I made a simple model (wanted to mess with physics and python scripting). Boxy robot

That's bunch of boxes held together with RigidiBody joint (6dof joints with all limits checked)

Problem - model falls apart in play mode:

Broken model

It DOES try to adhere to constraints, but after wobbling for a several seconds it eventually collapses, which is really disappointing.

Here's the file.

Is there a way to fix that (so it adheres to constraints PROPERLY) or should I try another software?

The idea was to try to make this thing walk using physical forces (exercise/fun, not a serious project)

The scene was tested on windows platform, 64bit blender 2.74 on 64bit windows 7.

  • $\begingroup$ it doesn't collapse for me , or I'm missing something ? $\endgroup$
    – Chebhou
    Commented Jul 12, 2015 at 16:22
  • $\begingroup$ @Chebhou: Which platform, which operating system and which blender version (version number, 64/32 bit?). Also, are you absolutely sure that you're starting game engine ("P" key) and not trying to record animation? $\endgroup$
    – SigTerm
    Commented Jul 12, 2015 at 23:46
  • $\begingroup$ @sigTerrm Windows 7 32bit Blender 2.73 and I'm sure I'm starting the game engine : ) $\endgroup$
    – Chebhou
    Commented Jul 12, 2015 at 23:55
  • $\begingroup$ OK , I have tested it on Blender 2.74.5 and yes it's not stable at all as you said $\endgroup$
    – Chebhou
    Commented Jul 12, 2015 at 23:58
  • $\begingroup$ @Chebhou: So it is a possible regression in 2.74, then? That's good news (because at least now I know how to fix that). I'll try 2.73 and 2.75 $\endgroup$
    – SigTerm
    Commented Jul 13, 2015 at 0:15

1 Answer 1


Due to lack of solution I gave up on trying this experiment in blender.

I also investigated V-Rep as possible alternative only to find out that it has same issue.

In the end it looks like I'll have to do that experiment (when I have time) in unity3d, because PhysX apparently does not have this stability problem.


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