Key Frame Animation Amy Gooch AA3: Intro to Animation
3D Animation Rendering • 3D Scene and Motion • Sequence of Frames • Rates: Video 30fps, Film 24fps • Persistence of Vision Animator must create .. • Illusion of Life • Weight
Animation • Almost every property of every object in the scene can be animated (changed through time) • Models, cameras, … • Transformations: • Move • Rotate • Scale • Modifications/Deformation: edits, bends, twists, manipulating a skeleton • materials, colors, textures
Animation • 3D Scene does not have • Gravity • Weight • Force • interactions between objects • (bit of a lie) • You must make it seem so!
Primary methods of Animation • Keyframe • Procedural • Expressions • Scripting • Dynamics/Simulation • Physics • Motion Capture • Combinations of the above
Keyframe Workflow • Set Keys • Usually extreme positions • Less is more: Keys only the properties being animated • Set Interpolation • Specify how to get from one key to another. • Secondary, but a necessary step. • Scrub Time slider and refine motion curve
Setting Keys • Start with extreme positions • Add intermediate positions • Secondary motion • Less is more • Don’t add keys for properties that you are not animating • Easier to manage/edit fewer keys
Motion Curves Is the box • Starting from stop or at rest? • Stopping at the end or continuing? When is the box going • Forward? • Backward? • Fastest?
Interpolation • Specify how to get from one key to the other (inbetweening) • Common types • Step: stay at the same value, then suddenly switch • Linear: change at constant rate • Spline/Smooth: make it smooth • All of these (and more) are useful and appropriate in the right circumstance
Smooth Interpolation Soft changes of direction
Linear Interpolation Hard changes of direction Appears to be contacting other objects, instant changes
Step Interpolation Object reappears in a totally different position This is very useful. When?
Ease In/Out • Heavy objects take a while to get going • trains • Use interpolation to emphasize this. • Ease in/out –or- Slow in/out means to leave the key slowly
Timing of the action • Ahead of the story • Something will happened before we know what it is • audience not yet aware • character may knows what’s up • Ex Alien Song • Behind the story • Audience knows before character knows • Ex: KnickKnack (1989) • Keep audience Interested!
In class: bouncing balls • Grab file: http://www.cs.northwestern.edu/~animation/Balls.mb • Each person will spend 10 minutes making one type of ball bounce • Then in turn, each group member will tweak the animation
Resources • Laws of Cartoon Physics • http://www.cc.gatech.edu/classes/cs8113f_97_spring/cartoon.html • Learning Maya Tutorial list • http://www.learning-maya.com/rigging.php • Skeleton Tutorial • http://web.alfredstate.edu/ciat/tutorials/SkeletonSetup.htm • Rag Doll; Skeleton by Proxy tutorial • http://www.goldenxp.com/tutorials/ragdoll/ragdoll1.htm • 5-minute Leg Rig • http://www.noir.org/tutorials/Xen%20Wildman/legrig/legrigtut.html
Credits • Winny • Jessica Hodgins • http://www.cs.dartmouth.edu/~brd/Teaching/Animation/animation.html