I've been following an online robot modelling tutorial and I'm having an issue where part of my mesh is invisible when the armature modifier is turned on. When the modifier is turned off I can see them again.

I had already started animating my model before I realised two of the cylinders on his legs were missing!

I'm new to blender and i'm totally lost as to what the problem might be, any help would be welcome!

this is how it looks with the armature modifier turned off

This is how it looks with the armature modifier turned on, as you can see the cylinders on his legs have disappeared

  • $\begingroup$ Can you include a .blend file? You can upload it through blend-exchange.giantcowfilms.com $\endgroup$
    – Shady Puck
    May 11, 2016 at 21:33
  • $\begingroup$ Make sure they're weighted properly :-/ $\endgroup$
    – Matt
    May 11, 2016 at 21:59
  • $\begingroup$ I've added a .blend file now $\endgroup$ May 12, 2016 at 9:30

2 Answers 2


You get a twist problem on your "Track To" constraint on KneeCylinder.L / KneeCylinder.R.

(Try set influence of this constraint, and you will see your cylinder).

Quick fix by Rolling your bone by 180° (edit mode, and set roll to current roll + 180°)

  • $\begingroup$ Thanks for the response! I can see how to roll the bone 180°, but how do I set roll to current roll + 180°? $\endgroup$ May 12, 2016 at 11:04
  • $\begingroup$ Several ways : * on edit mode, Ctrl+R, and 180. This will add 180 to your current roll. * Or Click on your roll, this will display (for example) 2.5d. Then add +180 to display 2.5d+180, and press Enter. This will add 180° to your current 2.5° $\endgroup$
    – Julien
    May 12, 2016 at 12:36
  • $\begingroup$ Great! Thank you. Okay, one more silly question. I moved the KneeCylinder.L and KneeCyliner.R bones to a different bone layer and now I can't figure out how to find/select them in order to change their roll. $\endgroup$ May 12, 2016 at 12:52
  • $\begingroup$ You can choose what bone layers you want to display on armature properties, panel skeleton $\endgroup$
    – Julien
    May 12, 2016 at 15:32
  • $\begingroup$ You're welcome. Don't hesite to set my answer "usefull" if this answer your question (as it seems to be) $\endgroup$
    – Julien
    May 13, 2016 at 8:31

Problem solved! Turns out the vertex group weights on the mesh were incorrect. The mesh for the knee cylinders was also weighted to the "upper_arm.L", "upper_arm.R", and "rubber_material" vertex groups.

Once I removed the incorrect weighting the cylinders re-appeared.


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