Animation. CS334 Fall Daniel G. Aliaga Department of Computer Science Purdue University

Transcription

1 Animation CS334 Fall 2013 Daniel G. Aliaga Department of Computer Science Purdue University (Slides based mostly on those of Arjan Egges and Timothy Chan )

2 Introduction Animate = Give life to Adding the dimension of time to graphics Animator specifies movement of objects through time and space

3 Two main categories Computer-assisted animation 2D & 2.5D In betweening Computer generated animation Low level techniques Precisely specifying motion High level techniques Describe general motion behavior

4 Introduction Low-level techniques Shape interpolation Helps the animator fill in the details of the motion given enough information Animator has a fairly specific idea of target motion High-level techniques Generate a motion given a set of rules or constraints Object motion is controlled by a model/algorithm Fairly sophisticated computation, such as physically-based motion

5 Perception Eye/brain assembles images and interprets them as continuous movement Persistence of vision: sequence of still images shown at a fast enough rate to induce sensation of continuous imagery Eye retains visual imprint once stimulus is removed positive afterimages Persistence of vision is not persistence of motion

6 Perception Persistence of vision lower bound: Playback rate of images Critical flicker frequency Persistence of motion has an upper bound: Object moves too quickly Motion blur Two important rates: Playback/refresh rate Sampling/update rate

7 Typical Playback Rates Film Imax NTSC TV PAL TV HDTV Computer 24 fps 48 fps 30 fps (interlaced) 25 fps (interlaced) 60 fps ~60 fps

8 Animation History: The early days Persistence of vision: discovered in the 1800s. Zoetrope [video] Flipbook Thaumatrope [video]

9 The early days End of the 19 th century introduced moving image by using a projector. Magic Lantern and shadow puppets

10 The early days Zoopraxiscope (zoetrope + projector)

11 The early days Kinetograph/kinetoscope First motion picture camera/viewer

12 The early days Animation movie pioneers J. Stuart Blackton (smoke effect, 1900) First animated cartoon in 1906 Used a chalkboard for drawing and erasing frames Emile Cohl (Fantasmogorie, 1908) Winsor McCay (Little Nemo) Each image redrawn on rice paper and then filmed

13 The early days Major technical developments by John Bray (1910): compositing multiple layers of drawings into a final image (celluloid) using grayscale Drawing background on long sheet of paper for panning Max Fleischer patented rotoscoping in 1915

14 The early days First animated character: Felix the Cat (Otto Messmer) in early 1920s. Disney came around end 1920s, introducing a number of innovations Storyboards Pencil sketches for reviewing motion Multiplane camera Using sound & color

15 Multiplane Camera Move scene layers independently of camera Six directions of movement for each plane

16 Multiplane camera Powerful tool: More effective zoom Move foreground image to the side Parallax effect Moving planes at different rates Adding depth cues Blur the images on more distant planes Introduce motion blur by fast moving planes

17 The early days Sound was added for the first time in Steamboat Willie (1928) Disney promoted idea that mind of the character was the driving force of the action Analysis of real-life motion

18 MGM and Warner Brothers, etc.

19 Other Media Animation Computer animation is often compared to stop motion animation Puppet animation Willis O Brian (King Kong) Ray Harryhausen (Might Joe Young, Jason and the Argonauts)

20 Other Media Animation Claymation Sand animation Physical object is manipulated, image captured, repeat

21 Production of Animation Preliminary story Story board Detailed story Key Frames Test shot Pencil test Inbetweening Inking Coloring

22 Pioneering animation movies Pixar Luxo Jr. (1986) first computer animation to be nominated for an Academy Award Red's Dream (1987) Tin Toy (1988) first computer animation to win an Academy Award Knick Knack (1989)

23 Early CG in film Future World (1976) Star Wars (1977) Tron (1982, MAGI) Supposed to look like a computer The Last Starfighter (1984) Use CG in place of models Willow (1988, ILM) Morphing video First digital blue screen matte extraction The Abyss (1989, ILM) Lawnmower man (1992, Xaos, Angel Studios) Hollywood s view of VR

24 Early CG in film Jurassic Park (1993, ILM) Forrest Gump (1994, Digital Domain) Insert CG ping pong ball Babe (1995, Rhythm & Hues) Move mouths of animals & fill in background Toy Story (1995, Pixar & Disney) First full length fully CG 3D animation

25 Early CG on TV Reboot (1995, Limelight Ltd. BLT Productions) Similar intention of inside computer First fully 3D Sat. morning cartoon Babylon 5 (1995) Routinely used CG models as regular features Simpsons (1995 PDI)

26 More recent movies with CG Final fantasy (2001) Fully 3D simulated environment Lord of the Rings ( ) One of the first movies using crowds (Massive) Polar express (2004) Fully motion-capture based Avatar (2009) Benjamin Button (2008)

27 Animation Principles 1. Squash and Stretch 2. Timing and Motion 3. Anticipation 4. Staging 5. Follow Through and Overlapping Action 6. Straight Ahead Action vs. Pose-to-Pose Action 7. Slow-in and Slow-out 8. Arcs 9. Exaggeration 10. Secondary Action 11. Appeal

28 1. Squash and Stretch Teaches basic mechanics of animation. Defines rigidity of material. Important in facial animation.

29 Squash and Stretch Cont. Can relieve the disturbing effect of strobing.

30 2. Timing and Motion Gives meaning to movement. Proper timing is critical to making ideas readable. Examples: Timing: tiny characters move quicker than larger ones. Motion: can suggest object weight

31 3. Anticipation Preparation for an action Example: Goofy prepares to hit a baseball.

32 4. Staging A clear presentation of an idea. Some Techniques: Use motion in a still scene or use of static movement in a busy scene. Use of silhouettes (on the side)

33 5. Follow Through and Overlapping Action 1. Follow Through Termination part of an action. Example: after throwing a ball 2. Overlapping Action Starting a second action before the first has completed. Example: Luxo Jr. s hop with overlapping action on chord.

34 6. Straight Ahead Action and Poseto-Pose Action 1. Straight Ahead Animator start from first drawing in the scene and draw all subsequent frames until the end of scene. 2. Pose-to-Pose Animator plans actions, draws a sequence of poses, in between frames etc.

35 7. Slow in and Out Spacing of in-between frames to achieve subtlety of timing and movement.

36 8. Arcs Visual path of action for natural movement Makes animation much smoother and less stiff than a straight line

37 9. Exaggeration Accentuating the essence of an idea via the design and the action Needs to be used carefully Example: Luxo Jr. made smaller to give idea of a child.

38 10. Secondary Action Action that results directly from another action. Used to increase the complexity and interest of a scene. Example: Body movement is the primary action, facial expression is the secondary action

39 11. Appeal Refers to what an audience would like to see. Character cannot be too simple (boring) or too complex. Examples: Avoid mirror symmetry, asymmetry is interesting.

40 Animation: Keyframing (related to in betweening ) Traditional animation technique Dependent on artist to generate key frames Additional, inbetween frames are drawn automatically by computer

41 Keyframing How are we going to interpolate? From The computer in the visual arts, Spalter, 1999

42 Linear Interpolation Simple, but discontinuous velocity

43 Nonlinear Interpolation Smooth ball trajectory and continuous velocity, but loss of timing

44 Easing Adjust the timing of the in-between frames. Can be automated by adjusting the step size of parameter t.

45 Animation/Image Illusions A really nifty set of techniques Perceptional psychology looks at these Also known as optical illusions Clever but hard to exploit automatically But you can try

46 Speed

47 Motion

48 Waves

49 Rotation

50 Color constancy A looks darker than B

51 Color constancy A looks darker than B

52 Color constancy A looks darker than B Why?

53 [Video] Examples

54 [Video] Supercool!