# Posts tagged ‘Pivots’

Heres a list of what I’ve found should be in a rig. It’s from studying generalized rigs and demos, Building them, and most of all asking the animators I work with every day.

• Main torso control with keyable pivot
• Independant pelvis control
• Independant chest control
• Head control with keyable rotation space (local/world) and keyable pivot.
• FK/IK  arms with keyable rotation space (local/world) in FK mode.
• FK/IK legs with keyable rotation space (local/world) in FK mode and keyable foot pivot in IK mode – additional support for quick pivot places (gui based).

On top of this, you could add stretching, breakable limbs, pinnable arms legs etc – but this is the bare bones rig.

Edit: The keyable head space pivot is an idea inspired by  Jason Schleifer’s, Animator friendly rigging. Go check out his site here. And Bernard’s utterly stunning softimage reel over here. – sorry if there was any confusing, if people thought it was my idea.

An animatable pivot is essentially a transformed objects space about which the object rotates and moves in. This transform space can have two purposes and two relatively different affects: either your object rotates/moves about an arbitary ‘pivot’ or this ‘pivot’ transforms your object -They sound the same but are different in the results they acheive.

With the first system you take into account the actual objects transform to acheive its new transform; your only keying the actual object. With the second your transforming the target ‘pivot’ object essentially pinning your object about it. Why do you need a system to handle both?

Well,  in local relativity (in terms of a heirachy or closed system) the first system is key in transforming controls about a character: the ankle about the toe for instance or the chest about the hip for bending down. The second system is in world relativity, by transforming an object about the transform of another we can essentially make it a fake parent – glue it to a surface for example.

A good example of both systems in action is a skateboard move, the foot needs to be glue to the board (transforming space) but may itself need to transform about something, the edge of the board for example. Ontop of this the board itself may need to transform about the hands, to be grabbed for example.

This is why a system like this exists as another layer over the base rig, much like a pose tool is. Key generation should only be on the necessary controls and not on extraneous sliders (even if your using sliders to key them)  etc unless there part of the base rig. When working in transform spaces is vitual that keys  get put onto the actual objects.

So as I was mentioning on CGTalk, the rule I think to animating in transform spaces is that you dont generate automated keys. Or force keys to be generated in realtime – as basically you’d be generating keys for the target object everytime you moved pretty much  anything else. So I think i’ll build a set of tools, animators can constrain and transform controls in any space when they want. The benefit of this is that there generating the keys, id have to build either functionality to work with the f-curve or maybe a ‘pseudo’ f-curve transform space when there using it.. else its just gunna be a transform type-in. As to this system it would work above the rig as a whole, that makes a lot more sence – basically our bodies/skeleton is setup and then ontop of this world interaction happens; we lean on things, rest etc etc.. transforms that happen ontop of how were built.

Anyway so i think ive locked down my rig, amazingly – (probably havent though) but the generality is there:

1. Torso Control – controls upper body
2. Hip Control – independant .Custom built (from the ground up) spline IK system, using either deboor, cardinal, Nurbs  bspline or piecewise curves. Control of length, stretching compression, dynamic realtime if needed, automatic twist and bias control to fix pops.
3. Chest Control – independant, drives head positionally
4. Head Control – independant, drives neck when translated
5. Clavicals – independant, drive arms positionally only
6. Arms – IK/FK, independant orientationally. Ik with pole vectors.
7. Hands, fk digits control, digit curling at second joint. Simple pose storing
8. Legs – ik/fk pole vectors
9. Feet – ankle, ball of foot and toe control
10. transform space toolbox, ability to transform any control about any other control/object on the fly per shot. Possible custom controls built – but always making ‘real’ keys on actual controls.
11. Twist on arms, control for bias position at shoulder and wrist. Additional skin tweeners at shoulder/elbow/wrist driven by positional space targets.

They can be achieved, but currently its underwraps.
Clip 1 Clip 2