Animation CS 551 / 651

1. AnimationCS 551 / 651 David Brogan dbrogan@cs.virginia.edu

2. Introduction • We are going to study how things move and the creation of computer graphics representations that look “good enough” • Renderingis: mapping light sources and surfaces to a vector of pixel colors • Animationis: mapping objects, intentions, and external forces to a vector of new object positions / orientations

3. We will not • Develop drawing skills • but we may study how others draw so we can automate the process • Learn how to use Maya • but we may use Maya as a rendering tool • Hone our video game or moviemaking skills • but we will study how modern animation technology contributes to video games and what elements of moviemaking artistry (timing, camera angles, etc.) must reside in animation tools

4. Biomechanists • Physics and sensors • Artists • Intuition and mind’s eye Study how things move • Who else does this?

5. Study how things move • We’ll investigate • Human walking, running, dancing • Bicycle riding • Group behaviors • Rigid body dynamics

6. Generate graphics that is “good enough” MonetLa Cathédrale de Rouen (1894) PicassoThe Bull (1946) • Who else studies this? • Perceptual psychologists • Artists University of Utah

7. Generate graphics that is “good enough” • We’ll investigate • Recent perceptual literature (change blindness) • Recent computer animation experiments (faking physics)

8. Completing the mapping • Bridge gap between knowledge of how things move to how they need to be rendered • Artists use their minds and hands • Computer scientists use math and programs

9. Traditional techniques • Keyframing (Shoemake) • Orientation reps (quaternion, euler) • Curve reps (linear, quadratic, wavelets) • Interpolation (computing arclength, Gaussian Quadrature, SLERP) • Disney artists (Johnson) • Timing / storyboarding

10. Numerical Methods • Curve fitting (least squares) • Optimization • Simulated annealing (Numerical Recipes) • Simplex • Spacetime Constraints (Witkin & Kass) • Genetic Algorithms (Sims) • Neural Networks (Grzeszczuk)

11. Human Motion • Motion Capture • Retargeting (Gleicher, J. Lee, Z. Popovic, Arikan) • Blending (Rose) • Abstraction (Unuma) • Walking • Biomechanics (McMahon, Ruina) • Gait Generation (Metaxas, van de Panne, Hodgins)

12. Physical Simulation • Rigid Body • Physics for games (Hecker) • Featherstone’s Method • Constraint satisfaction • Integration • Runge-Kutta • Euler • Simplification (Chenney, Lin, Popovic) • Perception (O’Sullivan, Proffitt)

13. Autonomous Agents • Behaviors (Thalmann, Badler, Blumberg) • Group actions (Reynolds, Brogan, Helbing)

14. Administrivia • Syllabus • Instructor/TA coordinates • Prereqs • Reading Material • Assignments • Grading & Honor Code • Topic list

15. Instructor / TA Coordinates • Professor Brogan • Olsson 217 • 982-2211 • dbrogan@cs.virginia.edu • Available in office or through email appointments • TA TBD

16. Prerequisites • Intro to Graphics • OpenGL skills • User interface toolkits • Appreciation for rendering equations • Mathematics (familiarity with…) • Multivariate / Differential Calculus • Probability / Statistics • Linear Algebra • AI (familiarity with…)

17. Reading Material • No textbook • Good ones to consult: • Lots of research papers • I’ll provide background lectures • Research papers provide demonstrations

18. Assignments • Approximately five programming assignments • Spacetime Constraints • Inverse Kinematics • Motion Capture Reuse / Retarget • Rigid-body Dynamical Simulator • High-level Control Systems

19. Assignments • Approximately four homework assignments • Emphasize the fundamentals • Physical simulation • Least squares • Simulated annealing

20. Assignments • Course project? • We can talk about it

21. Assignments • Class Participation • Due to the seminar aspect of course, participation is required • Presentation of a paper • Contribution to discussions - You’ll have to be at most classes

22. Grading • Final scale will be set upon determination of grad / undergrad ratio and class size • Emphasis is on programming assignments • There will be a final (probably no midterm)

23. Honor Code • Initial Assumption (assume this as default) • All code is 100% you – no web, no other people • Relaxed Assumption • You can use the web • Relaxed Assumption • You can work with others • The operating assumption will be specified for each assignment

24. Perception • The only reason we’re able to have this class today is because our perceptual system is easily tricked (but it’s finicky) • Modeling perception really matters for computer animation

25. Perception • Positive afterimage (persistence of vision) • the visual stimulus that remains after illumination has changed or been removed • Motion blur • Persistence of vision causes an object to appear to be multiple places at once

26. Motion Blur • Virtual camera in computer graphics usually shoots with infinitely small shutter speed • No motion blur results • Without motion blur, 30 fps results in fast moving objects that look like they are strobing, or hopping

27. What’s the rate? • Playback rate • The number of samples displayed per second • Sample rate • The number of different images per second

28. Perception • Computer graphics rendering can rely on four-hundred years of perception research by artists • The best animators have is eighty years of Disney • In 1550, after 100 years of refining the art of perspective drawing, artists were shocked to think that the geometric purity of their modeled world didn’t map to recent discoveries of the human eye. They couldn’t even imagine how cognition affected what one “saw.” 200 more years would pass.

29. Animation timeline • Persistence of vision • Thaumotrope (1800s) • Flipbook • Zoetrope (1834) • Shadow puppets pbsKids

30. Animation timeline • Photography • Muybridge (1885) • Film projector (Edison, 1891)

31. Animation Timeline • First Animation • 1896, Georges Melies, moving tables • 1900, J. Stuart Blackton, added smoke • First celebrated cartoonist • Winsor McCay • Little Nemo (1911) • Gertie the Dinosaur (1914)

32. Animation Timeline • 1910, Bray and Hurd • Patented translucent cels (formerly celluloid was used, but acetate is used now) used in layers for compositing • Patented gray-scale drawings (cool!) • Patented using pegs for registration (alignment) of overlays • Patented the use of large background drawings and panning camera

33. Bray’s Studio Produced • Max Fleischer – Betty Boop • Paul Terry – Terrytoons • George Stallings – Tom and Jerry • Walter Lantz – Woody Woodpecker • 1915, Fleischer patented rotoscoping • Drawing images on cells by tracing over previously recorded live action (MoCap) • 1920, color cartoons

34. Disney • Advanced animation more than anyone else • First to have sound in 1928, Steamboat Willie • First to use storyboards • First to attempt realism • Invented multiplane camera

35. Multiplane Camera • Camera is mounted above multiple planes • Each plane holds an animation cel • Each plane can translate freely on 3 axes • What is this good for? Zooming, moving foreground characters off camera, parallax, prolonged shutter allows blurring some layers (motion blur)

36. Stop-motion Animation • Willis O’Brien – King Kong • Ray Harryhausen – Mighty Joe Young • Nick Park – Wallace and Grommit • Tim Burton – Nightmare Before Christmas

37. Animation Heritage • 1963 – Ivan Sutherland’s (MIT) Sketchpad • 1970 – Evans and Sutherland (Utah) start computer graphics program (and Co.) • 1972 – Ed Catmull’s (Utah) animated hand and face (later co-founded Pixar) • 1970’s – Norm Badler (Penn) Center for Modeling and Simulation and Jack

38. Animation Heritage • 1970’s – New York Institute of Technology (NYIT) produced Alvy Ray Smith (Cofounded Pixar and Lucasfilm) and Catmull • 1980’s – Daniel and Nadia Magnenant-Thalmann (Swiss Universities) become European powerhouses

39. Animation Heritage • 1980’s – z-buffer invented, SGI founded, and Alias/Wavefront founded • 1977 – Starwars • 1982 – Tron (first extensive use of gfx) • 1982 – Early use of particle systems (Star Trek II: The Wrath of Khan) • 1984 – The Last Starfighter (look for the Cray X-MP in credits)

40. Animation Heritage • 1986 – Young Sherlock Homes (first use of synthetic character in film) • 1986 – First digital wire removal (Howard the Duck) • 1988 – First digital blue screen extraction (Willow) • The Abyss (1989) Terminator II (1991) Casper (1995), Men in Black (1997)

41. Animation Heritage • ILM: Jurassic Park (1993), Jumangi (1995), Mars Attacks (1996), Flubber (1997), Titanic (1999) • Angel Studios: Lawnmower Man (1992) • PDI: Batman Returns (1995) • Tippett Studio: Dragonheart (1996), Starship Troopers (1997) • Disney: Beauty and the Beast (1991), Lion King (1994), Tarzan (1999) • Dreamworks: Antz, Prince of Egypt • Pixar: Toy Story, A Bug’s Life, Monster’s Inc.

42. Americans are hardest working Recent history • United Nations report from Sept 1, 2003 • $/worker-year • US = $60,728, Belgium (top EU) = $54,333 • hours/worker-year • US = Japan = 1825, EU = 1300 – 1800 • $/worker-hour • Norway, France, Belgium, US $38 $35 $34 $32 • Why is US on top of $/worker-year? • Best economies encourage widespread use of communications and information technology • Even though we’re fat, dumb, and happy – we don’t take month-long vacations and one-year maternity breaks

43. Let’s talk about computer animation • Must generate 30 frames per second of animation (24 fps for film) • Issues to consider: • Is the goal to replace or augment the artist? • What does the artist bring to the project? • Is the scene/plot fixed or responsive to user? • What can we automate?

44. Animation – A broad Brush • Traditional Methods • Cartoons, stop motion • Keyframing • Digital inbetweens • Motion Capture • What you record is what you get • Simulation • Animate what you can model (with equations)

45. Computer Animation

46. Keyframing • Traditional animation technique • Dependent on artist to generate ‘key’ frames • Additional, ‘inbetween’ frames are drawn automatically by computer

47. Keyframing How are we going to interpolate? From “The computer in the visual arts”, Spalter, 1999

48. Linear Interpolation Simple, but discontinuous velocity

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

50. Easing Adjust the timing of the inbetween frames. Can be automated by adjusting the stepsize of parameter, t.