Introduction to Computer Graphics Introduction

1
Introduction toComputer Graphics- Introduction
-

• Marcus Magnor

2
Overview

• Today
• Administrative stuff
• Overview of computer graphics
• Fundamentals of image formation
• Next time
• Ray tracing fundamentals

3
General Information

• Blockveranstaltung
• 31
• Tue, Wed, Th 11.30-13.00 h
• Room M160
• Assignments
• Weekly
• Th Tue next week
• practical assignments
• Program your own ray tracer
• Provisional web page
• http//www.mpi-inf.mpg.de/departments/irg3/ws0506/
  cg/index.html
• Lecture slides (PDF), assignments, other
  information

4
People

• Lecturer
• Prof. Marcus Magnor
• Room G29
• E-mail magnor_at_mpi-sb.mpg.de
• Assistant
• Andrei Lintu
• At MPII
• Tel. [phone]
• E-mail lintu_at_mpi-sb.mpg.de
• Secretary
• Dr. Marion Zeiz
• Room G28
• Tel. [phone]

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Weekly Assignments

• Weekly assignments (Th to Tue)
• Programming assignments
• Submit your solution by following Tuesday
• E-mail program code to Andrei Lintu
• Feedback
• Correct program code provided on web page
• Discussion, QA via e-mail (chat ?)

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Programming Assignments

• On computers in student pool
• Standard ANSI C/C
• Must compile on any Linux system
• Send in compile-alone source code
• Standard libraries, library paths
• Provide Makefile
• Must compile and run on any Linux box
• Basis for ray tracing competition

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Ray Tracing Competition

• At the end of semester
• Technical part implement additional techniques
• Points for each implemented technique
• Bump mapping
• Shadow mapping
• Motion blur
• Artistic part create your own ray-traced work of
  art
• Picture must reflect all additionally implemented
  techniques
• Awards for best pictures
• Virtual exhibition on our web pages

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To pass the course

• Programming assignments
• Minimum of 30 per assignment sheet
• Average of gt50 of all assignments
• Ray Tracing competition
• Submit a picture created with your enhanced ray
  tracer
• Create accompanying web page explaining your
  techniques etc.
• Implement minimum number of technical points

9
Literature

• Frank Nielsen, "Visual Computing", Charles River
  Media, 2005, EUR 55,90
• Peter Shirley, "Realistic Ray-Tracing", AK
  Peters, 2003, EUR 40,00
• Alan Watt, Mark Watt, "Advanced Animation and
  Rendering Techniques, Addison-Wesley, 1992, EUR
  55,50
• Peter Shirley et al., "Fundamentals of Computer
  Graphics", AK Peters, 2005, EUR 81,50
• James Foley, Andries Van Dam, et al., "Computer
  Graphics Principles and Practice", 2. Edition,
  Addison-Wesley, 1995, EUR 81,50

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Course Syllabus

• Fundamentals
• light transport
• Ray Tracing
• Basics
• Transformations and projections
• Acceleration strategies
• Signal processing, antialiasing
• Advanced Topics
• Human visual system
• Perception
• Global illumination

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What is Computer Graphics ?
Engineering
Psychology
Photography
CAD/CAM/CAE
Rendering
Perception
Graphics
Simulation
Inverse Rendering
Geometric Modeling
Physics
Vision
Mathematics
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Image Perception - Image Formation
Scene Geometry Motion Surface Reflectance Scene
Illumination Camera
Models
Physics
Image
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Historical Perspective

• A short history of graphics
• 1950 MIT Whirlwind (CRT)
• 1955 Sage, Radar with CRT and light pen
• 1958 Willy Higinbotham Tennis
• 1960 MIT Spacewar on DEC PDP-1
• 1963 Ivan Sutherlands Sketchpad (CAD)
• 1969 ACM Siggraph founded
• 1968 Tektronix storage tube (5-10.000)
• 1968 EvansSutherland (flight simulators)
  founded
• 1968 Douglas Engelbart computer mouse
• 1970 Xerox GUI
• 1971 Gourand shading
• 1974 Z-buffer
• 1975 Phong model
• 1979 Eurographics founded
• 1980 Whitted Ray tracing

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Historical Perspective

• A short history of graphics (Cont.)
• 1981 Apollo Workstation, IBM PC
• 1982 Silicon Graphics (SGI) founded
• 1984 X Window System
• 1984 First Silicon Graphics Workstations (IRIS
  GL)
• Until mid/end of 1990s Dominance of SGI in the
  high end
• HW RealityEngine, InfiniteReality,
  RealityMonster, ...
• SW OpenGL, OpenInventor, Performer, Digital
  Media Libs, ...
• End of 1990sLow- to mid range taken over by
  PCs (Nvidia, ATI, ...)
• HW Fast development cycles, Graphics-on-a-chip,
  ...
• SW Direct 3D OpenGL, computer games
• Today
• Programmable graphics hardware, Cg

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Visual Entertainment
 
(1) Quelle SPIO, Spitzenorganisation der
Filmwirtschaft, Wiesbaden (2) Quelle FFA,
Filmförderanstalt, Berlin (3) Quelle
Titelprüfung der USK für Computerspiele (aller
Systeme), entspricht rd. 95 aller auf dem dt.
Markt publizierten Produktionen (4) Quelle Gfk,
Gesellschaft für Konsumforschung zitiert nach
VUD, Verband Unterhaltssoftware Dtld. e.V.
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Siggraph Publications 2001-2005
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Computer Graphics Industry

• Graphics hardware
• NVidia (USA)
• ATI (Canada)
• Software research
• Microsoft (USA, UK, China)
• Animation software
• Alias (Canada)
• Avid/SoftImage (USA/Canada)
• Autodesk (USA)

• Interactive entertainment
• Electronic Arts (USA)
• HEADQUARTERS Redwood City, California
• REVENUES 3.1 billion for fiscal 2005
• EMPLOYEES 6,100 worldwide  
• Sony, Nintendo, Sega (Japan)
• Ubi Soft (France)
• F/X
• Industrial Light Magic (USA)
• Digital Domain (USA)
• Pixar (USA)

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Industrial CG Jobs in Germany

• CAD, VR
• Airbus (Hamburg)
• Automotive industry
• Small- mid-cap companies
• Animation
• http//www.rendering.de/nano.cms/Lightwave/Jobange
  bote
• Game development
• Bundesverband der interaktiven Unterhaltungssoftwa
  re
• http//www.game-verband.de/
• Ubi Soft (Düsseldorf)
• Radon Labs, Zeroscale, SEK (Berlin)
• Crytek (Coburg)
• CG Research
• Mental Images, Mercury (Berlin)
• Alias, Scanline (Munich)

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Summary

• Computer Graphics
• Rendering, modeling, visualization, animation,
  imaging,
• Young, dynamic area
• Progress driven by research technology
• Big industry
• gtgt interactive entertainment, special effects
• Interdisciplinary field
• Mathematics, physics, engineering, psychology,
  art, entertainment,

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Introduction toComputer Graphics- Image
Formation -

• Marcus Magnor

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Motivation
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Image Formation
Sensor
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Perception of Light
The eye detects radiance
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Radiance in Space
Flux leaving surface 1 must be equal to flux
arriving on surface 2
The radiance in the direction of a light ray
remains constant as it propagates along the ray
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Brightness Perception
r
f
l

• dA gt dA photon flux per rod stays constant
• dA lt dA photon flux per rod decreases

• Where does the Sun turn into a star ?
• Depends on apparent Sun disc size on retina
• Photon flux per rod stays the same on Mercury,
  Earth or Neptune
• Photon flux per rod decreases when d? lt 1 arc
  minute (beyond Neptune)

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Light Object Interaction
Light/Object interaction
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Reflectance

• Reflectance may vary with
• Illumination angle
• Viewing angle
• Wavelength
• (Polarization)
• Variations due to
• Absorption
• Surface micro-geometry
• Index of refraction / dielectric constant
• Scattering

Aluminium ?2.0µm
Aluminium ?0.5µm
Magnesium ?0.5µm
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Surface Radiance

• Visible surface radiance
• Surface position
• Outgoing direction
• Incoming illumination direction
• Self-emission
• Reflected light
• Incoming radiance from all directions
• Direction-dependent reflectance

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Bidirectional Reflectance Distribution Function

• BRDF describes surface reflection for light
  incident from direction (??,f?) observed from
  direction (?i,fi)
• Bidirectional
• depends on two directions (4-D function)
• Distribution function
• Unit 1/sr

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BRDF Properties

• Helmholtz reciprocity principle
• BRDF remains unchanged if incident and reflected
  directions are interchanged
• Smooth surface isotropic BRDF
• reflectivity independent of rotation around
  surface normal
• BRDF has only 3 instead of 4 degrees of freedom

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BRDF Properties

• Characteristics
• BRDF units sr--1
• not intuitive
• Range of values
• from 0 (absorption) to
• ? (reflection, d -function)
• Energy conservation law
• No self-emission
• Possible absorption
• Reflection only at the point of entry (xi xo)
• No subsurface scattering

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BRDF Measurement

• Gonio-Reflectometer
• BRDF measurement
• point light source position (?,?)
• light detector position (?o ,?o)
• 4 degrees of freedom
• BRDF representation
• m incident direction samples (?,?)
• n outgoing direction samples (?o ,?o)
• mn reflectance values

Stanford light gantry
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Wrap-Up

• What you perceive is radiance
• Different objects reflect light differently
  Bidirectional Reflectance Distribution Function
  (BRDF)
• Light can be absorbed, scattered, bent,