[ros-users] Weirdness in URDF tutorials

[Björn Giesler]

Hi,

I'm trying to create a URDF model for my robot, which happens to be an R2-D2 replica so I was thrilled to find the wiki contains a series of tutorials that create a R2-D2 URDF. I'm trying to follow the tutorial on my robot's computer, a Zotac Zbox (NVIDIA ION-based) which I'm connecting to via VNC.

Is it possible that those tutorials are outdated and the URDF syntax and semantics have changed? It seems that transforms and materials don't behave the way they should.

This is how the second tutorial step should look like according to the wiki:

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and this is how it looks on my machine:

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Notice that the cylinder is OK, but the second shape (a .6x.2x.1 box) is rotated and also white. The URDF file I used is unmodified from urdf_tutorial, and its text is exactly as posted in the wiki.

The first thing I noticed was that the coordinate assignment looks off causing the box to be higher than wide instead of vice versa. So I tried to just put a couple of colored boxes in the x, y, and z directions to see what the proper assignment was. I got as far as one box, the URDF file is this:

<?xml version="1.0"?>
<robot name="R2-D2">
  <link name="base_link">
    <visual>
      <geometry>
	<cylinder length="0.6" radius="0.2"/>
      </geometry>
      <material name="white"><color rgba="1 1 1 1"/></material>
    </visual>
  </link>

  <link name="redbox">
    <visual>
      <geometry>
	<box size=".1 .1 .1"/>
      </geometry>
      <origin xyz="1 0 0"/>
      <material name="red">
	<color rgba="255 0 0 0.5"/>
      </material>
    </visual>
  </link>

  <joint name="base_to_redbox" type="fixed">
    <parent link="base_link"/>
    <child link="redbox"/>
  </joint>
</robot>

...so it's a red box at xyz="1 0 0". This is how it looks like:

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So the box is there, but it's not red... 

Can anyone tell me what's going on here?

Thanks a lot in advance,
Bj?rn
-- 
Bj?rn Giesler
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