I downloaded a 3d model of a car. By judging by the skins and images available model treats wheels and car body as separate nodes. I want to access its child nodes (wheels) to specify animation.

But I don't know the names of its child nodes. Is it possible to figure out names of its child nodes by looking at the file content. I have a obj file of the 3D model. I am using JMonkey 2.

here is the link thefree3dmodels.

Thank you in advance

  • 1
    \$\begingroup\$ For the record, .obj is a pretty common file extension, you should first of all find out which of the different formats you are dealing with. \$\endgroup\$ Jun 16, 2011 at 9:59
  • \$\begingroup\$ It is a Wavefront file, the groups of this file have numerical names 000 through 037. \$\endgroup\$ Jun 16, 2011 at 13:23
  • \$\begingroup\$ @eBusiness Can you tell me how to access them.(I prefer JMonkey). That model is a Trimesh. Is there a way to identify which number refers which mesh. In this case group id of a wheel? \$\endgroup\$
    – Niroshan
    Jun 16, 2011 at 15:07
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    \$\begingroup\$ I can't tell, and I don't know JMonkey. Though I'm not certain that there is an easy way of doing what you want, it's only the triangles that are grouped, not the vertices, and you'd animate a model by moving the vertices. But then again, I'm not an expert 3D programmer, I can't say for sure that there isn't some trick. \$\endgroup\$ Jun 16, 2011 at 16:18

1 Answer 1


According to the obj file specification it should be a string after the 'g' command, but from my experiences each obj exporter handles those things specifically.

It might help to add link to obj file in your first post.


According to the model file, those wheels are groups with numbers 13, 14, 24, 25 Proof:


So those faces (and according vertexes, normals and textures) after line g part 013 to the next line with g command is the mesh of the wheel and so on..

I'm not using JMonkey so I don't precisely know how to rotate those parts, but you could cut the car mesh into two files (wheels and rest) and then it should be easy to animate..

  • \$\begingroup\$ I added the link. how can I access the groups to apply some texture or to animate them? \$\endgroup\$
    – Niroshan
    Jun 16, 2011 at 15:17

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