complex urdf files
How do most people end up creating their complex urdf and sdf files? Most of the tutorials I see edit the xml in their text editor of choice.
add a comment
The "segment" template would need to be parameterized such that you can specify where to attach the hing, and how long the segment is, etc. Then you can create a new "Arm" template that pulls in multiple "segment" templates to build up a arm with several segments.
like how xacro does this, you mean ? ;)
As an example of using empy, see the way (the) O(S)R(F) created the worlds and parts for the ARIAC challenge: osrf/ariac/src/osrf_gear/worlds/gear.world.template. It's just one example, but does illustrate the idea.
Correct. I've used Jinja2 in the past to create urdfs where each sensor type (gps, imu, camera, etc) was it's own template. When I needed to test a new sensor configuration, I could just include that template, and pass it the correct parameters of where to mount the sensor, frequency to publish data, topic to publish on, noise parameters, etc. It worked quite well.
Which again is exactly how it works with xacro :)
Not saying using something else cannot be beneficial, just making sure it's clear that that is not much different from how xacro works. See ubi-agni/human_hand/model/human_hand.urdf.xacro for an example.
1
I'm surprised that everyone seems to prefer defining their models in code
you have a sample size of 2 here (at least here on ROS Answers).
And this is coming from a community that consists of a lot of programmers.
rather than using some CAD tool that exports the model to the format of choice.
that would be nice, but:
- most of those tools cost a lot of money
- it's way quicker to add an additional link by copy-pasting some text and adjusting some parameters than to fire up your cad tool (probably Windows only), loading the assembly, rearrange geometry, run an exporter and then fixing up / post processing whatever the exporter didn't do correctly
- anyone can edit text files, becoming proficient with a CAD tool is not as easy
- CAD tools typically don't use open formats, increasing vendor lock-in
- CAD tools don't necessarily support ...
..
I'm not dismissing using more high-level modeling tools for this (and in fact, they are being used, see fi sw_urdf_exporter and dfki-ric/phobos), it's just that in an environment that is so code heavy/centric, being able to generate models from parametric descriptions fits the overall development workflow a bit better.
All in my opinion of course.
