Gurbo Posted June 7, 2005 Share Posted June 7, 2005 Pretty straight forward question, I've found I can't assume anything in Houdini will be the same as Max or Maya. Is it best to rig characters in Houdini with pre-bent limbs so the IK bends the joint in the right direction? Also I notice that Valerie puts together a IK chain of three bones in the SideFX rigging video (a Bicep, a little one in the elbow and the fore-arm bone). This was considered a taboo in Max. Tar Gurbo Quote Link to comment Share on other sites More sharing options...
michael Posted June 7, 2005 Share Posted June 7, 2005 I'm not sure why Valerie put in the extra bone - she mentions something about it but I can't remember what...anyway, I wouldn't do it... as for being 'pre-bent' it's a good idea... although you can make your chains straight and give them a 'hint' about what the prefered directions is...once again I can't remember where I read/heard that...I think it's in the User Guide... ...least helpful post ever... Quote Link to comment Share on other sites More sharing options...
peship Posted June 7, 2005 Share Posted June 7, 2005 Ok if you just want to properly orient the bending of your IK chain then you dont need to align the bones under some angle before applying the IK CHOP. You need only to set the rest angles of the joints, they determine in which direction will bend the joints later. Actually there is an important reason why your limb joints should be aligned on some small angle. When you strighten-up the IK chain in animation there is some poping effect. I think most of the animators really hate that. This angle offeset halps them to preserve the poping and to make the animation more natural. I think most people cant notice the problem explained above, but if you deal with some high-quality animation projects you must pay it attention. Quote Link to comment Share on other sites More sharing options...
michael Posted June 7, 2005 Share Posted June 7, 2005 hahahahahahahahahaha... animators don't care about anything, they just animate away and leave it to others to find/fix the problems... (I'm not bitter, really) setting an angle will not prevent the arm(leg, whatever) from hyperextending and poping back...unless you use limits (which animators hate)... Quote Link to comment Share on other sites More sharing options...
thekenny Posted June 7, 2005 Share Posted June 7, 2005 Yes you are bitter. Just slightly;) actually Val put the extra bone in there to help out the deformations in the elbow region, I believe. I've seen people do this in the sockets for shoulders and hips as well, just to get a better range of motion. It gives you more to weight to as well. Does it help... maybe? -k Quote Link to comment Share on other sites More sharing options...
michael Posted June 7, 2005 Share Posted June 7, 2005 yeah you're right it is there to help weighting/deformation...but I doub't that her model really needed it....I'd prefer to capture as few bones as possible first - then rough weighting...which will show you where you could use the extra help - then you have 100% control over any new bone you introduce (placement/animation, capture, weighting etc). Quote Link to comment Share on other sites More sharing options...
peship Posted June 7, 2005 Share Posted June 7, 2005 animators don't care about anything, they just animate away and leave it to others to find/fix the problems... (I'm not bitter, really) i agree with you - the animators dont care about that, but the animation directors care ( at least the good ones ) and they are kicking butts and animators are crying on our shoulder and we are giving them few degrees of freedom more, just to calm them down a bit. setting an angle will not prevent the arm(leg, whatever) from hyperextending and poping back...unless you use limits (which animators hate)... 18612[/snapback] In most cases the modelers should bring character geometry with stright aligned limbs. If we capture this geometry to stright aligned joint chains then in animation, when the animators strighten the IK chain the deformation of the limb will look right and the poping will appear. This effect is difficult to catch because it is almost invisible and difficult to fix shot by shot. But if the riggers are binding the geometry to joint chains wich have small angle then in animation, if the animator strighten the chain the deformations will look weird ( the limb will bend in opposite direction ) and this will force the animator to put some extra efforts to prevent the strightening of the chain. Quote Link to comment Share on other sites More sharing options...
michael Posted June 7, 2005 Share Posted June 7, 2005 this will force the animator to put some extra efforts to prevent the straightening of the chain those, unfortunately, are the magic words.... I've never seen a model come into rigging with straight limbs, they are always slightly bent, so the default position for the bones will also be slightly bent... but nothing short of built-in limits will prevent animators from straightening out limbs - or animation directors from asking for poses that force the animators to do just that... Quote Link to comment Share on other sites More sharing options...
Jason Posted June 7, 2005 Share Posted June 7, 2005 A quick question for Arctor - have you seen people use the IK Dampening (on the InverseKin CHOP) much? Quote Link to comment Share on other sites More sharing options...
michael Posted June 7, 2005 Share Posted June 7, 2005 never... I think it's a great idea - the studio I worked for in calgary had a cool maya plugin that would optionally turn rig proxy geometery red as you approached the 'limits' of the rig - just as a warning... but again it's a limit that animators will always want to turn off "just for this one shot"...they will plead...and then all hell will break loose... I'd like to use it (IK damping) personally but doubt that anyone else would.... Quote Link to comment Share on other sites More sharing options...
Gurbo Posted June 8, 2005 Author Share Posted June 8, 2005 but again it's a limit that animators will always want to turn off "just for this one shot"...they will plead...and then all hell will break loose... 18630[/snapback] This is the only place where I've read about someone paying out on animators. I'm coming from a 2D animation background and to get more 'bang for your buck' it is suggested that the animator 'break' the joints. Momentarily crack the knee backwards as your character puts their foot down to get a cartoony motion. Richard Williams advocates this quite a bit in his book. As far as 3d stuff goes I find this technique really hard to pull off in terms of rigging. Is it best just to not bother and accept this as a limitation of CGI character animation? Gurbo Quote Link to comment Share on other sites More sharing options...
peship Posted June 8, 2005 Share Posted June 8, 2005 As far as 3d stuff goes I find this technique really hard to pull off in terms of rigging. Is it best just to not bother and accept this as a limitation of CGI character animation? do you think mr. Incredible would look so nice if the guys at P dont care ? Quote Link to comment Share on other sites More sharing options...
michael Posted June 8, 2005 Share Posted June 8, 2005 "...paying out..." never heard that expression before...but I think I understand it it really all comes down to what style of animation is used... it's possible to build a rig with or without swash and stretch, with or without 'breakable' joints, with or without 'limits' etc etc....depending on the needs of the show... the real problems only come when rigs are asked to do something that they are not designed for - sometimes this is simply something that was not forseen but often it is an animator choosing to achieve a pose/movement in a way that the rig cannot accommodate - so it's either fixed later or some kind of workaround is found between the various departmants... to peship > it's not about caring at all...everyone wants to do the best job they can but everyone also has the pressures of getting the job done on time and on budget so compromises have to be made... Quote Link to comment Share on other sites More sharing options...
thekenny Posted June 9, 2005 Share Posted June 9, 2005 I can't remember exactly but the IK dampening had a problem.. I think it was a combination of it couldn't do it and something else.. noK maybe? We tried it early on for complicated shoulder hook ups form quadraped legs, but went away from it. Maybe the E.D.W.A.R.D. will read this thread and remember what it was... As far as straight limbs for weighting/binding.. I would recommend a dead man pose. Everything slightly in the middle position for everything, eyes, jaw, arms, legs. It makes rigging and weighting easier, but you have to provide animation with an animation ready pose so the character always is starting in "realistic" manner. -k Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.