Why we need Maya's set driven keys.
Here is a few reasons why Blender should invest time to develop a set driven keys system that allows avoiding dependency cycles when using drivers, constraints, parenting.
A simple example of having an empty that switches the visbility of FK Controls of a bone chain by moving it on the Y axis.
in Maya it's simple, orient constraints the joints to the controllers, drive the visbility of those controls with the empty's Y location and parent that empty to the first joint(no python expression needed) limit the translation to only Y with certain distance ..........no dependency cycles and as you can see the editor is convenient and easy to use(Driver & Driven).
Now in Blender, two FK chains one for the deform bones and the other for custom shapes , 3 copy rotation constraints for the deform bones to follow the custom shapes..add a driver to each custom shape's hide property, set the appropriate settings and expression.parent the control bone (empty) to the end deform bone, Here you already hit a dependency between constraints & parenting and if you add a limit location constraint to the control bone then another dependency is detected.
It seems that Blender is doing everything in the same hierarchy while Maya in a parallel or something, I have hit tons of dependency cycles in Blender for such simple setups that i couldn't find a way to go around them, hopefully either this system can be looked at and added or maybe when the everything nodes reach the rigging part, then this kind of roadblocks should be used as a good reference for solving them.
4 Comments
It looks like maya is solving movements in local space before applying parent transformation in its dependency graph, whereas blender solves the parent transform first. I can see how this would be nice to have for rigging.
can you provide the .blend? it's not clear exactly what you're doing from the description. it could be user error, or it could be that the dependency graph needs to be smarter/more granular (both maya and blender build a dependency graph regardless of how the features are named or called - cloning maya's UI won't help here)
* @Bassam Kurdali * Sure, here is the Blend file. Blend This is just a simple setup for FK controls visibility using a single control or in Blender's case a bone......the chain is constrained to the controls and the controls are driven by the bone but if you parent the control bone to the end bone(wrist) then the dependencies happen but not in Maya's case.
Yes please!! Beautifully crafted demonstration!