How do I modify a COLLADA model?

asked 2012-05-22 08:21:18 -0600

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updated 2014-01-28 17:12:25 -0600

ngrennan
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Hi, I'm modeling a robot and using the meshes that are available at nxt_description. But I noticed that 3707.dae mesh is not centered (?) and I was wondering how could I modify it (and maybe push it to the repository).

Also, how should I make new meshes that use the same scale than those who are already made? And how do I get the textures from the .dat files of LDraw?

I'm sorry if this is already answered or documented somewhere, but the only thing I could find was this post and it didn't help me much :(

Thanks in advance,
Miguel.

Update:

I managed to get the COLLADA models, but some of them are inside out and don't show correctly on Gazebo or rviz. For example, look at this tire:

image description

As you can see, the inside of the tire is shown instead of the outside. Any ideas on how to solve this?

Thanks! :)

answered 2012-05-25 02:24:26 -0600

Stefan Kohlbrecher

24361 ●173 ●299 ●444 https://www.energy-rob...

Normally, meshes should use meters as their length unit (as specified in REP103). It is then straightforward to just model the part and to use it for a URDF model (or in gazebo) without having to care about scaling. If your other meshes are not given in a meter scale, you have to get the scale factor from somewhere.

You should be able to import your .dae mesh to most 3D modeling programs and edit it, but unfortunately there is a quite high likelihood that something goes awry during import (at least when using textures and similar 'advanced' stuff). For example, importing your .dae example mesh didn't work with blender 2.63 for me. It can be opened using Meshlab however. Converting it to .3ds using Meshlab and then importing to Blender worked (but the geometry is very large, so I assume the nxt parts do not use meters as their length unit, or something went wrong during the conversion process).

If you want to look into modeling COLLADA using Blender, this post documents some of my experience with that. :)

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Thanks Stefan, I'll try using Blender... As for the large geometry, I don't know why but NXT parts use a really big scale. You have to use a scale parameter of 0.0004 (!!) in the urdf files in order to get the right sizes.

Capelare ( 2012-05-25 06:54:54 -0600 )edit

With regards to your edit question and the "inside out" parts: This most likely is a problem with face normals. Make sure they have consistent direction (pointing outside the model). You can do that in Blender in Edit mode by pressing Ctrl+N.

Stefan Kohlbrecher ( 2012-06-06 08:10:24 -0600 )edit

Thanks again, Stefan! I tried that, but then I export to .3ds and when I import the file in Meshlab it says "No vertex field found." I'm trying to find a solution somewhere right now ;-)

Capelare ( 2012-06-06 08:25:20 -0600 )edit

Thanks again, Stefan! I tried that, but then I export to .3ds and when I import the file in Meshlab it says "No vertex field found." I'm trying to find a solution somewhere right now ;-)

Capelare ( 2012-06-06 08:25:23 -0600 )edit

I solved it by exporting to .obj (with "Keep Vertex Order" activated). But now my .dae model is all white -.-

Capelare ( 2012-06-06 08:37:06 -0600 )edit

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