Post on 03-Jan-2016
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Lecture 15 of 42
William H. Hsu
Department of Computing and Information Sciences, KSU
KSOL course pages: http://snipurl.com/1y5gc
Course web site: http://www.kddresearch.org/Courses/CIS636
Instructor home page: http://www.cis.ksu.edu/~bhsu
Readings:
Disregard This Play aka Bingo: http://www.youtube.com/watch?v=SVtU5OS0c9A
SIGGRAPH 2007 highlights: http://www.youtube.com/watch?v=feBKaTJD-TA
Chapter 5, Eberly 2e – see http://snurl.com/1ye72
Computer-Generated Animation (CGA)Overview
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Lecture Outline
Animation Problems
Previsualization
Modeling
Keyframing
Dynamics and Interpolation
Lighting
Fast Previsualization
Modeling
Keyframe Interpolation
Position
Orientation
Scale
Camera Animation
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Let’s talk about computer animationLet’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?
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Computer AnimationComputer Animation
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
KeyframingKeyframing
Traditional animation technique Dependent on artist to generate ‘key’ frames Additional, ‘inbetween’ frames are drawn automatically by
computer
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
KeyframingKeyframing
From “The computer in the visual arts”, Spalter, 1999
How are we going to interpolate?
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Linear InterpolationLinear Interpolation
Simple, but discontinuous velocity
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Nonlinear InterpolationNonlinear Interpolation
Smooth ball trajectory and continuous velocity, but loss of timing
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
EasingEasing
Adjust the timing of the inbetween frames. Can be automated by adjusting the stepsize of parameter, t.
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Style or Accuracy?Style or Accuracy?
Interpolating timecaptures accuracyof velocity
Squash and stretchreplaces motionblur stimuli andadds life-likeintent
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Traditional MotivationTraditional Motivation
Ease-in andease-out is likesquash andstretch
Can weautomate theinbetweens forthese?
“The Illusion of Life, Disney Animation”Thomas and Johnson
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
More squash and stretchMore squash and stretch
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Anticipation and StagingAnticipation and Staging
Don’t surprise theaudience
Direct their attention to what’simportant
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Follow ThroughFollow Through
Audience likes to see resolution of action Discontinuities are unsettling
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
CombinedCombined
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Secondary MotionSecondary Motion
Characters should exist in a real environment Extra movements should not detract
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Interpolation [1]Interpolation [1]
Many parameters can be interpolated to generate animation Simple interpolation techniques can only generate simple
inbetweens More complicated inbetweening will require a more complicated
model of animated object and simulation
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Strengths Animator has exacting control (Woody’s face)
Weaknesses Interpolation hooks must be simple and direct
Remember the problems with Euler angle interp?
Time consuming and skill intensive Difficult to reuse and adjust
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Interpolation [2]Interpolation [2]
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Cartoon Physics Homer3D
Adapted from slides © 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
MoviesMovies
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
ExamplesExamples
Sports video games Madden Football
Many movie characters Phantom Menace
Cartoons
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Motion Capture StrengthsMotion Capture Strengths
Exactly captures the motions of the actor Michael Jordan’s video game character will capture his style
Easy to capture data
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Motion Capture WeaknessesMotion Capture Weaknesses
Noise, noise, noise! Magnetic system inteference Visual system occlusions Mechanical system mass Tethered (wireless is available now)
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Motion Capture WeaknessesMotion Capture Weaknesses
Aligning motion data with CG character Limb lengths Idealized perfect joints
Reusing motion data Difficult to scale in size (must also scale in time) Changing one part of motion
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Motion Capture WeaknessesMotion Capture Weaknesses
Blending segments Motion clips are short (due to range and tethers) Dynamic motion generation requires blending at run time Difficult to manage smooth transition
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
MoviesMovies
Animating aliens – progress since late 1990s Retargeting motion – SIGGRAPH Highlight reels – SIGGRAPH 2007 and beyond
Adapted from slides © 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
ExamplesExamples
Inanimate video game objects GT Racer cars Soapbox about why this is so cool
Special effects Explosions, water, secondary motion Phantom Menace CG droids after they were cut in half
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Procedural AnimationProcedural Animation
Very general term for a technique that puts more complex algorithms behind the scenes
Technique attempts to consolidate artistic efforts in algorithms and heuristics
Allows for optimization and physical simulation
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Procedural Animation StrengthsProcedural Animation Strengths
Animation can be generated ‘on the fly’ Dynamic response to user Write-once, use-often Algorithms provide accuracy and exhaustive search that
animators cannot
© 2001 Brogan, D., University of Virginia
CS 445 (Undergrad) / CS 645 (Graduate) – Introduction to Computer Graphics
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Summary
Animation Problems
Previsualization
Modeling
Keyframing
Dynamics and Interpolation
Lighting
Modeling
Keyframe Interpolation
Position
Orientation
Scale
Computing & Information SciencesKansas State University
Lecture 15 of 42CIS 636/736: (Introduction to) Computer Graphics
Terminology
Tasks
Previsualization
Modeling
Keyframing
Lighting
Keyframe Interpolation
Dynamics
Forward – ballistic simulation
Inverse – ballistics (fire control)
Kinematics
Forward – simulation of articulated model
Inverse – control of articulated model