   Facial animation idea
  The articles I''ve seen on emotional facial animation seem to focus on a system of bones, and I just now accidentally thought of an alternative method which uses muscles. Please tell me what you think (or if it''s already been done)A few rigid bones are ised for the jaw but the skin patches are linked to a network of light elastic springs which hang closely to the bones at fixed lengths in a relaxed pose.Say you want to have a frame of animation for a ceryan visceme (sp?). You move the muscle nodes to the appropiate positions and then calculate for each spring muscle the coefficient of elasticity needed to maintain equilibrium (as a multiple of the relaxed state coefficient). Resolving components should just boil down to simultaneous equations.Animation is done by changing the coefficients of elasticity!As one muscle tightens and another relaxes, the skin should simply morph gradually to the next position.Now, emotion! I''m a little unclear on how the bones systems do it but with my method all you have to do is creatre another frame of animation for "big grin" or whatever and multiply the elasticity scaling factor with the one from the visceme animation.Example: Say we have a node at the corner of the mouth. For big grin the muscle above it has it''s elasticity multiplied by 1.2 to pull it up a bit. For the "ah" visceme the same muscle has a coefficient of 0.85. For saying "ah" while grinning that muscle has a coefficient of 1.02. The effect will be a little distorted by the surrounding muscles.The key to it is you can overlay and interpolate as many expressions as you like and it should still find a sensible shape. This means you could have someone tonguing their back teeth to dig out a raspberry seed and it would shift the jaw, and laugh at the same time.You could add physical modelling to the whole skin. Say a fat man with flabby cheeks turns his head rapidly, his skin can have intertia!   ********I am not the Iraqi information minister.GSACP  : GameDev Society Against Crap PostingTo join: Put these lines in your signature and don''t post crap! 
  is your graphics card good enough to run NVidia''s dusk demo?quite nice for face expressions... uses bones btw.. and lets you play with the expressions with some kind of sliders really nice.. if you can, have a look at it (requires a GeForce FX 5900 ultra btw...)but there still is a video on the demo page, but you don''t see the guy playing around with those sliders if I remember correctly anyway, your method seems quite interesting... but is it efficient enough to be real time? (is it _meant_ to be real time at the first place? :D)and you can do all that with bones as well... I don''t see what you can''t do with bones but can do with your method? ;  Check out the Shrek DVD.If you haven''t got it (shame on you) go and buy it.Anyway, they show/describe/talk about the system they used for developing the movie.  It uses a skeletal body, which then has the muscles attached to it (realistically I might add - for an ogre and a dragon that is ), then skin onto the muscles.  Clothing and hair went onto that.  Each hair was seperate on some of the characters I might add, as were the leaves and the grass.They also show the way they did the fire, and show the models/animations of Princess BEFORE they made her more cartoonish, as she looked too realistic.For other stuff, they showed the computers they used to make them on (one had a train set on it, and another was decorated like a tropical island) and they explained how they used all the computers at their disposal to render the movie whilst they were not being used (around the building etc).This is on the retail version  of the Region 4 DVD anyway.  Should be on the other ones aswell.  I''m not sure if its on the rental version either.  Probably is.  Don''t think they make them too different. ;  Yeah, the girl goes on her knees and then the guys cums on her face. How much harder can it get? ;quote:Original post by sBibi  but is it efficient enough to be real time? (is it _meant_ to be real time at the first place?Of course, the calculations done at runtime are just a set of linear interpolations for the muscle strengths and then it''s no more expensive than cloth animation.I didn''t know they used bones/muscles/skin for shrek, I thought these things were largely done by hand and patch control points. ********I am not the Iraqi information minister.GSACP  : GameDev Society Against Crap PostingTo join: Put these lines in your signature and don''t post crap! ;  The Half-Life 2 engine uses that system if I''m not mistaken. There''s some information about it (especially the eyes) at http://www.gamespy.com/previews/may03/halflife2pc/index2.shtml (see : "The eyes have it", on the bottom of the page). 