|
[ Pobierz całość w formacie PDF ]
.A few years ago, we had to model a real-istic cheetah for a commercial.Not content with the stock footage welocated on the Internet, the animator went to the Bronx Zoo and videotapedan hour of cheetahs pacing and running through their compound.We thencaptured the best clips on an NLE system and imported the keyframes into3ds max.There the animator took the still frames and matched up the wire-frame model of the cheetah we built earlier.This produced authentic resultsand since then this has been our modus operandi for replicating nature.But the client hated the results! Although the cheetah was anatomicallyprecise (it even fooled a zoologist who came to see our work), the clientthought the cheetah looked stiff legged. Well, that s the way cheetahsreally walk. No, make it more fluid.Make it like a cat. So we got some catwalks on video and merged the two sets of points.The client liked that bet-ter but was still not completely satisfied.Apparently, the replication of reality is not always what people expect tosee in animation.What they really want is creative exaggeration.So wewent back to our cheetah/tabby cat and pushed and pulled the bones a bitthis way and a bit that way until it sort of slinked across the screen.Itslinked in a way that no real creature slinks.But guess what? Theclient loved it and after three months of fiddling (and waiting for our final 07_200505_Avg_ch07 9/5/03 11:34 AM Page 316Chapter 7316payment) we satisfied the client and rendered for the last time.It was anexaggeration of reality that the client wanted, not replication.So when you are faced with animating a character and you ve studied allthe Eadweard Muybridge2 photos, stock footage, and anatomical drawings,feel free to add a bit of your own personality to the project.That s when youelevate yourself from the level of mechanic to the level of artist.Function CurvesAfter you have test-rendered your character animation, the results mightnot be what you expected.My experience with novice animators (and not-so-novice clients and producers) is that any initial attempts to create smoothmovement using keyframes often result in unaesthetic cornering. In otherwords, you may want a smooth sweep of a hand from point A to point C, withthe midpoint at point B.Instead of a smooth continuous flow from A throughC, you get a noticeable effect at point B, which animators call a corner, because the most common application of three-point keyframes is a flyingobject, and when the object badly transitions through point B, it seems toturn a visible corner in space.Actually, this is a good thing, because it provesthat computers still aren t clever enough to think like humans (and the daythey are, all our jobs are toast).If you get results that don t look as smooth or as realistic as you d like,you will need to use the tools that control your keyframes.In 3dx max, theseare called function curves, in LightWave they re called motion graphs,and in Maya they are called graph editor animation curves.These functions all work basically the same.These graphical controlsenable you to view, often during playback, the actual characteristics of theanimation as they change over time.These controls appear as variousgraphed lines and curves.Therefore, if you see cornering in an animation,it will appear as a sharp point between two lines.2To win a bet, the governor of California hired Muybridge (1830 1904), a photographer, todevelop a means of photographing horses while in movement.Muybridge s sequential photosof a horse galloping won the governor s bet and Muybridge s fame.Today you can find his pub-lic domain sequences on the Internet.They are useful in animation motion studies of almostany animal, including humans. 07_200505_Avg_ch07 9/5/03 11:34 AM Page 317Rigging and Animating Characters317The function curve, motion graph, and animation curve tools enable youto modify the graphs with editable splines.Just as spline curves enable thecreation of smooth surfaces on a 3-D object, they also serve to providesmooth transitions between keyframes in an animation.By altering theshape and steepness of the curve, you can alter the appearance of your ani-mation.These functions therefore provide a valuable interactive feedbackmechanism you can use to tweak your animations to perfection. 07_200505_Avg_ch07 9/5/03 11:34 AM Page 318 08_200505_Avg_Index 9/5/03 3:20 PM Page 319INDEXNote: Boldface numbers indicate illustrations
[ Pobierz całość w formacie PDF ]
zanotowane.pldoc.pisz.plpdf.pisz.plhanula1950.keep.pl
|