to get the pose between two links. So
this is a performance optimization.

Wim


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Wim Meeussen
Willow Garage Inc.
<http://www.willowgarage.com)