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dude5487
04-02-2007, 04:34 AM
Can anyone give me an explanation on the benefits of doing a rig with a double elbow set up?

Thank you very much!

eek
04-02-2007, 06:05 AM
Are you talking about the double ik setup in the arm to allow the elbow to be pinned?

dude5487
04-02-2007, 06:44 AM
Hey hows it going? What I mean is two joints side by side right at the elbow, the last time I saw it was on the super toon series of tutorials before I just saw it on Aaron Holly's "Rigging for Feature Animation" training. That make sense?

"Are you talking about the double ik setup in the arm to allow the elbow to be pinned?"

Would you be able to direct me to some more information in that?

Thanks!

Leionaaad
04-02-2007, 07:19 AM
aren't you referring to the 3 jointchain setup (probably were 3 chains, two of the chains being in the same place)?
If this is the case, is for Ik/Fk switching

dude5487
04-02-2007, 07:39 AM
No that is not what I am referring too. Though that is what I am working on right now haha.

What I am talking about is this. See attached images.

Celation
04-03-2007, 04:36 PM
Yes - this is pretty useful in knees.

It allows for the fact that certain hinge joints aren't actually rotating around a fixed point. If you look at anatomical illustrations of legs, and look at a knee in articulation, you'll see that it's possible to have the two bones of the leg almost parallel when the knee is bent. This is because the end of the femur is shaped so as to push the point of rotation outwards the further the knee bends.

Double joints in rigs help to add this offset. It's not exactly true to life, but it's better than a single hinge joint, and stops the squashing up of the knee as it reaches its most bent poses.

Personally, I wouldn't tend to use it for an elbow, as the hinge joint there *is* almost a true hinge joint.

C.

dude5487
04-03-2007, 06:25 PM
Thank you for the response and the information.

You say that you wouldnt do a double joint at the elbow because it is almost a true hinge joint? I can understand that though at the same time dont you think the benefits from the deformation is there as it is for the knee?

eek
04-03-2007, 07:09 PM
No that is not what I am referring too. Though that is what I am working on right now haha.

What I am talking about is this. See attached images.

Do the joint chains stretch with this method?

dude5487
04-03-2007, 07:55 PM
No I havent seen any stretching along the chain. I have an IK set up at home on mine and it works just like anything else except it looks a bit better with the double, IMO, especially on the knee, like Celation touched on.

Though right now I am trying to set up the FK controls for the double joints on the arm and leg and im sure that might tell a diff story of what to do and what not to do.

LucentDreams
04-04-2007, 05:17 AM
Aarons setup has them stretching.

the key advantage to the double joint setup is when doing severe bends into the 150 or possibly more range. with a single joint the mass starts to collapse in on itself where the weighting on two joints allows for the limb to bend into itself without collapsing geometry into each other. I could see using it on knees, but on elbows I'd more likely rely on muscles or morphs

dude5487
04-04-2007, 05:32 AM
Thx for the reply. I didnt know Aaron's set up had them stretching, I stand corrected. As it stands though if you have them in there with stretching is it a horrible thing? Again I am seeing from your response a lot of positive feedback about the knees but not so much the elbow, its an iffy thing.

This may help though it may not, the rig I am making is a more of a cartoonish rig. Not really an anatomically correct human. I had seen this originally in the Super Toon kit and given what kind of character I am making I wanted to simulate that set up, then when I recently saw Aaron Holly perform something similar it really got me going.

Is there anyone out there who has used this on a "cartoon" character before? In particular using an IK FK blend set up.

I appreciate all input given thus far! Keep it coming if you can :)

Josh

Celation
04-04-2007, 10:19 AM
You say that you wouldnt do a double joint at the elbow because it is almost a true hinge joint? I can understand that though at the same time dont you think the benefits from the deformation is there as it is for the knee?

The elbow has always seemed like more of a simple hinge joint in terms of rotation, perhaps due to the extra stuff it has to do with twisting along the forearm. That said, many people do use double joints at the elbow for exactly that reason - to help with deformation.

To me, there is a fair amount of compression at the elbow which is due to the fixed pivot point. This compression seems to be a natural effect of the joint, and I deal with it in other ways (clusters to emulate muscle squashing, etc.) rather than changing the rotation axis.

This thread's got me thinking, though. I'll give it a test next time I'm rigging one.

dude5487
04-04-2007, 10:38 AM
Its got me really interested for sure and I look forward to what you come up with.

eek
04-04-2007, 03:15 PM
Aarons setup has them stretching.

the key advantage to the double joint setup is when doing severe bends into the 150 or possibly more range. with a single joint the mass starts to collapse in on itself where the weighting on two joints allows for the limb to bend into itself without collapsing geometry into each other. I could see using it on knees, but on elbows I'd more likely rely on muscles or morphs


One way to solve this would be to use spherical skinning rather than linear, im going to start looking into this as the interpolation of vertices to there respective bones is quaternion, i.e slerp rather than lerp. Crytek uses this method, and it allows for good artistic control, with solid results in combination with twist and fix bones.

cheers,

LucentDreams
04-04-2007, 05:19 PM
if you want a comparison I can make you one in a few minutes, Cinema 4D r10 now has both linear and spherical (quaternion) as well as a blend skin mode which allows you to use either a slider or even vertex maps to blend between the two skin types.

eek
04-04-2007, 06:20 PM
if you want a comparison I can make you one in a few minutes, Cinema 4D r10 now has both linear and spherical (quaternion) as well as a blend skin mode which allows you to use either a slider or even vertex maps to blend between the two skin types.

damn! thats cool!

LucentDreams
04-04-2007, 07:40 PM
http://www.kaithestuffguy.com/images/skintypes.jpg

dude5487
04-04-2007, 10:05 PM
That looks awesome thats the kind of look I want to get. Though I am not sure if Maya has all of the options what you just shown has. Thats in C4D you say? What else can that program do? lol

LucentDreams
04-04-2007, 11:55 PM
don't want to get into a sale pitch kinda thing, but lets just say much of Aaron's workflow can be done much much faster in cinema. That said a fair bit of it could be done a little faster in maya too imo. He teaches good concepts and a good rig, but a lot of his stuff is very tedious manual imo.

For example in one part where he sets up his joints in the centers of the volumes for his arm he:

1)select an edge loop at the shoulder
2)converts it to a point loop
3)creates a cluster
4)selects an edge loop at the elbow
5)converts it to a point loop
6)creates a cluster
7)creates an edge loop a little lower on the elbow
8)converts it to a point loop
9)creates a cluster
10)Creates an edge loop at the wrist
11)converts it to a point loop
12)creates a cluster
13 and 14 and 15...)Then he goes about making splines to draw the joints on and what not.

In cinema:
1)in Edge, poly, or point mode one can select loops, and you select al four loops at once, shoulder elbow1 elbow2, and wrist
2)While holding the shift key you use a command called "Convert selection to joints",
3)simply make the hierarchy with the 4 separate joints, child the wrist to elbow2, elbow 2 to elbow 1, and elbow 1 to shoulder.
4)run the Align command.


Without the shift key, the "Convert selection to joints" would make a single joint centered on the center of the entire selected volume, but by using shift it recognizes each non connected selection (loops with non selected polys in between) and creates a joint at the center of each selections volume.


back on topic, you can see how the 2 joint method can help preserve volumes a little better, and oyu can single how the single joint with spherical actually bulges out too much. But really I think I shoudl do some more testing now as I must say that the single joint with the 50% blend is probably the nicest deformation for absolutely no manual weighting.

Another issue with spherical skin types is they are noticably slower, not drastically as to render them a last resort, but defintely makes an already slow rig impossible to animate in real time. the blend mode suffers the same speed as the spherical mode, but surprisingly no additional speed hit, I guess it must solve the linear calculations in achieving the spherical perhaps. Nice thing with cinema's system is that the skin uses a simple integer drodown to switch between the three modes seemlessly so one can animate with the linear deformations, then whenever its time to do a render, even aplayblast, they can switch it to spherical or blended to get the proper final result. In my tests the differences in deformation are small enough that it shouldn't affect how the essence pose looks or anything like that, just how the elbow bugles or forearms twists. Oh, thats another advantage to spherical skins, no collapsing when a join twists. however in cinema's there is an issue where if twisted too far it will flip (basically same principle idea as an IK spline going past 180 if its not using a ribbon technique)

dude5487
04-05-2007, 12:40 PM
Thanks for the detailed write up :). I sounds like its a really great program. I will have to take to learning it this summer. I know this is off topic but are you aware of any good training material for the app?

Thanks again.

Josh

LucentDreams
04-05-2007, 01:41 PM
Its your thread if you dont mind it being off topic thats okay.

for training, c4dcafe.com has a lot of free videos, and www.cineveristy.com is the official maxon training resource. their also looking at starting masterclasses possibly at siggraph this year.

theres not much on rigging on cineversity yet as I'm still making the series. there not a lot of training for rigging in cinema, and especially not in R10 with the new CA tools.

Lyr
04-05-2007, 05:44 PM
Anyone tried using this yet http://www.highend3d.com/maya/downloads/plugins/animation/MayaSkinClusterDq-4625.html

Looks similiar to that spherical skinning in C4D. Looks like there is source for the plugin available as well.

LucentDreams
04-05-2007, 06:38 PM
yes spherical is the same thing as quaternion skinning.

dude5487
04-05-2007, 08:09 PM
Thanks for the info I just glanced through the sites they look pretty good. As for rigging what your saying is pretty much learn your way through from concepts you've known before?

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