Computer Animation

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Computer Animation

• 451-113 Introduction to Computer Graphics and
  Systems

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Principles of Animation

• The real world is continuous and analogue
• We perceive movement through changing scale and
  differential parallax
• In order to reproduce this we need to sample
  the real world, and to exploit properties of the
  human viewing system

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The Human Eye

• Our retina retains a latent image for about 1/15
  second
• If we can view a series of images faster than
  this, we will perceive this as fluid movement
• A lesser frequency (or frame rate) and will will
  see this as jerky

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Background

• Humankind has used illustrations and movement to
  explain stories for millennia
• shadows on cave walls
• wayang puppets
• lines in the sand

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The Industrial Revolution

• Science and technology facilitated the
  reproduction of movement
• Before photography, artists drew sequences of
  images and we observed then through a device to
  simulate movement
• After the 1830s, photography took over this role
  from artists

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Edweard Muybridge

• Often credited with being the inventor of motion
  pictures
• Studied the gait of humans and animals using a
  camera and a moving stage

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Movie Animation

• Walt Disney set the standard for cartoon
  animation of characters, Steamboat Willie
  released in 1928
• Once again artists drew key frames, and cheaper
  labour filled in the missing frames
  (inbetweening, a term we still use)

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Information Revolution

• Mechanical and manual methods of animation are
  replaced by computer systems
• Computer graphics packages are now used to create
  rendered frames, artists still supply creative
  input

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Animation Methods

• Animated GIFs
• Flythoughs
• Keyframes
• Parametric
• Motion Capture

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Animated GIFs

• Basically the same approach as a flip book
• A series of GIF images are played sequentially
• The basis of Web animation
• small, fast

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Software Systems

• MicroStation permits flythroughs and keyframing,
  with some script control
• Better systems use all methods
• It is a very involved process if it is to appear
  realistic

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Flythrough Animation

• For a flythrough, only the camera is moved
• All other elements remain stationery, including
  the objects, lighting, materials and so on
• Generally, a camera path is determined, the
  number of frames decided, and the rendering
  method set

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Keyframe Animation

• In this case the key frames are determined
• this includes materials, lights, objects, camera
  position
• The number of frames between the keyframes are
  determined
• The system then generated the in between frames
  (inbetweening!)

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Parametric Animation

• A set of behaviours are determined for each
  object to be animated
• These are then used to generate the animations
• Good for repeated sequences
• a flock of birds, water, rain drops
• often achieved by the use of plugins (3DMax)

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Some Examples
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Some Examples
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Live Action - Virtual Set
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Video Systems

• There are 3 common video systems used in the
  world, SECAN, NTSC and PAL
• In Australia we use PAL
• 760x576 resolution, 25 frames per second
• We need to use this if our animations are written
  to video tape
• If not, anything goes!

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Video (animation) Editing Software
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Codecs

• Short for compressors/decompressors
• Used to reduce the final file size
• full frame video at 25Hz 30Mb/s!
• very few graphics cards can reproduce this
• the Internet certainly cannot
• Common ones include MicroSoft Video (for AVI),
  MPEG, Quicktime, Real Video...

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Web Delivery

• Prerecorded video can be delivered across the
  Internet only if it is compressed
• Streaming is possible with some formats but not
  with MPEG
• Another approach to deliver animation is to
  produce VRML files
• gives interactivity and movement

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Virtual Reality Modelling Language (VRML)

• Delivers 3d geometry over the Internet, as well
  as animations
• Gives the user a degree of interactivity
• Support in the industry varies
• SGI Cosmoplayer now defunct
• Cortona VRML a new release
• see example

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Summary

• Good computer animation is difficult
• However modern computers give people a viable
  outlet for their creative bent
• A flythrough of a block of cheese is just the
  beginning!