Chapter 6: Gimbal Lock

This is the sixth chapter of How To Cheat in Maya 2012. This chapter will talk about a common problem quite a few animators run into, Gimbal Lock.

Before I go into it from the notes I got from the chapter on ways how to avoid it, I will give a brief outline of what it is Gimbal Lock happens in anything that can rotate on all three axis - this happens in all 3D software. It's the result of mathematical calculations when using Euler (pronounced as "oiler") interpolations.

Maya has other rotation solutions available that won't Gimbal Lock (called Quaternion) - but works different and therefore the Graph Editor no longer makes visual sense of what is on screen, so Euler rotations are used if we want to use splines in any capacity whatsoever.

For the rotation within the axis to be mathematically possible with a manipulator, there must be a hierarchical order to them. 

Anything can rotate in X, Y and Z within Maya has rotation. The axis can be set in any combination of the three axes - the last axis is the top of the hierarchy:

ROTATION ORDER: XYZ
Hierarchy starts with the last axis

• X is the child of Y, Y is the child of Z. The last axis will always rotate the other two wih it as if they were in one piece:

          Z AXIS AFFECTS X AND Y

• Rotating the Middle axis brings the first axis with it as if they were a single piece
  
  Y AFFECTS X
  
• Rotation the first will only affect that one

          X AXIS HAS NO CONTROL OVER OVER AXIS

If the rotation was any different (I.E. Rotation order: ZYX) the principles would be the same.

Rotation Modes

Three rotation modes: 

Gimbal: shows how the rotations happening, it's technically consider the only "real" mode.

Local: this mode rotates all three of the axis together so it appears that your rotations are always lined up. This is the default and it's useful once you understand what's going on.

World: keeps the axis oriented to the world space. It's not really used for animating unless there's's no east way to get what you need.

It's good switching between the three modes as it helps with your work flow as long as you remember what you mode does what.

Setting Rotation Order

The best way to combat Gimbal Lock is to set the rotation orders of any three axis controlled. Figuring out the rotation order depends on what you need to do in your animation. When analyzing the movement you're going to animate, looking at the movement to figure out what axis is rotated the furthest, the axis that is the least and the base you choose off of that is a good idea.

Zeroing Out Poses

The best way to guarantee that gimbal lock has a minimal chance to happen is zeroing out your poses when blocking. When the rotations keep picking up from the previous ones when posing, the values accumulate inefficiently over time. When you zero out poses, you start a new poses by setting the three-axis controllers back to zero, by doing this you make sure you are not up stacking up the rotations on top of each other, and it also means Maya can interpolate between keys much more efficiently.

This sums it up for my posts on How To Cheat in Maya 2012, very good book that gave me a lot of tips to consider, I was originally a bit put down by the fact it wasn't for the 2014 version of Maya but as I researched and said in an earlier post - there really isn't much difference in each iteration of the software. it is most definitely a book I will use again in future.