Quiz 3, Go to cs.northwestern/~animation/Project3/project.php

1. Quiz 3, Go to www.cs.northwestern.edu/~animation/Project3/project.php Please list the author and basic scene description. Write notes for our in-class critique based upon the following criteria (positive and negative comments) • Created a Scene (backdrop & ground-plane): • Hero lighting • Is it obvious where the viewer should be looking: • Interesting composition & sense of relationship: • Shadows • Mood lighting: • Same objects, same composition, same camera angle as hero lighting: • Different light focusing on different character: • Conveys mood: • Main character still visible: • Main character still belongs to scene: • Shadows

2. Business • Thanks carefully naming your Project 3 files • (Your TA appreciates it :) • Final project proposal round 2 due Thursday • Start a web page (HTML format) • Who's in your group • Overview with Goals • Time table (schedule for what will be done when) • Include model sheets, story boards, material examples, etc

3. Character Modeling: Key Frame Animation Amy Gooch CS395: Intro to Animation Summer 2004

4. 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

5. 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

6. Animation • 3D Scene does not have • Gravity • Weight • Force • interactions between objects • (bit of a lie) • You must make it seem so!

7. Preproduction Phases • Screen-play • Storyboards • Character development

8. 3D Characters • Digital actor • Tin can • Sack of flower • Butterfly, beetle • Bird • Flower • Robot • Humanoid • Etc…

9. Typical Character • Mechanics of movement must be convincing • Skin and clothing moves & bends appropriately • This process of preparing character controls is called rigging • Fully rigged character has • Skeleton joints, surfaces, deformers, expressions, Set Driven Key, constraints, IK, Blendshapes, etc

10. Typical Character

11. Character Resolution • Use low resolution character that has surfaces “parented” to skeleton • Allows interactive animations • Switch to full resolution character later • Rag Doll; Skeleton by Proxy tutorialhttp://www.goldenxp.com/tutorials/ragdoll/ragdoll1.htm

12. Typical Character Animation Workflow • Character Design • Model • Skeleton Rigging • Binding • Animation • Integration • Rendering

13. For Project 4 • Concentrate on • Character Design • Model Sheet with poses • Modeling (simple) • Skeleton Rigging • Binding

15. 12Principles.ppt

16. Thursday • Quiz • Character Model Sheets due • Read Project 4 Web page carefully

18. Character Modeling: Key Frame Animation Amy Gooch CS395: Intro to Animation Summer 2004

19. Primary methods of Animation • Keyframe • Procedural • Expressions • Scripting • Dynamics/Simulation • Physics • Motion Capture • Combinations of the above

20. 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

21. 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

22. Motion Curves: Position vs. Time

23. 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?

24. 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

25. Smooth Interpolation Soft changes of direction

26. Linear Interpolation Hard changes of direction Appears to be contacting other objects, instant changes

27. Step Interpolation Object reappears in a totally different position This is very useful. When?

28. 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

29. 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!

30. Motion of characters • Along with key frame animation we can use kinematics • Kinematics = study of motion without regard to the forces that cause it Specify fewer degrees of freedom More intuitive control

31. User Control of Kinematic Characters • Joint Space • Position all joints (fine level of control) • Cartesian Space • Specify environmental interactions easily • Most DOF computed automatically

32. Inverse Kinematics • Balance = keep center-of-mass over support polygon • Control • Ex: position vaulter’s hands on line between shoulder and vault • Ex: Compute knee angles that will give runner the right leg length

33. What makes IK hard • Redundancy

34. What makes IK hard • Singularities

35. What make IK hard • Goal of “natural looking” motion • Minimum jerk • Equilibrium point trajectories

36. 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

37. Credits • Winny • Jessica Hodgins • http://www.cs.dartmouth.edu/~brd/Teaching/Animation/animation.html