View Full Version : doubt about game char rig
12 December 2008, 12:34 PM
Is there any difference between Game character rigging and movie character rigging?
If Yes, Please let me know.
12 December 2008, 01:48 PM
i had the same queries about a year ago, then i landed a job rigging in games so i think i can clear some stuff up for you. btw i use Maya so if my terminology is maya oriented, and you don't use Maya apologies :)
basically the principles are the same but games are more restricted in what you can use to create the deformations you require. basically we use joints for everything as the engine can build joints cheaply (sometimes we use blendshapes (morph targets) but in some of our engines were limited n the number we can use, and how many can be used simultaneously, so we avoid these if we can). but unless the programmers have coded in support an particular deformer, or setup an in game real time deformer, you cant use things like lattices, clusters, wraps, dynamics.... ect
so for instance if you need a dynamically jiggling thing youll need to constrain some joints to it to deform the mesh (pretty simple), where as in feature rigs your free to deform the mesh directly as the output is just the rendered mesh. also if your setting up this dynamic object to be animated in your app (Maya , max, xsi...whatever) you'll need to give the animator the abililty to bake the animation out. so it can be set to a exact position so it will match if blended with another animation
also one of the main things we do is keep the joint hierarchy separate and clean, as in a joint can only be parented to another joint (not a group under another joint with an offset position)
also one other thing (that causes some debate in my place of work :) ) is that the fact that, in games, you are limited to joints and usually by the joint count. so you will have to position your joints slightly differently. by this i mean if you were building a feature rig with a full muscle system you can be as anatomically correct with your joints as you want as you know the mass and volume should be simulated pretty realistically, but if you need to use one joint to control the whole area of, lets say, the shoulder/clavicle then if you place that anatomically in the right place you'll get some nasty rotations on the back of the skinned clavicle as you rotate it forward as it will be too far forward. so you'll need to play about and test :).
well that's how Ive found it although there are some people who stick to anatomy, but when it boils down to it all if it deforms better that's the right position.
oh and also we've had to, in the past, rig joints with he scales inline with he world as some engines cant handle non uniform scaling. so for that we had to use the rotate axis to orient joints as that leaves the scale (think this is calculated after the scales in the matrix multiplication). which can seriously hamper any stretchy joints or other cool rigging techniques. we then have to 'fake' it with translations of another skinned joint.
hope that helps.
12 December 2008, 04:31 PM
The key difference is this:
A game rig has to last the course of the game. A film rig only needs to last the length of the shot. I.e you can make rigs in film that only need to work in one angle/shot but for games generally the rig has to work in and from every direction/shot.
Other differences, muscles, deformation are getting smaller and smaller every day - the Crysis rigs are getting pretty close to film rigs in terms of technology.
12 December 2008, 10:11 PM
There are two Key Differences.
Game Rigs need to have the correct Transform information in the animation.
Parent Constraints directly to the In Game Skeleton will not give you the right transforms.
Take for example: 1 bone skinning 1 cube. The Bone is parent constrained to a Nurbs Circle. When you animate it, none of the transforms the circle goes through will translate to the bone. The bone will only have the animation data relative to the parent.
Now, if you take the same setup, but instead of a Parent constrain, you use Point and Orient Constrains. Then everything will come through. Any animation applied to the Nurbs Circle will applied to the bone.
Vertex Animation, For the most part, Blendshapes are as far as Game Engines go. Everything has to consist of Bones and/or Blendshapes. There are of course ways around it.
one Minor thing that you won't hear much about is Vertex Influences. Games have to run smoothly, so often the Vertex Influence is limited to 3 or 4 bones.
All in all, You can't cheat as much with a Game Rig. The Film Industry has it easy compared to the technical headaches of game rigging. But I do suppose they demand higher quality as a result.
12 December 2008, 08:23 AM
Might wanna checkout a new DVD I saw for sale at http://eat3d.com/training_videos/facial_rigging. It's about next-gen rigging.
12 December 2008, 04:07 AM
Thanks for your valuable replies Andylt, Eek, Brighton and BlackHwk.
Now I've some awareness on this. Thanks a lot.
12 December 2008, 11:42 PM
The best advice i can give is to keep your animation rig separate from the bound skeletal hierarchy.
If you add nulls, locators and other objects into skeletal hierarchy it will cause crashes and major problems in the engine.
The bones should be a single hierarchy, in film you can do some really cool broken hierarchy rigs, but in a real time engine, you will just get a broken character ;)
One last thing, depending on how many characters you need to be rendered at one time will determine how many bones you can use. Anything over 70 or 75 (I forget which it is) in some engines will have to render a second pass (killing optimization)
12 December 2008, 11:42 PM
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