3ds MAX Cat rig, why ankle bone so unresponsive to pelvis motion?

#1

Ok coming back to Max after a while- CAT is new to me

 I got a bird rig from editing an allosaur preset but if you check this video,

[vimeo]52965864[/vimeo]

 [http://youtu.be/wEiZQ3u9nj4](http://youtu.be/wEiZQ3u9nj4)
 
  the screen closest red joint demonstrates what i feel is a problem regrds CAT- sometimes the ankle seems stuck to its location when the pelvis is moved or rotated around, what I would like is a more procedural result where as the thigh raises the whole leg chain stretches up, and similarly forward if being pulled forward etc etc
 
 I can get a better result by doin my own reverse footlock in max's own bones system, any help appreciated,
#2

That is how the CAT limb works. The “Ankle” in this case is just like the foot in a human rig, and it is not expected to rotate as the pelvis is adjusted.

You can try making a 3-bone limb instead and see if that gets you decent results. That way the limb’s IK solver will affect that ankle joint. I’m personally not a huge fan of CAT’s IK solving for bone chains greater than 2, but it may work fine for you.

You can also dig into setting up a reverse foot rig with CAT. You’ll want to turn off CAT’s default static matrix and use Animation Controller on the Setup Layer. That will give you a lot of freedom to wire or script controllers to drive the ankle rotation. A custom setup like that will preclude you from using CAT Motion layers, but if that’s not an issue for you, it should give you a lot more flexibility.

#3

Helpful response- 'groo!

I actually rigged up a reverse foot lock in regular max bones and linked that to the pelvis- works ok actually AND pipes thru our game engine- phew

But I would be very interested to know more about doing it ALL in CAT,

trying to find more ‘under the hood’ tutorials using CAT is extremely hard

This sentence is what I need to get to grips with

"turn off CAT’s default static matrix and use Animation Controller on the Setup Layer. "
How would I go about that? I would like to dig deeper with CAT, for the reason that 3 bone ik chains might be needed in future…

If you can scribble a coupla notes on that that would be mega-super-awesome!!!

#4

On the Hierarchy Panel->Link Info you’ll find a bunch of options for CAT bones, including radio buttons for Static Matrix or Animation Controller.

Enabling Animation Controller will give you access to PRS parameters in Setup mode for wiring, etc.

You’ll want to enable the Additive To Setup Pose checkbox (also under Link Info) so that any wiring you do won’t be overridden by an Animation Layer.

E.g. with this method you could apply a Noise Float to one of your position tracks in Setup Mode and then all your animations would be additive to that. (Not that you would ever do that, but it gives you an idea of what can be done.) CAT’s Apply Max IK macroscript takes advantage of this functionality to apply Orientation Constraints in setup mode that can be enabled or disabled using a slider (although in Max 2013, there appears to be a bug with it).

Good luck with it. Hope this helps.

#5

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