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:
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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
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
Character Modeling: Key Frame
Animation
Amy Gooch
CS395: Intro to Animation
Summer 2004
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!
Preproduction Phases
• Screen-play
• Storyboards
• Character
development
3D Characters
• Digital actor
–
–
–
–
–
–
–
–
Tin can
Sack of flower
Butterfly, beetle
Bird
Flower
Robot
Humanoid
Etc…
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
Typical Character
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 tutorial
http://www.goldenxp.com/tutorials/ragdoll/ragdoll1.htm
Typical Character Animation
Workflow
•
•
•
•
•
•
•
Character Design
Model
Skeleton Rigging
Binding
Animation
Integration
Rendering
For Project 4
• Concentrate on
– Character Design
• Model Sheet with poses
– Modeling (simple)
– Skeleton Rigging
– Binding
12Principles.ppt
Thursday
• Quiz
• Character Model Sheets due
• Read Project 4 Web page carefully
Character Modeling: Key Frame
Animation
Amy Gooch
CS395: Intro to Animation
Summer 2004
Primary methods of Animation
• Keyframe
• Procedural
– Expressions
– Scripting
• Dynamics/Simulation
– Physics
• Motion Capture
• Combinations of the above
Keyframe Workflow
1. Set Keys
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–
Usually extreme positions
Less is more: Keys only the properties being
animated
2. Set Interpolation
–
–
Specify how to get from one key to another.
Secondary, but a necessary step.
3. 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: Position vs. Time
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Motion Curves
When is the box
going
• Forward?
• Backward?
• Fastest?
Is the box
• Starting from stop
or at rest?
• Stopping at the end
or continuing?
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
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Soft
changes
of
direction
Linear Interpolation
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Hard changes
of direction
Appears to be
contacting
other objects,
instant
changes
Step Interpolation
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Object
reappears
in a totally
different
position
This is very
useful.
When?
Ease In/Out
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Heavy objects take
a while to get going
• trains
Use interpolation to
emphasize this.
Ease in/out –orSlow 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!
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
User Control of Kinematic
Characters
• Joint Space
– Position all joints (fine level of control)
• Cartesian Space
– Specify environmental interactions easily
• Most DOF computed automatically
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
What makes IK hard
• Redundancy
What makes IK hard
• Singularities
What make IK hard
• Goal of “natural looking” motion
– Minimum jerk
– Equilibrium point trajectories
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