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dude5487
04-03-2007, 07:07 PM
I am getting ready to rig a couple of quadraped characters and was wanting to start a thread on the theory of the subject. I know that the new issue of 3D World has a lot of great information this issue which I am particularly excited about.

I was wondering if anyone could post their thoughts on theory as well as there experience with various types of quadraped rigs they have made, ie a dino quad or a domestic house cat. As well as any tutorials, online or on video training materials.

I hope we can get some awesome discussion going! I look forward to all responses!

Thanks!

BoostAbuse
04-04-2007, 09:33 PM
general rule of thumb for me is:


joint placement - this is numero uno when working with quads as there needs to be more support in areas you wouldn't think much of on bipedal characters.
performance - you wouldn't rig a golden retriever the same way you would a 12 tonne dinosaur
anatomy - sometimes you need to break the rules a bit from an anatomical standpoint in order to get the desired deformations and look from the creature.
controls - keep them simple and to as little amount as possible, allow the animators freedom to turn on extra controls but never give them 60 controls to begin with or you'll find them pulling their hair out.
motion - just like anatomy, you gotta know how the character moves and you need to study reference to a tee before you place the first joint or step forward.
Some areas to pay attention to on quadrupeds:


scapula region - this specifically applies to feline creatures as they have a very complex scapula setup that requires some pretty smart engineering to really nail it. Have a look at the chronicles of narnia for some good examples.
knee region - another area I sometimes see go overlooked, I prefer to use a double joint (kneeTop, kneeLow) when working with knees on quadrupeds because it allows me to get a nicer compression in the back of the leg while maintaining volume in the knee cap.
ankle/feet - always a pain, weight distribution is critical for quadrupeds and the distribution in the feet (toe spread, compression) is what sells the weight of a creature (you don't want to have that big tyranosaurus look like he's a ballerina prancing about on air now do you?). The other caveat to the feet on quadrupeds, specifically dinosaurs is the 'stick' of the claws when lifting off the ground, the way they always peel off like velcro on some creatures (splineIK to the rescue here!)
some requests I've heard frequently:


independent motion of spine and hips, really helps the animators out by not having to counter-animate a large hulking creature. A reverse pelvis setup helps immensely when working with the animators, helps to separate the rear from the torso and segment the motion.
directional guides, show the angle the eye is pointing towards, where the knee or arm pole vector is pointing etc.

That's just some of my experience and thoughts to throw out on the table.

-s

eek
04-07-2007, 12:09 AM
I apply the same rules i use on bipeds on quadraped, rules i learnt in ancient tibet 7 million years ago! j/k :) In the following order:


Torso Control
Independant Hips
Independant chest that drives neck
Independant head orientation via torso, reverse ik position.*
*The head follows with the neck, in position space but its orientation follows torso. When you adjust the head, the neck follows with it. Basically like a real human, move the chest neck will follow but head stays locked orientationally, adjust the torso everything moves/rotates with it.

Ik/fk feet
foot lock fk on the forelegs
*fk tail
*Driven ik if needed. I set that up on a rat tail basically ik handles down the chain of the tail, parented from tip to pelvis, with z positon turned of in the hierachal inheritancy panel. - This allowed for control of the tail but also maintained it being 'glued' to the floor.

Standard reverse/natural foot: ankle,BoF and toe.
Notes:

The shoulder rotates about its center.
Add control 'bias' for fixing twist problems.

Addtional Ideas:

surface lock of paws/hoofs, to a ground plane/surface for walking on uneven ground etc? could use simple ray detection for this.

Ability to roll entire character onto its back, needed for quadrapeds like horses when they need to get up.

Realtime dynamic flappy bits: ears, tails, tongue,fat etc - easy to script with when constructs, time callbacks or even a timer.

Key offset baking, hierachal based pasting of keys from one foot to another, relative to a root in position space and orientationally in local space.

Key offset fixing of root to children i.e getting back to its original position without destroying the animation. ( this is a big problem that came up recently and very hard to fix)

Fun & possibly stupid ideas:

Distance based 'bite' control of target object, i.e automated biting of object based on distance of it to jaws.

cheers,

dude5487
07-13-2007, 06:47 AM
I thought for sure I had said this before but there is no post of me responding. I wanted to say thank you to both of you for all the info you have provided!

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