Shoulder and Hip bones

[ggoblin]

Hi, as a novice I need basic advice on character bone rigging.

I see some animators using a very basic bone structure effectively:

master <-- abdomen <-- chest <-neck <-- head

master <-- left upper leg <-- left lower leg <-- left foot <-- left foot toe (same for right)

chest <-- left upper arm <-- left lower arm <-- left hand (same for right)

Others include left/right hip bones and left /right shoulder bones:

master <- left hip <- left upper leg <- left lower leg <- left foot <- left foot toe

chest <- left shoulder <- left upper arm <- left lower arm <- left hand

My Questions:

1. What are the advantages of including the extra bones? Are they, for example needed for better walk cycles eg realistic hip sway and shoulder tilting?

2. What are the costs of including the extra bones? Do they make basic animation, where they might not be needed, more complicated to achieve?

3. Is it better to stick to the basic bone structure if your animation is simple, and add the extra bones later if needed. Or is it better to include them at the start just in case you need them later?

Thank you for your help

[synthsin75]

Shoulder bones are useful, it you want a more realistic stretching of the torso when raising the arm. As long as you use a sensible angle constraints, they shouldn't hinder animation any.
While more cartoony styles likely don't need them, it can be a headache adding them later. Do some tests or storyboard to see what you'll be needing.

For hips, I'd only use one hip bone for both legs, as the hip is one solid bone. That's plenty for sway, and it's hard to do sway without a hip bone. But again, plenty of animations have no hip sway. Depends on the style.

[slowtiger]

Shoulder and hip bones are not only useful for movement but also for more expressive poses - think of shifting weight from supporting leg to free leg, or a shrug. Make it a habit to include them all the time - you can still set their constraint to 0 if you don't need them in a scene.

[Daxel]

All good advices.

I would add that you are not limited to bone animation, so don't forget that you can achieve any pose with point animation even if you lack some bones.

For example, if you don't have shoulder bones but you want to move the shoulders, its still easy to translate your arm bones to the desired position and then adjust the torso points with the magnet tool. It takes seconds and it's more versatile than what a bone can do, specially if you are creating a rig that is able to turn. Those shoulder bones can get in the way when you are trying to include a turn to the side view, as you can imagine.

Edit: Now that I remember, the last time I used shoulder bones in a 360º rig I think I just didn't move them in the smart action for the turn to the side, so it wasn't a problem. I just remember moving the arms with the transform bones tool instead of the manipulate bones tool, to avoid moving those shoulder bones via inverse kinematics while the character was in side view. I would like to know how other users deal with them in a turn.

[Greenlaw]

FWIW, I don't normally bother with clavicle or hip bones in a Moho rig. This is mostly because I'm typically rigging 'cartoony' designs where I work, and I find I can still get a lot of the expressiveness from a rig without them. But mostly it's because adding these bones complicates being able to smoothly turn a character 360 degrees. To see what I mean, check out my most recent demo reels (2017-2020); none of the Moho rigged characters featured on the reels have clavicle or hip bones.

That said, I agree that clavicle bones can allow you to bring more realism to a character. But before you start rigging, you should consider the design of the character and how much realism is appropriate for the style of the animation.

Personally, I'm more likely to include clavicle bones in a one-off (i.e., shot-specific) rig than I would in a multipurpose rig.

But then again...with the new Vitruvian bones system, it's possible to have both clavicle and non-clavicle setups in a rig. Soooo...I may need to reconsider some of my 'go to' rigging practices. TBD.

Sorry, I didn't mean to muddy the waters, but these are a few useful things to think about. I suggest working with both types of setups and decide then which works best for your style of animation.

Good luck and hope this helps!

[Greenlaw]

I forgot to mention the hip bone. I don't often use a hip bone but it depends on the character design. If the character is very short and squat, it probably does not get a hip bone. Taller characters are more likely to have it.

When I do add the hip bone, it's typically a single inverted bone hanging off the character's root bone, and it's mainly used anchor the pelvic region as I bend the spine or to shake the character's butt. (Man, this job can get weird.)

[ggoblin]

Thank you everyone for your great advice.

As a beginner there is a lot to learn, I really appreciate you sharing your invaluable experience, it really helps.

Some of it is above my head for now. I haven't done any body turns so didn't think of its implications. I just assumed its just adding an extra bone to the arm hierarchy and an extra bone to the leg hierarchy and would deal with it the same. But I'm guessing that the issue is that, unlike the arms and legs, the shoulder and hip bones are horizontal and hence it will entail bone resizing when turning the body and that will complicate things?

I did try shoulder bones (following the advice of imposing angle constraints) and they did add benefit to the movement - less doll like action when the arms are raised (I had to point bind the two shoulder bones to the points at the top of the thorax, with the rest of the thorax/abdomen bones (chest, abdomen, and 2 hip bones) in same layer using 'selected bones for flexi-binding').

As for hip bones, they seem to add an extra motion to the legs - a bit weird motion at times, not sure if its helpful at this stage - need to experiment more, perhaps put some angle constraints?. But I think having them makes the abdomen bone more responsive in helping bend the body ( the 3 bones are linked together like a star with 120 degree separation rest angle) ? I wonder if this is what Greenlaw refers to - 'anchor the pelvic region' ?

In my set up I have split the upper body and lower body bone hierarchies with no direct parenting between them. Each hierarchy parents to the master bone, so there is no direct linkage between the abdomen bone and the chest bone. Is this the correct approach?

Daxel, I am intrigued by your suggestion for using point animation for shoulder and hip movement. Would I for example add the point animation for hip sway when setting up the action for a walk cycle, or would that be part of a smart bone action for the thigh bone movement in general which would then automatically kick in during any walk cycle? Also I was interested in what you said about not moving the shoulder bones during a 360 degree rig, does that mean that you couldn't then use shoulder bones (and hence IK for arms) during the the other angles of the body?

Thank you for your help everyone.

[Daxel]

As a beginner there is a lot to learn, I really appreciate you sharing your invaluable experience, it really helps.

Moho is very powerful so there are a lot of different things that you can do using different combinations of its rigging tools in different ways. Try to be comfortable with one level of complexity at a time, and you'll be fine. Some people come to Moho atracted to the 360º multipurpose rigs and end burned out trying to learn everything at the same time.

In my set up I have split the upper body and lower body bone hierarchies with no direct parenting between them. Each hierarchy parents to the master bone, so there is no direct linkage between the abdomen bone and the chest bone. Is this the correct approach?

I like that approach and it's probably the most common one. You have a Root or Main Bone between the legs and the torso, and you use that bone to translate the entire character.
I like to have this Main bone looking straight to the left, between the Pelvis bone (only one, as Wes suggested) looking straight down and the LowerBack bone looking up. If you hold the legs with target bones, you can dance pretty well rotating the Pelvis bone, for example. Both legs are parented to the Pelvis bone but not physically conected to it.

Daxel, I am intrigued by your suggestion for using point animation for shoulder and hip movement. Would I for example add the point animation for hip sway when setting up the action for a walk cycle, or would that be part of a smart bone action for the thigh bone movement in general which would then automatically kick in during any walk cycle? Also I was interested in what you said about not moving the shoulder bones during a 360 degree rig, does that mean that you couldn't then use shoulder bones (and hence IK for arms) during the the other angles of the body?

For the hip I always use a Pelvis bone, there is no point in using two and I don't see any reason to not use one. You don't need to animate that bone at all while making a turn to the side, so it doesn't have the problem that the shoulder bones have. Also it's only one and big solid structure, so it's simpler to animate with a bone.

The shoulder bones are the clavicles, one for each shoulder, and have a more organic movement that deforms the torso, usually when you move the arms up and down. If I want to animate a shoulder shrug, I would translate and animate the arm bones first, as the rest of the bones, and then I would use the magnet tool to animate the parts of the torso that are moved by the clavicles to match the arm translation organically.

As GreenLaw, I see the convenience of having clavicles in a front rig, for a more automatic movement, but they kind of get in the way when making a more complex rig able to turn to the side, because the clavicles would point one to the camera and the other to the opposite direction while the character is looking to the side.

[Greenlaw]

I agree with Daxel on all of these points.

For the hips, yes, only one bone is needed. The hip bone (in my rigs anyway) is mainly there hold the artwork in place, so it's rarely animated. But when I want to rotate it, the inverted setup I described is there so I can counter rotate it to the spine without affecting the bones above the root. Many of the characters I've created don't even have this bone but it's easy enough to add when I need it.

Clavical bones, as synthsin75 mentioned earlier, are more difficult to add after you've rigged the arms, so you should decide if you need them before you get to that point. If you're animating simpler or cartoony characters, chances are that you don't need them; there are other ways to get a similar effect without complicating the rig. But if the character is designed to be realistic, you might want them.

Sometimes I'll do a couple versions of a character: a version with special features I might use only occasionally, and another general purpose version with only the features I need most of the time. I find this works better for me than creating a single feature-heavy all-purpose rig that does everything I can imagine but is a pain in the butt to animate with.

[synthsin75]

For example, if you don't have shoulder bones but you want to move the shoulders, its still easy to translate your arm bones to the desired position and then adjust the torso points with the magnet tool. It takes seconds and it's more versatile than what a bone can do, specially if you are creating a rig that is able to turn. Those shoulder bones can get in the way when you are trying to include a turn to the side view, as you can imagine.

Edit: Now that I remember, the last time I used shoulder bones in a 360º rig I think I just didn't move them in the smart action for the turn to the side, so it wasn't a problem. I just remember moving the arms with the transform bones tool instead of the manipulate bones tool, to avoid moving those shoulder bones via inverse kinematics while the character was in side view. I would like to know how other users deal with them in a turn.

Translating upper arm bones instead of clavicle bones is a good tip, especially for lesser used expressions on a more cartoony rig.

Yeah, I'd be apt to just translate the upper arm bone along the clavicle bone (or just scale the clavicle) for a turn. I'd still want the shoulder movement at different angles.

[ggoblin]

Thank you so much for the great tips. I replaced the two hip bones with one bone pointing straight down, and it got rid of the weird movement I had before. I think with one pelvis bone, whatever motion I give one leg, it automatically compensates by taking from the other leg and hence the motion is more balanced, less weird.

As I'm just learning and experimenting right now, I don't have a specific project so everything tends to be 'multipurpose' experimenting rather than a project needs driven approach. But I really appreciate the practical advice that it is often better to have several rigs customised to specific tasks, rather than one general purpose rig which is in theory can do everything but in practice is too cumbersome to use for anything other than demos.

At this stage I'm just trying to get a feel for where the boundaries of Moho are so I can judge where best to utilise it and how complex a given task is going to get. Ideally I just want to learn one package, learn it really well, and then use it for everything from character animation, explainer videos, text animation - motion graphics - transition special effects, even 2d vector drawing.. of course thats not going to be possible but its good to get a feel for Moho's comfort zone.

Thank you