# Could someone please explain gimbal lock?

I have read the Wikipedia page on gimbal lock, and am still confused about the entire matter. My understanding is that, using a local coordinate system, if you rotate a model about its X axis then its Y and Z axes experience gimbal lock, and become "locked" together. However, my understanding is that if you rotate the X axis, then both the Y and Z axes rotate with it, and as such remain separate. Wikipedia, as always, while a good resource is difficult to understand on this topic. Could someone please endeavor to explain this to a person who does not have a Master's in physics or mathematics?

I gather that it's an inherent weakness of just storing three axial rotations (Quaternion, on the other hand, also evaluates orientation value).

(Per ideasman42's comment): We can easily see this for any object using Euler rotational system, by manipulating the rotation widget with transformation orientation set to Gimbal. It turns out to be easy to reproduce, by manipulating 2nd axis in the evaluation order (Z for XZY, or X for ZXY, etc.). I get the following condition on XYZ order by just manipulating Y axis:

Here's an article and a video for alternative explanations of the condition.

• Suggest trying the Gimble manipulator Orientation Mode and enable Rotate, then you can see the problem that happens when 2 axis line up. May 30 '13 at 12:43
• @ideasman42: That's a good demonstration tool. I think what's not readily apparent is why those axis can line up. One tends to picture Euler rotational axis as one rigid body with three perpendicular lines, rotating in unison, while the implementation is not that simple.
May 30 '13 at 13:05
• Gimbal lock does not arise because the axes are calculated sequentially. It has been proven that any rotation representation with three numbers will have a lock or singularity somewhere. You seem to imply that in the 3rd sentence too but it contradicts the 2nd? May 31 '13 at 10:41
• I don't have a good simple explanation, and it's not really wrong to state that gimbal lock specifically happens because the axes are evaluated sequentially. The way it is contrasted with evaluating the axes all at once just seems a bit misleading, doing that would come with its own unintuitiveness and locks. Rotations are just inherently difficult. May 31 '13 at 12:02
• I'll just erase the problematic sentence, then. Thanks, Brecht :)