Driver : delta Z between two bones?


I want to drive a bone X rotation with a value based on two other bones Z position

TargetBone.rotation.x = BoneA.location.Z - BoneB.location.Z

but I dont understand how to do that with dirvers
it is asking for a path, but how do I find the path ?
do I have to use a property ? then how do I update that property from that delta Z ?

thanks for your help

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The easiest way to find a path, for me, is to right click in a particular field and copy as new driver, then paste as new driver somewhere else. Once you have a field, you can copy/paste that entire variable with the copy/paste buttons in the driver editor, or you can just select and copy the data path text.

There’s also “copy data field” operation, but there are problems involved with it.

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In var_001 click the DNA like icon next to the name, and change it to the one that like this : (x)
Then you’ll have the same settings as the first variable ( var)

then the expression could be something like : abs(var - var_001)

Or you can retrieve the path as bandages suggests ,
using path is a more universal way of accessing any data, but as you’re dealing only with location,
the (x) icon type is enough.

I just figured out that in the menu there is a “Distance” variable type worth looking into for your case. An now you’ve got 3 different ways of doing what you want, isn’t that wonderful ?

Good luck !

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thanks but it does seem to take my input

ok I found out I had to use transform channel

whish these “drivers” feature was more documented with examples and stuff