One shape key, multiple bones driving it?

Posted this on Stack Exchange, but I thought I’d post here also.

I have a character that has 1 shape key that controls the shape of her thighs (both left and right). What I’d like to do is control this shape key with a driver when either the left or right foot is positioned. In other words, when I move the left foot (IK), the “thighs” shape key is activated. When I move the right foot, the same key is activated. Two bones that activate the same shape key driver. Is this possible?

Yes you can do that. In a nutshell

  1. add a driver to the shapekey
  2. in graph editor switch to drives and select the driver, use ‘scripted expression’
  3. it creates variables named var, var_001… so select bone1 for the first,then ‘add var’ button choose bone2
  4. in the expression you need a line of code like: var/5.00 + var_001/5.00 where 5.0 is the distance that bone moves before key is fully activated

You are a genius! Thank you so much.

For future reference, here are my settings in the driver tab:

Glad it worked. I should have included parentheses in the expression to avoid order of operations problems, something like: (var / 2.5) + (var_001 / 2.5)

Thanks… I’ll put those in. I’m terrible at figuring out expressions.