[Bf-committers] Drivers Delayed (Dependency Issue)

Tobias Oelgarte tobias.oelgarte at googlemail.com
Sun Feb 20 09:39:24 CET 2011

I made some tests with the drivers and found out that they are delayed. 
Actually they get evaluated first. Before the objects they are depending 
on are getting updated. Even if there is no cyclic dependency they will 
be first, getting the input of the previous frame, making them lag one 
frame behind the changes.

I posted a bugreport yesterday, but the tracker seams to be down 
currently. Since i think, that this is a serious issue, i posted it also 
on this mailing list.

I uploaded a very simple example to http://www.pasteall.org/blend/5309
It contains a tiny armature consisting of one parent bone "base", 
followed by a chain of the bones consisting of "rot1" and "rot2". "rot2" 
is animated and will be used as the input for bone "driven", that is a 
child of "base". Last steps ensures that "rot1"/"rot2" are not depending 
on "driven". "driven" has a single driver that updates the location of 
the bone, depending on the rotational difference between "rot1" and "rot2".

Ideally "rot2" would be changed by the animation first, then "driven" 
would evaluated. But instead the driver is evaluated first, ignoring the 

Greetings from
Tobias Oelgarte

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