Animation - PowerPoint PPT Presentation

Animation l.jpg
Download
1 / 75

Animation Low-Level behaviors Overview Keyframing Motion Capture Simulation Low-Level Behaviors Keyframing Motion Capture Simulation Generating Motion What matters? Quality of motion appropriate for rendering style and frame rate Controllable from UI Controllable from AI

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Download Presentation

Animation

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Animation l.jpg

Animation

Low-Level behaviors Overview

Keyframing

Motion Capture

Simulation

IAT 410


Low level behaviors l.jpg

Low-Level Behaviors

  • Keyframing

  • Motion Capture

  • Simulation

IAT 410


Generating motion l.jpg

Generating Motion

  • What matters?

    • Quality of motion appropriate for rendering style and frame rate

    • Controllable from UI

    • Controllable from AI

    • Personality of the animated character

IAT 410


Keyframe example l.jpg

Keyframe Example

IAT 410


Keyframing l.jpg

Keyframing

  • Fine level of control

  • Quality of motion depends on skill of animator

IAT 410


Motion capture l.jpg

Motion Capture

  • Natural-looking motion

  • Hard to generalize motions

    • Registration is difficult

    • “Weightless” according to professional animators

IAT 410


Motion capture images courtesy microsoft motion capture group l.jpg

Motion CaptureImages courtesy Microsoft Motion Capture Group

IAT 410


Simulation broadly defined l.jpg

Simulation (Broadly Defined)

  • Physics is hard to simulate

  • Pseudo-physics is somewhat hard

  • Control is very hard

  • Gives Generalization + Interactivity

Desired

Behavior

Forces and Torques

Model

Numerical Integrator

User/AI

Control

State

Graphics

IAT 410


When to use what method l.jpg

When to Use What Method?

  • Keyframing

    • Sprites and other simple animations

    • Non-human characters

    • Coarse collision detection

  • Motion Capture

    • Human figures

    • Subtle motions, long motions

  • Simulation

    • Passive simulations

    • When interactivity w/ motion is important

IAT 410


Keyframing10 l.jpg

Keyframing

IAT 410


Keyframing11 l.jpg

Keyframing

IAT 410


Keyframe example12 l.jpg

Keyframe Example

IAT 410


Keyframing13 l.jpg

Keyframing

  • Fine level of control

  • Quality of motion depends on skill of animator

IAT 410


Hand drawn animation 2d l.jpg

Hand Drawn Animation -- 2D

  • Sketches

  • Pencil tests

  • Inking

  • Coloring

  • Digitize to sprites

IAT 410


Computer animation 2d or 3d l.jpg

Computer Animation: 2D or 3D

  • Sketches

  • Models and materials

  • Key configurations

  • Playback of motion or render to sprites

IAT 410


Keyframing16 l.jpg

The development process:

Adjust trajectory

Playback motion

Parameters:

Locations

Joint angles

Shape -- flexible objects

Material properties

Camera Motion

Lighting

Keyframing

IAT 410


Keyframing interpolation l.jpg

Keyframing Interpolation

  • Inbetweening

v

1,2,3 4 5 6 7,8,9…

Linear

time

v

1,2,3 4 5 6 7,8,9…

Slow in, Slow out

time

IAT 410


Interpolation example l.jpg

Interpolation Example

IAT 410


Key frames l.jpg

Key Frames

1

2

3

IAT 410


Key frames20 l.jpg

Key Frames

  • Timeline

  • 1 2 3 3 1

IAT 410


Inbetweening l.jpg

Inbetweening

  • Frame dependent (“wrong”) slow-in/out

    • Iterate once per frame

    • This is a variant on the Infinite Impulse Response (IIR) filter:

IAT 410


Inbetweening22 l.jpg

Inbetweening

  • Frame-Independent (“right”) slow in/out

    • Compute acceleration a

Time of last frame

Time

Tend

IAT 410


Spline driven animation l.jpg

Spline-driven Animation

y

x,y = Q(u)

for u:[0,1]

  • Equal arc lengths

  • Equal spacing in u

x

IAT 410


Reparameterize arc length l.jpg

Reparameterize Arc Length

  • S= A(u) = arc length

  • Reparam:

  • Find:

    Bisection search for a value

    of u where A(u) = S with a

    numerical evaluation of A(u)

    (Details in Watt & Watt)

IAT 410


Keyframing constraints l.jpg

Keyframing -- Constraints

  • Joint limits

  • Position limits

  • Inverse kinematics

IAT 410


Keyframing constraints26 l.jpg

Keyframing -- Constraints

IAT 410


Coordinate systems l.jpg

Coordinate Systems

IAT 410


Kinematics l.jpg

Kinematics

  • The study of motion without regard to the forces that cause it

Draw graphics

Specify fewer Degrees Of

Freedom (DOF)

More intuitive control of DOF

Pull on hand

Glue feet to ground

IAT 410


Inverse kinematics l.jpg

Inverse Kinematics

IAT 410


Inverse kinematics30 l.jpg

Inverse Kinematics

IAT 410


What makes ik hard l.jpg

What makes IK Hard?

  • Many DOF -- non-linear transcendental equations

  • Redundancies

    • Choose a solution that is “closest” to the current configuration

    • Move outermost links the most

    • Energy minimization

    • Minimum time

IAT 410


Ik difficulties l.jpg

IK Difficulties

  • Singularities

    • Equations are ill-conditioned near singularities

    • High state-space velocities for low Cartesian velocities

  • Goal of “Natural Looking”motion

    • Minimize jerk (3rd derivative)

IAT 410


Motion capture33 l.jpg

Motion Capture

  • What do we need to know?

    • X, Y, Z

    • Roll, Pitch, Yaw

  • Errors cause

    • Joints to come apart

    • Links grow/shrink

    • Bad contact points

  • Sampling Rate and Accuracy

IAT 410


Motion capture34 l.jpg

Motion Capture

  • Goals:

    • Realistic motion

    • Lots of different motions (300-1000)

    • Contact

  • Appropriate game genres

    • Sports

    • Fighting

    • Human characters

IAT 410


Applications l.jpg

Applications

Movies, TV

Video games

Performance animation

IAT 410


Slide36 l.jpg

IAT 410


Slide37 l.jpg

IAT 410


Plan out shoots carefully l.jpg

Plan out Shoots Carefully

  • Know needed actions (80-100 takes/day)

    • Bridges between actions

    • Speed of actions

    • Starting/ending positions

  • Hire the right actor

    • Watch for idiosyncrasies in motion

    • Good match in proportions

IAT 410


Sensor placement l.jpg

Sensor Placement

  • Place markers carefully

    • Capture enough information

    • Watch for marker movement

  • Check data part way through shoot

  • Videotape everything!

IAT 410


Slide40 l.jpg

IAT 410


Technology l.jpg

Technology

  • Numerous technologies

  • Record energy transfer

    • Light

    • Electromagnetism

    • Mechanical skeletons

IAT 410


Technology42 l.jpg

Technology

  • Passive reflection – Peak Performance Tech

    • Hand or semi-automatically digitized

    • Video

    • Time consuming

  • Issues

    • No glossy or reflective materials

    • Tight clothing

    • Marker occlusion by props

    • High frames/sec

IAT 410


Technology43 l.jpg

Technology

  • Passive reflection --Acclaim, Motion Analysis

    • Automatically digitized

    • 240Hz

    • Not real-time, Correspondence

    • 3+ markers/body part

    • 2+ cameras for 3D position data

IAT 410


Technology44 l.jpg

Technology

  • Vicon Motion Systems

    • Retroreflective paint on reflectors

    • Lights on camera

    • Very high contrast markers

IAT 410


Technology45 l.jpg

Technology

  • Active light sources -- Optotrak

    • Automatically digitized

    • 256 markers

    • 3500 marker/sec

    • Real-time

    • Specialized cameras

IAT 410


Technology46 l.jpg

Technology

  • Electromagnetic Transducers

    • Ascension Flock of Birds, etc

    • Polhemus Fastrak, etc

  • Limited range/resolution

    • Tethered (cables to box)

    • Metal in environment (treadmill,Rebar!)

    • No identification problem

    • 6DOFRealtime

    • 30-144 Hz13-18 markers

IAT 410


Technology47 l.jpg

Technology

  • Exoskeleton + angle sensors

    • Analogous

    • Tethered

    • No identification problem

    • Realtime- 500Hz

    • No range limit- Fit

    • Rigid body approximation

IAT 410


Technology48 l.jpg

Dataglove

Low accuracy

Focused resolution

Monkey

High accuracy

High data rate

Not realistic motion

No paid actor

Technology

Mechanical motion capture

IAT 410


Technology49 l.jpg

Technology

  • Technology issues

    • Resolution/range of motion

    • Calibration

    • Accuracy

    • Occlusion/Correspondence

IAT 410


Animation issues l.jpg

Animation Issues

  • Style

  • Scaling

  • Generalization

IAT 410


Resolution l.jpg

Resolution

  • Positioning of camera

IAT 410


Markers calibration l.jpg

Markers, Calibration

  • Marker Placement

    • Location should move rigidly with joint

    • Stay away from bulging muscles, loose skin

    • Shoulders: Skeletal motion not closely tied to skin motion

  • Calibration

    • Zero position

    • Fine calibration by hand

IAT 410


Calibration l.jpg

Calibration

  • Finding Joint Locations

    • Move markers to joint centers

      • Assume rigid links, rotary joints

  • Shoulder?

IAT 410


Calibration54 l.jpg

Calibration

  • Extract best limb lengths

  • Use estimator to compute limb length

  • Minimize or reject outliers

IAT 410


Calibration55 l.jpg

Calibration

  • Example estimator:

    • 508 frames of walking

    • 6 bad frames

    • Collarbone to shoulder:

      • Hand editing: 13.3cm

      • Estimator: 13.2cm

      • Arithmetic mean: 14.1cm

IAT 410


Accuracy l.jpg

Accuracy

  • Marker movement

  • Noise in sensor readings

  • Skew in measurement time

  • Environment restrictions

  • Frame rate

    • High frame rate allows good filtering

IAT 410


Camera calibration l.jpg

Camera Calibration

  • Internal camera parameters

    • Optical distortion of lens

  • External parameters

    • Position and orientation

  • Correlation between multiple cameras

IAT 410


Model based techniques l.jpg

Model-Based Techniques

  • Restricted search space for markers

  • Dynamics (velocity integration)

    • No infinite accelerations

  • Model of behavior

  • Model of bodies of occlusion

    • Objects don’t pass through each other

IAT 410


Scaling animation l.jpg

Scaling Animation

  • Contact

  • Movement style

  • Inverse kinematics

IAT 410


Generalizating animation l.jpg

Generalizating Animation

  • Interpolation Synthesis for Articulated Figure Motion

  • Wiley and Hahn

  • IEEE CG&A v17#6

IAT 410


Generalizating animation61 l.jpg

Generalizating Animation

  • Keyframes as constraints in a smooth deformation

    • Create functions by hand that warp the joint angle curves through time

  • Keyframe placing the ballon the racket at impact

    Motion Warping

    Witkin and Popovic, SIGGRAPH’95

IAT 410


Motion warping l.jpg

Motion Warping

  • For each joint angle curve C(t)

  • Cnew(t) = C(t) * A(t) + B(t)

  • A(t) is usually a smooth, gentle curve

IAT 410


Generalizating animation63 l.jpg

Generalizating Animation

  • Motion Editing With Spacetime Constraints

    • Michael Gleicher

    • 1997 Symposium on Interactive 3D Graphics

IAT 410


Blending animations l.jpg

Blending Animations

  • Efficient Generation of Motion Transitions Using Spacetime Constraints

    • Rose, Guenter, Bodenheimer, Cohen

    • Siggraph ’96

    • Uses dynamics to computeplausible paths

    • Blends these paths

IAT 410


Simulation l.jpg

Simulation

  • Modeling the real world with simple physics

    • Realism

    • A set of rules

    • Better interactivity

  • Objects or Characters

IAT 410


Passive no muscles or motors l.jpg

Passive -- No muscles or motors

Active -- Internal source of energy

IAT 410


Equations of motion l.jpg

Equations of Motion

  • Water

  • Explosions

  • Rigid body models

IAT 410


Control systems l.jpg

Control Systems

  • Wide variety of behaviors

  • Transitions between behaviors

  • Controllable by AI or UI

  • Robust

IAT 410


Equations of motion69 l.jpg

Equations of Motion

IAT 410


Generating motion70 l.jpg

Generating Motion

  • What matters?

    • Quality of motion appropriate for rendering style and frame rate

    • Controllable from UI

    • Controllable from AI

    • Skills of the animated character

    • Personality of the animated character

IAT 410


Keyframing71 l.jpg

Keyframing

  • Fine level of control

  • Quality of motion depends on skill of animator

IAT 410


Motion capture72 l.jpg

Motion Capture

  • Natural-looking motion

  • Hard to generalize motions

    • Registration is difficult

  • Often seems “weightless” – Bill Kroyer, Rhythm & Hues

IAT 410


Simulation broadly defined73 l.jpg

Simulation (Broadly Defined)

  • Physics is hard to simulate

  • Pseudo-physics is somewhat hard

  • Control is very hard

  • Gives Generalization + Interactivity

Desired

Behavior

Forces and Torques

Model

Numerical Integrator

User/AI

Control

State

Graphics

IAT 410


When to use what method74 l.jpg

When to Use What Method?

  • Keyframing

    • Sprites and other simple animations

    • Non-human characters

    • Coarse collision detection

  • Motion Capture

    • Human figures

    • Subtle motions, long motions

  • Simulation

    • Passive simulations

    • When interactivity w/ motion is important

IAT 410


Integration of technologies l.jpg

Integration of Technologies

  • Layering

    • Add hand/finger motion later

    • Facial animation

  • Use keyframing to modify data

    • Fix holes in data

  • Use motion capture to drive simulation

IAT 410


  • Login