Computer Animation Karen Liu associate professor at School of - - PowerPoint PPT Presentation

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Computer Animation Karen Liu associate professor at School of - - PowerPoint PPT Presentation

Feb 10, 2024 279 likes •1.08k views

Computer Animation Karen Liu associate professor at School of Interactive Computing Murali Varma graduate student at School of Interactive Computing Administrations http://www.cc.gatech.edu/classes/AY2012/ cs4496_spring Slides and

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Computer Animation

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Karen Liu

associate professor at School of Interactive Computing

Murali Varma

graduate student at School of Interactive Computing

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  • http://www.cc.gatech.edu/classes/AY2012/

cs4496_spring

  • Slides and assignments are online
  • No textbook, but there are reading materials
  • My office hours: Mon 12:15-1:30, TSRB 230A
  • TA office hours: Fri 2:00pm-3:15pm

Administrations

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Contact

  • Best way to get my attention
  • in class
  • office hours
  • Worst way to get my attention
  • emails
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  • Thorough understanding of linear algebra
  • Vector calculus
  • A good working knowledge of C and C++

programming

Prerequisites

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About Maya

  • You need to bring a laptop with Maya

installed on Friday

  • No prior knowledge in Maya is required
  • Simple Maya tutorial to help you start
  • http://students.autodesk.com
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OpenGL

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FLTK

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Tutorial on OpenGL and FLTK

  • OpenGL Tutorial: http://www.opengl.org/sdk/
  • One hour introduction lecture before Project 2 is assigned
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Get ready for this class

  • If you have a couple of hours this weekend
  • skim through the first three chapters of your
  • ld linear algebra textbook
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  • Given two vectors, a = (3, 0, 1) and b = (-2, 5,

2),

  • What is the dot product of a and b?
  • What is the cross product of a and b?
  • What is the norm of a?
  • What is the angle between a and b?
  • What is the projection of a on b?
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  • Given three n by n matrices A, B, and C
  • Is AB = BA true?
  • Is A(BC) = (AB)C true?
  • Is (AB)T = ATBT true?
  • Does A-1 always exist?
  • What is the rank of A?
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  • Reading assignment (0%)
  • Project 1 (15%)
  • Project 2 (20%)
  • Project 3 (20%)
  • Final project (20%)
  • Midterm (25%)

Grading schemes

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  • Project 1: Splines
  • Project 2: Particles
  • Project 3: Physics games
  • Final project: Inverse kinematics
  • Late policy: 33% reduction per day if you don’t have

a good reason

  • Everything has to be turned in before 10 am on the

due date

Projects and homework

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Partners

  • For project 3 and project 4, you will work with
  • ne partner
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  • Give you an overview of computer animation

with an emphasis on physics-based animation and character animation

  • Teach you how to be a good engineer who

also understands art

  • Inspire some of you to do research in

computer animation

What do I expect?

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  • A class that
  • takes a lot of your time (I’m not kidding)
  • tests your programming skills
  • makes you revisit linear algebra and

calculus

What should you expect?

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Course overview

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Traditional animation

That was then...

  • Film runs at 24 frames per sec;

that is, 1440 pictures to draw in

  • ne minute
  • Artistic vision has to be

converted into a sequence of still “keyframes”

  • Hard to draw consistent “in-

between” frames

  • Not enough to get the still right;

must to look right at full speed

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Computer assisted animation

This is now

  • Generate the images

by rendering a 3D model

  • Manually set the

parameters for each keyframe

  • Automatically

interpolate between two drawings to produce inbetweens

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Does it really get better?

Do computers really expedite the process of creating animation?

pencil and paper computer

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What can’t be done by keyframes?

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UNiGiNE

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NVIDIA Physx

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Physics simulation

  • It’s an algorithm that produces a sequence of

states over time under the laws of physics

  • What is a state?
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Simulation

xi ∆x

xi+1 xi+1 = xi + ∆x

xi

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Simulation

xi ∆x

xi+1

xi

xi+1 = xi + ∆x

Newtonian laws gravity wind gust elastic force

. . .

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Ordinary differential equations

An ODE is an equality equation involving a function and its derivatives

˙ x(t) = f(x(t))

known function time derivative of the unknown function unknown function that evaluates the state given time

F = ma

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Rigid bodies

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Rigid bodies

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Deformable objects

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Fluids

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Fluids

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And for my acting Oscar, I thank the special effects

“Acting is all about honesty, but something like this makes what you see on screen a dishonest moment,” said a leading technician (of Blood Diamond). “Everyone feels a bit dirty about it.”

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Fluids

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Fluids

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Fluid-solid coupling

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Water-thinshell interaction

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Melted

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Burned

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Drowned

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Deformed

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Crushed

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What can’t be done by simulation alone?

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Controlled simulation

Popovic et al Twigg and James

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Fluid control

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Fluid control

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Controlled interaction

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Character control

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Character animation

  • Unknown internal forces
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Simulation

xi ∆x

xi+1

xi

xi+1 = xi + ∆x

Newtonian laws gravity wind gust elastic force

. . .

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Simulation

xi ∆x

xi+1

Newtonian laws gravity wind gust elastic force

. . .

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Simulation

xi ∆x

xi+1

Newtonian laws gravity ground contact forces internal forces

. . .

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Character animation

  • Unknown internal forces
  • Natural human motion with variations
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Motion capture

Animals Humans Celebrities Objects

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What is captured?

Whole body Face Hands

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Optical systems

  • Cameras
  • High temporal resolution (120+ fps)
  • Detect the locations of reflective markers
  • Markers
  • Sensitive to infrared
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Raw data

3D locations of markers

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Inverse kinematics

  • Input: articulated body with handles + desired

handle positions

  • Joint angles that move handles to desired

positions

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Final motion

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Issues

The main problem with motion capture associated with characters has to do with mass distribution, weight and exaggeration. It is impossible for a performer to produce the kind of motion exaggeration that a cartoon character needs, and the mass and weight of the performer almost never looks good when applied to a character

  • f different proportions.

Eric Darnell, codirector of Antz

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Issues

The mapping of human motion to a character with non-human proportions doesn’t work, because the most important things you get out

  • f motion capture are the weight shifts and the

subtleties and that balancing act of the human body. If the proportions change, you throw all that out the door, so you might as well animate it.

Richard Chuang, VP at PDI

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Performance animation

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Performance animation

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Performance animation

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Other Topics

  • Facial animation
  • Cloth simulation
  • Hair modeling
  • Sound simulation
  • Crowd animation