Computer Graphics

Overview • Administrivia ! People, times, places, etc.

Computer Graphics

• Syllabus ! What will I learn in this course?

• Raster Graphics Adam Finkelstein Princeton University

! Getting started …

COS 426, Spring 2005

Administrative Matters • Instructors ! Adam Finkelstein - CS 424, stop in any time, or email ! Jason Lawrence (TA) - CS 415, office Thur 4:30-5:30

• Book ! Computer Graphics with OpenGL, Third Edition, Donald Hearn and M. Pauline Baker, Prentice Hall, 2004! ISBN: 0-13-015390-7

• Web page ! http://www.cs.princeton.edu/courses/cos426

Coursework • Exams (30%) ! In class (Mar 10 and Apr 26)

• Programming Assignments (40%) ! ! ! !

Assignment #1: Image Processing (due Feb 20) Assignment #2: Ray Tracing (due Mar 20) Assignment #3: Modeling (due Apr 3) Assignment #4: Animation (due Apr 17)

• Final Project (20%) ! Do something cool! (due at end of semester)

• Class Participation (10%)

Programming Assignments • When? ! Roughly every two weeks

• Where?

Art Contest • Everybody should submit entries! ! 1 point for submitting ! 2 points for winning

! Anywhere you want, e.g. home or Friend 017 lab

• How? ! Windows (017), Unix/Linux (“hats”), or MacOSX ! C and C++, OpenGL, GLUT

• What? ! Basic feature lists ! Extra credit lists ! Art contest

Cool Images (Brian Beck, CS 426, Sprint04)

Videos (Jon Beyer, CS 426, Spring04)

Bloopers (Kathleen Mulcahey, CS 426, Fall99)

Collaboration Policy • Overview: ! You must write your own code (no credit for other code) ! You must reference your sources of any ideas/code

• It’s OK to …

Precepts • Schedule? ! Wednesday, 7-8PM

• Place? ! TBA

! Talk with other students about ideas, approaches, etc. ! Get ideas from information in books, web sites, etc. ! Get “support” code from example programs » But, you must reference your sources

• It’s NOT OK to … ! Share code with another student ! Use ideas or code acquired from another sources without attribution

Overview • Administrivia ! People, times, places, etc.

! Syllabus ! What will I learn in this course?

Introduction • What is computer graphics? ! ! ! !

Imaging = representing 2D images Modeling = representing 3D objects Rendering = constructing 2D images from 3D models Animation = simulating changes over time

• Raster Graphics ! Getting started …

Applications

Applications

• Entertainment

• Entertainment

• Computer-aided design


• Scientific visualization


• Training

• Training

• Education

• Education

• E-commerce

• E-commerce

• Computer art

• Computer art

Jurasic Park (Industrial, Light, & Magic)

Geri’s Game (Pixar Animation Studios)

Quake (Id Software)

Applications

Applications

• Entertainment

• Entertainment




• Scientific visualization Los Angeles Airport

• Training

(Bill Jepson, UCLA)

• Education

• Education

• E-commerce

• E-commerce

• Computer art

Airflow Inside a Thunderstorm

• Training

(Bob Wilhelmson, University of Illinois at Urbana-Champaign)

• Computer art

Gear Shaft Design (Intergraph Corporation)

Apo A-1

Boeing 777 Airplane

(Theoretical Biophysics Group, University of Illinois at Urbana-Champaign)

(Boeing Corporation)

Applications

Applications

• Entertainment

• Entertainment




• Scientific visualization Driving Simulation

• Training

(Evans & Sutherland)

• Training

• Education

• Education

• E-commerce

• E-commerce

• Computer art

• Computer art

Desk Assembly (Silicon Graphics, Inc.)

Flight Simulation

Forum of Trajan

(NASA)

Applications

• Entertainment

• Entertainment




• Scientific visualization Interactive Kitchen Planner

Human Skeleton (SGI)

(Bill Jepson, UCLA)

Applications

• Training

Visible Human (National Library of Medicine)

• Training

(Matsushita)

• Education

• Education

• E-commerce

• E-commerce

• Computer art

• Computer art Virtual Phone Store (Lucent Technologies)

Blair Arch (Marissa Range ‘98)

Syllabus

Part I: Image Processing

I. Image processing

• Raster Graphics ! Display devices ! Color models

II. Rendering III. Modeling Rendering

IV. Animation

(Michael Bostock, CS426, Fall99)

Image Processing (Rusty Coleman, CS426, Fall99)

• Image Representation ! Sampling ! Reconstruction ! Quantization & Aliasing

Image Composition (Michael Bostock, CS426, Fall99)

• Image Processing Modeling

Animation

(Dennis Zorin, CalTech)

(Angel, Plate 1)

Part II: Rendering

Filtering Warping Composition Morphing

Image Morphing (All students in CS 426, Fall98)

Part III: Modeling

• 3D Rendering Pipeline ! ! ! ! ! ! !

! ! ! !

• Representations of geometry

Modeling transformations Viewing transformations Hidden surface removal Illumination, shading, and textures Scan conversion, clipping Hierarchical scene graphics OpenGL

! Curves: splines ! Surfaces: meshes, splines, subdivision ! Solids: voxels, CSG, BSP OpenGL (Chi Zhang, CS 426, Fall99)

• Procedural modeling ! Sweeps ! Fractals ! Grammars

• Global illumination

Shell

! Ray tracing ! Radiosity

(Douglas Turnbull, CS 426, Fall99)

Scenery Designer

Ray Tracing

(Dirk Balfanz, Igor Guskov, Sanjeev Kumar, & Rudro Samanta, CS426, Fall95)

(James Percy, CS 426, Fall99)

Part IV: Animation

Overview

• Keyframing

• Administrivia

! Kinematics ! Articulated figures

! People, times, places, etc.

• Syllabus

• Motion capture ! Capture ! Warping

• Dynamics

! What will I learn in this course?

! Raster Graphics

Ice Queen

! Let’s get started …

(Mao Chen et al CS426, Fall98)

! Physically-based simulations ! Particle systems

• Behaviors ! Planning, learning, etc.

Animation (Jon Beyer, CS426, Spring04)

Raster Graphics

What is an Image?

• Images

• An image is a 2D rectilinear array of pixels

! What is an image? ! How are images displayed?

• Colors ! How do we perceive colors? ! How do we represent colors in a computer?

Continuous image

What is an Image?

What is an Image?


Continuous image

Digital image

A pixel is a sample, not a little square!

Image Acquisition • Pixels are samples from continuous function ! Photoreceptors in eye ! CCD cells in digital camera ! Rays in virtual camera

Digital image


Continuous image

Digital image

A pixel is a sample, not a little square!

Image Display • Re-create continuous function from samples ! Example: cathode ray tube

Image is reconstructed by displaying pixels with finite area (Gaussian)

Liquid Crystal Display (LCD)

Display Hardware • Video display devices » » ! ! !

Cathode Ray Tube (CRT) Liquid Crystal Display (LCD) Plasma panels Thin-film electroluminescent displays Light-emitting diodes (LED)

• Hard-copy devices

Figure 2.16 from H&B

Image Resolution

! ! ! ! !

Ink-jet printer Laser printer Film recorder Electrostatic printer Pen plotter

Frame Buffer

• Intensity resolution ! Each pixel has only “Depth” bits for colors/intensities

• Spatial resolution ! Image has only “Width” x “Height” pixels

• Temporal resolution

Typical Resolutions

! Monitor refreshes images at only “Rate” Hz

NTSC Workstation Film Laser Printer

Width x Height 640 x 480 1280 x 1024 3000 x 2000 6600 x 5100

Depth 8 24 12 1

Rate 30 75 24 -

Frame Buffer Figure 1.2 from FvDFH

Frame Buffer Refresh

Refresh rate is usually 60-75Hz

Color Frame Buffer

Figure 1.3 from FvDFH

Color CRT

Raster Graphics • Images ! What is an image? ! How are images displayed?

! Colors ! How do we perceive colors? ! How do we represent colors in a computer?

Figure 2.8 from H&B

Electromagnetic Spectrum

Visible Light

• Visible light frequencies range between ... ! Red = 4.3 x 1014 hertz (700nm) ! Violet = 7.5 x 1014 hertz (400nm)

• The color of light is characterized by … ! Hue = dominant frequency (highest peak) ! Saturation = excitation purity (ratio of highest to rest) ! Lightness = luminance (area under curve)

White Light Figures 15.1 from H&B

Color Perception

Figures 15.3-4 from H&B

Color Models Spectral-response functions of each of the three types of cones on the human retina.

• RGB • XYZ • CMY • HSV

Tristimulus theory of color

Figure 13.18 from FvDFH

Orange Light

• Others

RGB Color Model

RGB Color Cube R 0.0 1.0 0.0 0.0 1.0 1.0 0.0 1.0 0.5 1.0 1.0 0.5

Colors are additive

G 0.0 0.0 1.0 0.0 1.0 0.0 1.0 1.0 0.0 0.5 0.5 0.3

B 0.0 0.0 0.0 1.0 0.0 1.0 1.0 1.0 0.0 0.5 0.0 0.1

Color Black Red Green Blue Yellow Magenta Cyan White ? ? ? ? Figures 15.11&15.12 from H&B

Plate II.3 from FvDFH

RGB Spectral Colors

XYZ Color Model (CIE)

Amounts of RGB primaries needed to display spectral colors

?

Amounts of CIE primaries needed to display spectral colors


CIE Chromaticity Diagram


CIE Chromaticity Diagram

Normalized amounts of X and Y for colors in visible spectrum

(White)

Compare Color Gamuts


Identify Complementary Colors

Determine Dominant Wavelength and Purity

Figures 15.8-10 from H&B

RGB Color Gamut

CMY Color Model

Color gamut for a typical RGB computer monitor

Colors are subtractive

C 0.0 1.0 0.0 0.0 1.0 1.0 0.0 1.0 0.5 1.0 1.0

M 0.0 0.0 1.0 0.0 1.0 0.0 1.0 1.0 0.0 0.5 0.5


CMY Color Cube

Color White Cyan Magenta Yellow Blue Green Red Black ? ? ?

Plate II.7 from FvDFH

HSV Color Model H 0 120 240 * * * 60 270 270


Summary • Images ! ! ! !

Y 0.0 0.0 0.0 1.0 0.0 1.0 1.0 1.0 0.0 0.5 0.0

Pixels are samples Frame buffers Display hardware (CRTs, LCDs, printers, etc.) Devices have limited resolution

• Colors ! Tristimulus theory of color ! CIE Chromaticity Diagram ! Different color models for different devices, uses, etc.

S 1.0 1.0 1.0 0.0 0.0 * 1.0 0.5 0.0

V 1.0 1.0 1.0 1.0 0.5 0.0 1.0 1.0 0.7

Color Red Green Blue White Gray Black ? ? ?

Figure 15.16&15.17 from H&B