Character Rigging: T-Pose Question

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Old 12 December 2012   #1
Character Rigging: T-Pose Question

I'm considering a character model on turbosquid that has the arms at roughly a 45 degree angle (in relation to the chest/body). In all the tutorials I've watched on rigging the arms are closer to a 90 degree angle (the classic T-Pose).

Does this matter? I'm guessing the T-Pose is ideal to start with, but will I run into problems rigging a character that has the arms at a 45 degree angle?

Just curious.

Thanks.
 
Old 12 December 2012   #2
I think that the reason that the 45-degree pose has become the new standard over the classic T-pose is that it makes the shoulders easier to deal with. If you raise your own arms at your sides, you'll notice that you can raise them to about 45 degrees without requiring any shoulder movement. But anything above 45 degrees will be handled entirely by the shoulder joint.

What ended up happening with T-poses is that inexperienced riggers would treat the shoulders as though they were already in a "rest" position (since this was the base model), which would lead to very hunched poses when the arms were at their sides.

Since an animated character's arms are at or below 45 degrees most of the time, it makes sense to model the shoulders in the rest position and rig/animate them up from there, rather than modeling the shoulders in a raised position and trying to extrapolate what the rest pose would be like.

Again, an experienced rigger can handle either pose, but all things considered it's generally easier to rig from a relaxed 45-degree pose than from a T pose.
 
Old 12 December 2012   #3
It's something people debate about but really either will work IMO.

The advantages of T-pose are that the joints are easier to place and it's a good starting point when working with mocap, while it can be argued that the A-pose is a better starting position for deformations as it's closer to the average pose of the arms (really our characters spend very little time with their hands high above their heads generally).
One thing with the A-pose though is that generally the autoskinning will grab more of the torso and assign weighting to the arm joints, but it's never really been an issue to me really as I always finesse the weighting a lot anyway and there are usually issues with the armpit area no matter what pose you start with.

I have a great book here 'Advanced Rigging and Deformations' that discusses having a separate 'bind pose' and 'rig pose', where the character is skinned in the A-pose and then the rig is moved into the T-pose (usually with some corrective work on the mesh) so that the controllers can have their coordinates frozen and still give predictable f-curves for the animator. On most projects though that's likely overkill, but I would advise not freezing coordinates on the IK hand controllers in the A-pose as it does get confusing in the curves then (Y is not really Y and that kind of thing).

HTH,
Cheers,
Brian

Last edited by Horganovski : 12 December 2012 at 05:51 PM.
 
Old 12 December 2012   #4
I'm definitely not an experienced rigger. Not by a long shot! So this information is extremely helpful & insightful. I think I'll go ahead and purchase the A-Pose character on turbosquid. It's a super basic & simple mesh (the topology looks good!), so hopefully I won't have too many problems with it.

Thanks tons.
 
Old 12 December 2012   #5
Originally Posted by spirozero: I think I'll go ahead and purchase the A-Pose character on turbosquid. It's a super basic & simple mesh (the topology looks good!)


There is a good basic human model that is part of the v14 sculpting base mesh pre-sets. there is a male and a female (and a frog!). I am doing a project now where I made my first fully rigged and walking character, and I started with the pre-set male model. Extra help came from Brian's helpful video tutorials.
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Old 12 December 2012   #6
Brian pretty much explained the differences between both poses, but there's one point I wanted to clarify:
Originally Posted by Horganovski: One thing with the A-pose though is that generally the autoskinning will grab more of the torso and assign weighting to the arm joints, but it's never really been an issue to me really as I always finesse the weighting a lot anyway and there are usually issues with the armpit area no matter what pose you start with.


You can set your autoweighting to "visibility" and it will not grab the points from the torso and when assigning influences on the arm joints (basically, it only take into consideration what the joint can "see" within a certain radius).
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Old 12 December 2012   #7
Originally Posted by Ernest Burden: There is a good basic human model that is part of the v14 sculpting base mesh pre-sets.


Bummer. Just saw this. I installed R14 last week, so I'll definitely look for the male model you're referring to. Thanks.

Still, I already purchased this inexpensive model from turbosquid ...



My follow-up question for future reference: what about the legs? This model's legs seem a little too spread out? Would you guys recommended having the legs be more vertical before rigging?
 
Old 12 December 2012   #8
https://vimeo.com/11899396

Check out this 3 part series. it's about an hour and a half that will provide you with a wealth of good information and things to consider about a model / how it should lend itself to animation.

Another one to check out for the obsessive would be hippydrome's stuff...although that is not yet complete.
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Old 12 December 2012   #9
Originally Posted by Ernest Burden: There is a good basic human model that is part of the v14 sculpting base mesh pre-sets.


Those meshes are suitable for sculpting due to their uniformity and density, they are not really good for rigging. For best result when rigging and animating you want to have mesh with less geometry and with strategically arranged loops which have future deformations in mind. Loops should be tighter where extreme stretching is expected and wider in areas of high contraction.

As far as the base pose is concerned, I prefer relaxed A pose since this enables me to get good shoulder deformations often without corrective shape, but most of the clients provide their "animation ready" models in T- pose so I reckon it is more popular base pose.

Fluffouille mentioned visibility option when weighting. Although that can be a solution I hate the fact that it leaves stray points and auto weighting is something I also began to avoid. I found that manual selection blocking, bleeding&smoothing and a bit of refining does the job really well

Cheers
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Old 12 December 2012   #10
When it comes to weighting, rarely do I use any auto mapping. Perhaps I'll keep some areas that need to blend up to four joints, but I'll try always let it auto-weight and see if there's anything I can keep, then just either correct by painting absolute values around loops, sometimes manually graduating them (e.g. shoulder to elbow: 100%, 75%, 50%, then 25%), then putting the character in some extreme poses to see where it come apart and correct by painting with auto normalize activated (it almost always is anyhow), then some smoothing.

As far as the T vs. A pose, I prefer the A for the end result, but I'm doing some work in Unity 4, and their new Mecanim system requires a T-Pose.

It is a bit easier to rig a T just because everything lines up to the world axis, but yeh, the shoulders, armpit, clavicles, and deltoid/trapezius are always a pain to get right, unless the edge loops are set up for it. Sometimes hardly then, though. Lots of tweaking the weights, mesh and rig there.

P.S. I'd straighten the legs in a standing pose if possible.
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Old 12 December 2012   #11
Originally Posted by hsrdelic: Those meshes are suitable for sculpting due to their uniformity and density, they are not really good for rigging...


Which I didn't know, will take time to learn the fine points. Still, I did use the sculpting base male and things have gone well enough.
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Acme Digital
 
Old 12 December 2012   #12
Originally Posted by hsrdelic: Those meshes are suitable for sculpting due to their uniformity and density, they are not really good for rigging. For best result when rigging and animating you want to have mesh with less geometry and with strategically arranged loops which have future deformations in mind. Loops should be tighter where extreme stretching is expected and wider in areas of high contraction.


Not necessarily. Even for rigging, you want fairly uniform face sizes. Whether that be a hi res or lo res, that's up to you, but uniformity is important for weight falloffs. Just like the placement of poles, and the layout of the loops.
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Old 12 December 2012   #13
Originally Posted by xfon5168: Not necessarily. Even for rigging, you want fairly uniform face sizes. Whether that be a hi res or lo res, that's up to you, but uniformity is important for weight falloffs. Just like the placement of poles, and the layout of the loops.


Indeed, I used to always try to keep the poly count as low as possible but I've seen plenty of examples of meshes that will actually deform better when subdivided once. I guess there's more to work with in terms of weighting falloff and you can always add corrective morphs to maintain volume when needed. If you look at wireframes from feature-level character meshes (I'm sure Bret has hands on experience here) you'll see they are often more detailed than you might think, especially when it comes to realistic animal and creature models so that they can get in nice folds, muscle deformation etc.

Here's an example of a pretty optimal mesh IMO. This was modeled and rigged by the awesome Victor Vinyals (it's one of the iAnimate rigs). There's a lot of blend shapes (morphs) underneath the skinning that help the deformations in certain poses but in general the uniformity of the mesh really helps. I made a mod of this rig that had controls for the arms and leg muscles so that they can bulge and the detail in the mesh there really helped for that.


Cheers,
Brian

Last edited by Horganovski : 12 December 2012 at 11:20 PM.
 
Old 12 December 2012   #14
The loops are set up nicely for deformation/articulation in that mesh.
I think what hsrdelic meant, was that meshes for sculpting do not benefit from edge loops set up for articulation. For sculpting uniformity is important - nothing else. Edge loops, like the ones shown in your mesh, will/can be troublesome while sculpting, as the poles will pinch when subdivided. Almost impossible to smooth out. So to conclude, uniformity and edge flow is important for rigging - sculpting is better off with uniformity alone in the base mesh. You can always set up the loops for articulation later when retopologizing.
 
Old 12 December 2012   #15
Good points, with the mesh above it's supposed to be a more stylized toon-style character so I guess sculpting on that mesh was never accounted for.

Cheers,
Brian
 
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