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Steve Warner
04-12-2005, 01:44 AM
Okay, rigging & animation gurus. I've got some questions for you.

1. How many of you use IK on your arm setups?

2. For those using IK on your arm setups, how many use rotation limits to keep the IK in check? If you don't use rotation limits, why not?

3. Is it possible to fully rig a character for animation and not use expressions or motion plugins?

4. If the answer to #3 is no, then what types of expressions and motion plugins should I start looking into to get the job done?

Thanks for your help in advance!

Steve

Carm3D
04-12-2005, 02:06 AM
I use IK arms. I tried FK arms but I like IK better for me. It's all very much up to taste.

I don't generally use rotation limits. I pre-bend the joints so the joint bending the wrong way is not a issue, and I guess I animate carefully enough to where it's not necessary.

Is it possible to fully rig a character for animation and not use expressions or motion plugins?

Heck if I know.. I use alot of expressions.

If the answer to #3 is no, then what types of expressions and motion plugins should I start looking into to get the job done?

this page (http://www.carm3d.net/3D_Stuff.htm) has two rigging tutorials that talk about expressions I use (among other things).

T4D
04-12-2005, 01:05 PM
Okay, rigging & animation gurus. I've got some questions for you.

1. How many of you use IK on your arm setups?

2. For those using IK on your arm setups, how many use rotation limits to keep the IK in check? If you don't use rotation limits, why not?

3. Is it possible to fully rig a character for animation and not use expressions or motion plugins?

4. If the answer to #3 is no, then what types of expressions and motion plugins should I start looking into to get the job done?

Thanks for your help in advance!

Steve

1/ I Only uses Ik on arms If the character is holding something with both hands or interacting with the scene in some way I personally try to uses FK arms as much as i can.

you get better elbow movement and placement and much better control of bending the arms. they are more channels to key and control but you avoid alot of problems with LW's IK.

2/ I see no real need to add limits straight off Prebending is a must and limit you bones to one channel controled by IK ( if needed make small bones in the middle )

But Sure if i get the odd flipping or unwanted movement I add limits to the lowarms first and if the problem keeps happening i add limits to the upper arm ( I don't have to do this much at all but i do remember doing it)

3/ YES I never uses them for the body AT ALL !!
the only time i uses expressions or motion plugin is for IK/FK Blending ( i only used that if I have no other option have free video on my site for that ) or Joystick face rigs That's IT !!
Tho I uses Targeting for better shoulder deformation sometimes

IK slows down LW enough when you get 3 or 4 characters in a scene you really get slow down with IK so i don't add anything for this reason

PLUS i HATE it when i can't control/key things that are control by expression/plugins it's a pet hate of mine,
Animators animate you don't get the computer to animate for you, it's not the artist you arehttp://cgtalk.com/images/smilies/buttrock.gif.

exsample - i used to have auto toe bend on my feet ( using targeting ) but as time has gone by I now prefer to kill all that stuff and just key the toe when i have to, you can get that toon toe flip as you walk ( and expressions/ plugins just can't do that )

4 / No don't do it !!! http://cgtalk.com/images/smilies/grin.gif

Celshader
04-12-2005, 02:17 PM
Okay, rigging & animation gurus. I've got some questions for you.

1. How many of you use IK on your arm setups?

2. For those using IK on your arm setups, how many use rotation limits to keep the IK in check? If you don't use rotation limits, why not?

3. Is it possible to fully rig a character for animation and not use expressions or motion plugins?

4. If the answer to #3 is no, then what types of expressions and motion plugins should I start looking into to get the job done?

Thanks for your help in advance!

Steve

1) I use IK on my arm setups. That way I can get the pose I want with fewer keys.

2) I do not use any rotational limits. I'll second T4D's praise of "prebending." IK does its darndest to maintain the earliest pose in the scene, so I just make sure to key the IK-controlled channels on the earliest negative frame of the scene, to "program" the values that IK will try to maintain.

3) Yes, but I still write and use expressions for work that I do not want to do.

4) I use multiple bones in the arms and forearms of my characters to simulate torsion. Rather than key each of these bones by hand, I use expressions to automate their bank channels. Those are the only expressions I have used for my recent character setups.

Use whatever rig setup you feel most comfortable animating, though.

Mikado
04-12-2005, 02:24 PM
1. Definitely. One of major features of a good rig is never needing to counteranimate (while this isn't always entirely possible it's good to try and minimize it). This means when you move one bone, the descendant hierarchy should, as much as possible, retain its pose. Good IK arms provide this as well as sidestepping gimbal lock issues. That being said, an uncontrollable IK setup is worse than nothing. Note that in a full rig, the arm IK targets are rarely left at the root of the scene (or even the object). Most rigs I've seen and used have a hierarchy of "waist" nulls, and the arm targets are typically children of one of them.

It should be pointed out that using IK arms means the animator needs to do some more attentive animating. Merely setting two keys on an IK target as it moves will make for icky motion. Typically 3 keys per move are needed for a nice arc. With FK, one can sometimes get away with 2 keys to get arcing, albeit floaty, motion.

2. None. Rotation limits aren't a very good way to prevent IK flipping. 2D chains (IK on pitch only) with pole vector constraints work quite a bit better and have the benefit of being fast and stable during posing AND playback. 2d pole vector chains also don't need extreme prebending to work correctly either; typically a few degrees will do. I've seen some polevector setups that work in OEM LW (LW without plugins), but they can be a bit finicky ~ which more or less defeats the purpose. If one is willing to accept motion modifiers as a necessary evil, there are some easier alternatives.

3. Undoubtedly. However many plugins available for LW simply duplicate functionality that exists in the "stock" installation of other more expensive packages. If one can accomplish a goal with either a single (presumably free) plugin, or with a ton of helper bones and mystery nulls, it's not a difficult choice to make. In addition, some of the "built-in" functionality of lightwave doesn't, in fact, work as desired. For example "Match Goal Orientation" isn't recognized when setting rest positions, but motion modifiers are. The built in "Target" command doesn't accept an "up-vector" target, which causes a loss of control near the gimbal lock axis. The biggest downfall to motion modifiers is they can be tricky to apply through scripting and they may not be handled correctly when mirroring a hierarchy (which means they would need to be manually re-applied to the duplicated bones). Personally I find this to be an acceptable trade-off.

4. I ended up writing my own motion modifier plugins to accomplish what I want to do, but I find most of them are simple constraints that exist in other packages: nothing revolutionary or even terribly difficult to write (one might ask WHY they haven't already been implemented in the OEM LW then). The ones I can't live without now are RV_Spine for stable curve-based spline IK, RV_Orient for polevector constraints and up-vector targeting, RV_Pin for parenting that disregards the parent's rotation - This might be available in one of the "follower" type plugins but I've never found one that does what I want.

If you already KNOW what you want to do, and the tools don't seem to exist, you can either try and cobble together the tool you want from the tools you HAVE; you can acquire (build or download) the tool you need; or you can suffer without it. The latter isn't really a very good option.

//\

ericsmith
04-12-2005, 04:53 PM
1. IK on arms: Definitely. I have two tricks to making this work effectively. The first is to create a parent structure that makes the hand goals follow the torso. This prevents the arms from looking too floppy when moving the character around. The second is to have good elbow control. Instead of trying to have a multi-goal chain on the arm, I just control the elbow by rotating the bicep and shoulder on their bank channels. It works flawlessly, and it more realistically simulates the way real human anatomy works.

2. Limits: I agree with everyone else, and generally prebending prevents the needs for limits, but personally, I put them in as one last safeguard that my character won't spaz out under some extreme circumstance.

3. Expressions: I definitely would not enjoy animating without expressions on my rig. My personal philiosophy is to automate my rig to simulate real human anatomy. The key to making automation work is to create layers of control, so you can make broad, complex movements on your character by moving or rotating a single control, but then give underlying control to the smaller parts as well, so you can precisely control the more individual parts of the character. Also, to go along with what Celshader said, it makes a lot of sense to tie multiple bones like forarm bones to a single control. Any time you can create less keyframes to accomplish the same goal, it makes it easier to manage when you have to go back later and adjust the timing or position of those keyframes.

4. I haven't found the need for anything other than Lightwave's expressions. As far as what kind of expressions to look into, start simple. try setting up a spine where the rotations of all the spine bones are controlled by the rotation of one null. Then, add a second null, and add the rotation of that null to just the upper part of the chest, to give additional control of the shoulders. Take it from there and see what happens.

Eric

Steve Warner
04-13-2005, 02:18 AM
First, let me say "Thank you" to everyone for your detailed replies. I consider riggers to be the miracle-workers of 3D. You take a cold hard mesh, weave your magic, and make it pliable in the hands of the animator. I have the greatest admiration and respect for your talents and skills. And I truly appreciate the wide range of replies you've all given. I know that there's no "one" way to rig, just as there is no "one" way to do anything in 3D. So the divergent advice is compelling to say the least. I've been digesting the information throughout the day and am trying to fit it into my limited understanding of rigging. I hope you won't mind me asking what may seem like obvious questions. My goal is not merely to rig a character, but rather to understand fully the rigging process. To be able to problem solve a rigging issue in the same manner that I can problem solve a modeling or texturing dilema. And my hope is that this dialogue will help enable that.

I find it interesting that most people say they use IK for the arms. I was always under the impression that IK was more of a leg thing. Still, the reasons given make great sense and I'm taking them to heart.

I'm posting a picture below that shows the current problem I'm having. When I talk about limits, I'm not really referring to the bend at the elbow (as I've already pre-bent that), but more specifically the clavical/shoulder area. I can prevent the type of horrible deformation I'm getting on the circled area below, but I have to set limits or just use FK in order to do so. My understanding has always been that limits were the sign of a bad rig, and your comments have pretty much confirmed that. So my next question is how do I avoid this? Is this the type of thing that expressions are used for? If so, why not just use limits? If expressions and limits aren't used to fix this, then should I be looking into a particular motion plugin? Possibly even a multi-goal IK chain in the clavical/shoulder region?

It seems from the details you've all given that expressions are used to cut down on the number of items which you need to keyframe. Is that their primary purpose in a rig? In that regard, would I be wrong to consider them as "simplifiers" or "shortcuts"?

Thanks again in advance for the time you're taking/ have taken to help me out. I truly appreciate it.

http://www.trinitymediainc.com/Help/Ouch.jpg

T4D
04-13-2005, 02:42 AM
ok to control the shoulder and the hold/deformation bone here's what i do

1/ create a null and with parent in place OFF parent it to the hold/deformation bone
2/ move the null long on the Z axis ( or whatever axis moves it along the bone ) so it's very close to the shoulder bones ( IMO you have one too many shoulder joint bones your over IK'ing that joint )
3/ with parent in Place ON re parent the Null to one of the shoulder joint bones
4/ Now target the hold/deformation bone to the null you just made and moved and they you go ( oh maybe rename it and then hide it, it's not a animation control. )

that hold/deformation bone will now follow the shoulder joint and there's one less things to key. and I also turn down the strength of that bone so it's a soft hold bone for that joint.

another thing I used to have IK controling the shoulder But now i don't, I prefer to key it manually now, I'm sure alot love IK on the area but I don't. and that bad shoulder pose your getting wouldn't be there if you had NO ik on the shoulder.

shoulder have to be key as you animate anyway so why have it control by IK at all ?
Shoulder give alot of emotion to the body when animating, even if it is targeted to a control of some sort the ik really not needed, I live by K,I,S,S when it comes to rigging:thumbsup:

ericsmith
04-13-2005, 04:16 AM
Hey Steve,

You actually make a good point about using limits in the shoulder area. My rigs have limits on the shoulder and upper bicep. The bicep (the joint at the end of the shoulder) should never go above horizontal, and the clavicle shouldn't go more than 20 degrees or so below horizontal. This is the way real human anatomy works. I also add some stiffness to the clavicle so it only moves when the arm pulls it, and I have a very short bone just before the clavicle that I can manually rotate to do things like shrugging the shoulders. In general, the one problem with using limits is that you can't ease into them, but in a dual bone limit setup like this, you'll never notice a problem with that.

Eric

Carm3D
04-13-2005, 04:21 AM
Here's an IK arm rig I created recently. Not all the clavicle / arm bones touch like in this one but it's just an example...

First get THIS (http://www.flay.com/GetDetail.cfm?ID=2047) plugin.. install it.. then load up my scene.

Then load up the scene file into LW.

How to use: in order for the expressions that twist the forearm to "see" the rotations happening in the wrist, you must first bake the bank channel of the hand after animating (there is a simple 50-frame animation in there ready to go).

After baking the forearm should twist properly.

Another noteworthy item is the upper arm.. I'm doing something very non-standard here methinks. The bone that shoots out of the arm socket only rotates on the heading and pitch. The second upper arm bone rotates on the bank (via IK) to point to the elbow IK null. This kinda sorta immitates the way the bicep and other mucles spin around the bone. It's not too accurate, but it's enough to slide by in most situations.

The advantage in doing it this way, I feel, is it creates less deformation issues where the arm joins the body.

Enjoy.

Steve Warner
04-14-2005, 07:21 PM
Thanks again for your help guys.



T4D: I followed the steps you outlined and as soon as I chose my Target Item in the motion properties panel, the hold/deform bone rotated to an obscure angle. I was able to get it back into the proper rotation, but it required my moving the null way out to the front and to the side. I then repeated the steps but instead of targeting, I set the Null as the a Goal Object, enabled Match Goal Orientation and set IK for Heading, Pitch, and Bank. That worked better and I like the automation that provides, but I think I'm going to have to set an expression to handle the bone size in order for it to fully work. Still, that was a nice tip. Thanks! As for not setting up IK on the shoulder but leaving it for the arm, I'll give that a shot. I'll also try eliminating one of the bones from the shoulder to see if that doesn't help. Thanks again!



Eric: Thanks for the extra info on the use of limits. That really helped clarify a few nagging questions I had and I appreciate your input. I also like the idea of putting in an extra bone for shoulder shrugs and will give that a try.



Carm3D: Thanks for the sample rig! It's very straightforward and seems like it gives great results. I like the multi-goal IK chain. I'm still a little confused as to why you're using the Match Goal Orientation plugin as opposed to the one that's built into LightWave. The plugin site said that its main purpose was for game developers so that they could bake out the rotation. But that doesn't seem to be what you're using it for. Can you give me more advice on that?



Okay, I hope you don't mind but I have more questions.



1. I understand that it's generally best to have IK only on one channel. And I understand that you can set up extra bones to handle other rotation channels. You'll notice from the above pic that I've got IK set to two channels on most of the clavical/shoulder bones. I did try a version where I had one bone for the Heading IK, then a small child shooting off (pointing down the Z) that handled the pitch, but the deformations I got from that approach weren't as good as when I just had IK set to two channels. So my question is this. What are the practical issues I'll run into by using IK on more than one channel? Is it a problem with flipping? Is it a problem with bad deformations?



2. Why is RPR bad? What will it do? I've used it to correct the pitch in several of these bones by (1) switching to Local Coordinate System, (2) using Bone Twist and (3) recording the Pivot Rotation (and of course switching back to Parent Coordinate mode). I've been searching through the posts here that deal with rigging, but I've yet to find one that explains why RPR is bad. I know it will affect targeting and expressions, but what exactly does it do? How will I recognize it when it happens? I know that Jonny says to avoid it, but Larry says to use it in the right places. What are the right places?



Thanks in advance for the help,



Steve

T4D
04-15-2005, 02:22 AM
Thanks again for your help guys.



T4D: I followed the steps you outlined and as soon as I chose my Target Item in the motion properties panel, the hold/deform bone rotated to an obscure angle. I was able to get it back into the proper rotation, but it required my moving the null way out to the front and to the side. I then repeated the steps but instead of targeting, I




Hmm that's odd :shrug:the idea behide it is the null copies prefectly the deformation bone position and rotation Because you parented with parent in place OFF you moved it only on the Z axis and when you turn targeting on the bone basicly targets a clone of itself so they shouldn't be any flip out rotations ?? you got me freaking out..
I'll do a video tutorials this weekend to explain the method I uses it for all sort of thing like auto toe bend ( when i want it ) shoulder deformation and all sort of auto bone animation



1. I understand that it's generally best to have IK only on one channel. And I understand that you can set up extra bones to handle other rotation channels. You'll notice from the above pic that I've got IK set to two channels on most of the clavical/shoulder bones. I did try a version where I had one bone for the Heading IK, then a small child shooting off (pointing down the Z) that handled the pitch, but the deformations I got from that approach weren't as good as when I just had IK set to two channels. So my question is this. What are the practical issues I'll run into by using IK on more than one channel? Is it a problem with flipping? Is it a problem with bad deformations?



2. Why is RPR bad? What will it do? I've used it to correct the pitch in several of these bones by (1) switching to Local Coordinate System, (2) using Bone Twist and (3) recording the Pivot Rotation (and of course switching back to Parent Coordinate mode). I've been searching through the posts here that deal with rigging, but I've yet to find one that explains why RPR is bad. I know it will affect targeting and expressions, but what exactly does it do? How will I recognize it when it happens? I know that Jonny says to avoid it, but Larry says to use it in the right places. What are the right places?

Steve

1/ you can have more then one channel control by IK but it's best to only have one
but I do have my upper in most characters with 2 channels control by IK THO as soon as i see a problem I split the bone make one of them extemely small and go back to 1 channel per bone method. ( that if I'm using IK for the Arms )

2/ RPR Layout doesn't save the changes as it should and other thing can't read the new rotation, when you reload a scene the bone have the old rotation setting even tho've done alot of work after that
YOu can open the bone option and reset the rest Position and get this working again But even after this, I've save the file then reloaded and and some not all the bones have gone back to pre RPR rotations :rolleyes:

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