Visual Geometries/Meshes not Sticking to Link

asked 2012-10-30 23:19:33 -0600

Gwen
81 ●3 ●4 ●9

updated 2012-10-31 09:56:23 -0600

Hi Everyone,

I have exported .STL meshes from Solidworks, and am trying to use them to visualize a mobile base. Some transforms are necessary in <model><link><pose> b/c the coordinate system in Solidworks is shifted. Everything is nicely aligned until I set <static>false</static>, and the all of my transforms get un-done! This only happens for the visual meshes. The collision objects that I have set up using simple geometries stay put relative to the correct reference frame of their links, but it's clear that the visual meshes end up back exactly where they would be if <pose> was all zeros. It's a pretty simple model with four links and three joints. Has anyone else had this issue? Is it due to the type of mesh that I'm using?

I'm attaching a screen shot of my static and dynamic models. I'm happy to share some code if you think it would help, but the mesh inclusion is verbatim to the examples (except using .stl and not .dae).

Thanks! Gwen

Screen Shot: Static on Left, Dynamic on Right

UPDATE: I still don't have a good answer as to why the mesh isn't sticking, but I did check that the same thing happens when I use the pioneer2ex's chassis.dae mesh instead of my *.STL mesh. However, I CANNOT recreate the problem in the mobile robot tutorial if I rotate the chassis by 90 degrees about the z-axis.

Screen Shot: Static on Left, Dynamic on Right, Pioneer Mesh w/ my Model

Screen Shot: Static on Left, Dynamic on Right, Pioneer Mesh w/ Tutorial Model

I have also checked that--in my model--if the visual mesh is replace by a simple geometry, the same thing happens: when static is set to false, none of the geometries stick to their respective links. They all just end up back at <pose>0.0 0.0 0.0 0.0 0.0 0.0</pose>. I should add that I'm not getting any warnings or errors in the terminal from Gazebo. With this additional information, has anyone else had a similar problem? Any solutions? Perhaps a pertinent environment variable for Gazebo is not properly set?

Thanks again! Gwen

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answered 2012-10-31 22:30:00 -0600

Gwen
81 ●3 ●4 ●9

I think I have found the problem. It actually (apparently) has nothing to do with the visualization. I certain friction parameter I passed was wrong enough to disrupt the physics engine (specifically, fdir1). I arrived at this conclusion by commenting out the .sdf file section-by-section. My best guess is that I caused something to become singular or nearly singular so all of the poses were reset. I'm now looking for a way to turn on any warnings or errors from the physics engine that might be suppressed.

Is there a way to toggle warnings from the different components of Gazebo?

If anyone else is having a similar problem, I suggest you first double check all the parameters you're passing to the physics engine.