Considerations for vertex weighting (initial pose?)
by soy.bean · in Artist Corner · 08/09/2003 (11:39 am) · 10 replies
I see that most game 3d modeller nowadays implement a continuous mesh on organic characters instead of segmentation ones. I know how wonderful the character animations would be on a continuous mesh and how they seem more 'realistic' than if it were segmented. It all depends on the vertex weighting process, which I know about, but what I don't know (and would like to know) is..
1. what's the initial pose for a good character vertex weighting? I used to make characters with their arms spread apart so it looks like a 'T' shape, but when I VW-ing them, sometimes the shoulder part would look annoyingly awkward if I have both arms down. I've seen other models where their initial pose would have the arms spread approx. 45 degrees from its torso, and some have both arms down. Now this triggers my second question..
2. Does the initial pose relate to how you want the character to be animated, or if I was really good at VW-ing, I would have any character initial pose put out and it would still have fantastic animations? What I'm trying to say here is that I initially thought that the 'T' shape for the character would give a great possibility for me to have it's arms both up and down (without any weird joint bending) if I have the VWs done nicely. But as I try that, it's not that easy as I thought it would be. I even think it's rather impossible (you'd always get some awkward joints somewhere). Well, then I saw the RW player where its initial pose had the arms down. If I try to pull up its arms, the shoulder joint got messed up (it twisted), but I also notice that the animations did not apply such actions. Then I remembered Sam Fischer (or Fisher?) from Splinter Cell. I think it's a continuous mesh but it seems like it doesn't have any joint flaws to it. It always looks perfect!.. how come?
Sorry if there happens to be another thread similar to this one. If there is one, just point me out an url and I'll shut up :):)
[g]
1. what's the initial pose for a good character vertex weighting? I used to make characters with their arms spread apart so it looks like a 'T' shape, but when I VW-ing them, sometimes the shoulder part would look annoyingly awkward if I have both arms down. I've seen other models where their initial pose would have the arms spread approx. 45 degrees from its torso, and some have both arms down. Now this triggers my second question..
2. Does the initial pose relate to how you want the character to be animated, or if I was really good at VW-ing, I would have any character initial pose put out and it would still have fantastic animations? What I'm trying to say here is that I initially thought that the 'T' shape for the character would give a great possibility for me to have it's arms both up and down (without any weird joint bending) if I have the VWs done nicely. But as I try that, it's not that easy as I thought it would be. I even think it's rather impossible (you'd always get some awkward joints somewhere). Well, then I saw the RW player where its initial pose had the arms down. If I try to pull up its arms, the shoulder joint got messed up (it twisted), but I also notice that the animations did not apply such actions. Then I remembered Sam Fischer (or Fisher?) from Splinter Cell. I think it's a continuous mesh but it seems like it doesn't have any joint flaws to it. It always looks perfect!.. how come?
Sorry if there happens to be another thread similar to this one. If there is one, just point me out an url and I'll shut up :):)
[g]
#2
The benefit of using a T pose is the arms are outstretched at 90 degrees, which makes rigging and vertex weighting on the arms much easier. However, a common mistake with this pose is people forget the shoulder area. You need to make sure the mesh parts that correspond with the deltoid and trapezius muscles are raised up when the arms are up at 90 degrees from the torso. With a normal human body, raisng the arms also raises all of the muscles in the shoulder area. Also, the rig (bones, biped, whatever) needs to have both the clavicle and shoulder joints raised slightly as well. Moving the arms up and down involves more than rotating the shoulder joint.
The alternate poses -- having the arms raised about 45 degrees from the torso or pointing straight down -- provide a more neutral resting position for the shoulders, which makes editing the vertex weights a bit easier. However, rigging and weighting the arms is less convenient, because it can be awkward setting up arm rigs at 45 degree angles, or, if the arms are pointing down, the skin envelopes in the arms and torso overlap. But, for many FPS-style characters, these poses makes more sense, because those charaters rarely raise their arms above their heads.
In my experience, neither way (arms up or arms down) is really better than the other. Just pick one and run with it. :)
08/09/2003 (12:30 pm)
There is no true right or wrong pose to use for your character. A lot of it depends on what your character need to do and on personal preference. It also depends on how the rig is setup and how well you edit your vertex weights.The benefit of using a T pose is the arms are outstretched at 90 degrees, which makes rigging and vertex weighting on the arms much easier. However, a common mistake with this pose is people forget the shoulder area. You need to make sure the mesh parts that correspond with the deltoid and trapezius muscles are raised up when the arms are up at 90 degrees from the torso. With a normal human body, raisng the arms also raises all of the muscles in the shoulder area. Also, the rig (bones, biped, whatever) needs to have both the clavicle and shoulder joints raised slightly as well. Moving the arms up and down involves more than rotating the shoulder joint.
The alternate poses -- having the arms raised about 45 degrees from the torso or pointing straight down -- provide a more neutral resting position for the shoulders, which makes editing the vertex weights a bit easier. However, rigging and weighting the arms is less convenient, because it can be awkward setting up arm rigs at 45 degree angles, or, if the arms are pointing down, the skin envelopes in the arms and torso overlap. But, for many FPS-style characters, these poses makes more sense, because those charaters rarely raise their arms above their heads.
In my experience, neither way (arms up or arms down) is really better than the other. Just pick one and run with it. :)
#3
08/09/2003 (1:20 pm)
I am starting to prefer this pose. Harder to rig and weight, but better deformation. I also like the hand back tilt, again, better deformation for the normal hand poses one finds.
#4
@Danny: thanks for the thorough explanation there. I got the idea now. It kinda reminds me that I wont be doing a Sam Fisher character anyway so I'm back with the "practice makes perfect" spirit :). Oh, one thing, I think that having something like a 'motion capture' reference sounds good for people like me who isn't very much experienced in animation. I mean, I kept on rotating the shoulder joint to see how it deforms and never thought that other parts needed to be moved for weighting considerations. Is such database exist for download/purchase?
@Joe: whooo.. nice model there. I wonder, do you plan to have her arms lift up? it seems hard to accomodate the deformation there. I see that you applied certain edge loops there (from the back of her ears to her breasts). I never thought in using edge loops in my model (hence, it's rather 'clean' and grid-like..:)) although I heard that it is very useful during animation cause it mimics how normal muscles are placed. Do you use some sort of reference to do them loops or just rely on your native artistic instinct?
thanks a lot guys,
[g]
(EDIT: forgot something :))
08/10/2003 (9:36 am)
@Patrick: a physique to skin converter? that sounds interesting, where can I find that?@Danny: thanks for the thorough explanation there. I got the idea now. It kinda reminds me that I wont be doing a Sam Fisher character anyway so I'm back with the "practice makes perfect" spirit :). Oh, one thing, I think that having something like a 'motion capture' reference sounds good for people like me who isn't very much experienced in animation. I mean, I kept on rotating the shoulder joint to see how it deforms and never thought that other parts needed to be moved for weighting considerations. Is such database exist for download/purchase?
@Joe: whooo.. nice model there. I wonder, do you plan to have her arms lift up? it seems hard to accomodate the deformation there. I see that you applied certain edge loops there (from the back of her ears to her breasts). I never thought in using edge loops in my model (hence, it's rather 'clean' and grid-like..:)) although I heard that it is very useful during animation cause it mimics how normal muscles are placed. Do you use some sort of reference to do them loops or just rely on your native artistic instinct?
thanks a lot guys,
[g]
(EDIT: forgot something :))
#5
I found this in the faqs here on this site.
08/10/2003 (11:13 am)
Http://sparks.discreet.com/downloads/downloadshome.cfm?f=2&wf_id=58I found this in the faqs here on this site.
#6
She will have her arms in the normal FPS 'gun hold' position, so I don't forsee that many problems, and, as you have noticed, the edge loopp placement helps with the deforamtion looking more natural. I started getting serious about mesh structure a few years ago after reading an article by Bay Rait on the subject of edge loops. I also have a bunch of books on anatomy. I have been using the Bridgeman books that define the planes of the body as a guide in my low-poly character modeling.
08/10/2003 (12:07 pm)
@GunturShe will have her arms in the normal FPS 'gun hold' position, so I don't forsee that many problems, and, as you have noticed, the edge loopp placement helps with the deforamtion looking more natural. I started getting serious about mesh structure a few years ago after reading an article by Bay Rait on the subject of edge loops. I also have a bunch of books on anatomy. I have been using the Bridgeman books that define the planes of the body as a guide in my low-poly character modeling.
#7
Most books on human anatomy will help in determining which bones move with which muscles (and vice versa). The Bridgman books are really good as is Christopher Hart's "Human Anatomy Made Amazingly Easy". Sounds like a cheesy book, but the information in it is really good.
As far as mocap references go, you might want to do a search on free data files in FBX format. I recall there being some database out there containing free mocap data.
08/10/2003 (12:53 pm)
@Guntur:Most books on human anatomy will help in determining which bones move with which muscles (and vice versa). The Bridgman books are really good as is Christopher Hart's "Human Anatomy Made Amazingly Easy". Sounds like a cheesy book, but the information in it is really good.
As far as mocap references go, you might want to do a search on free data files in FBX format. I recall there being some database out there containing free mocap data.
#8
@Danny: Man, you guys are lucky. I couldn't find those particular books you mention here in my country. well, not in my local bookstore for sure. I'll prob have to go to Jakarta or worst yet, to Singapore to get such books. I'll have that in my list though. Bridgman and Christopher Hart. thanks :)
So I guess, animators like you would have to mocap yourself huh? Won't it cost you? the time and well, money?
[g]
08/11/2003 (11:14 am)
@Joe: Yes, Bay Rait!! I wanted to mention him in my post but forgot his whole name.. Bait something as I try to recall heheh.. Yeah, he had me hooked on poly modelling in the first place.. but well, had college to do (which then I felt it was a mistake, chose the wrong major, erm.. anyways) so I hadn't the much time to really focus on 3D modelling :(. till now, that is :).@Danny: Man, you guys are lucky. I couldn't find those particular books you mention here in my country. well, not in my local bookstore for sure. I'll prob have to go to Jakarta or worst yet, to Singapore to get such books. I'll have that in my list though. Bridgman and Christopher Hart. thanks :)
So I guess, animators like you would have to mocap yourself huh? Won't it cost you? the time and well, money?
[g]
#9
08/11/2003 (11:59 am)
I almost always animate my characters by hand. I only use mocap data if the project calls for it.
#10
08/11/2003 (12:06 pm)
Motion Captre is a tool of the devil! Seriously though. I also animate my stuff by hand unless the project calls for motion capture to be used. For mocap at reasonable prices... check out this guy troymcfarland.com/ 
Torque Owner Patrick Glaspey
Also skin modifier is not as good as physique. There is a utility to convert a physique skinning to a skin modifier which I have not tried yet but plan to on my next rev of the models I am working on.
There is a good book by Paul Steed called Animating Real Time Game Characters that has a pretty good section on setting up the rig and weighting methods for biped and physique.