COMP 238 Advanced Image Generation

1

• COMP 238 Advanced Image Generation
• Anselmo Lastra
• lastra_at_cs.unc.edu
• SN256, 962-1958
• http//www.cs.unc.edu/lastra
• Office Hours?

2
Used to be Raster Graphics

• You may be able to guess history
• What came before raster graphics?

3
Web Page

• http//www.cs.unc.edu/lastra/comp238

4
Topics

• Raytracing
• Rendering Equation, etc.
• Radiosity
• Monte Carlo Methods
• Surface models

• Programmable Shading
• Image-Based Rendering
• Types of renderers
• Architectures and Parallel Rendering
• Volume rendering

5
What We Dont Cover

• Geometric topics
• Simplification
• Culling
• However, some latitude
• May want to look at LDITree and QSplat

6
Shading (some are hacks)

• Shadows
• Reflections
• Bump mapping (?)
• Procedural texturing (Perlin)
• Reaction/diffusion
• Should we work with RenderMan, Cg, or OpenGL 2.0?

7
IBR

• Light Fields, Lumigraph, Concentric Mosaics
• Plenoptic Modeling
• View Dependent Texture Mapping
• Light Field Mapping
• Unstructured Lumigraph
• ??

8
Student Presentation Topics

• Flocking
• Plants
• Particle systems
• Hierarchical Z

• High Dynamic Range
• Tone mapping
• Light Field Mapping
• NPR
• Participating media
• Fast ray tracing

Ill put suggestions on web page
9
What do you want to do?

• Which topics?
• Any recent papers?
• Let me know.

10
What Do You Know?

• Who has written ray tracer?

11
New Students

• Come see me to see if you have necessary
  background.

12
Assignments

• Raytracer, 2 parts, see web pages
• Basic
• Stochastic
• Shader
• RenderMan, NVIDIA Cg, OpenGL 2.0
• Image-Based Rendering?
• Final Project

13
Presentation

• Present a paper
• Including the background work necessary to
  understand
• Prefer individual presentations
• Depends on class size

14
Final project topic

• Mostly individual
• Group is a possibility discuss with me
• Clear topic with me
• I will come up with some suggestions you think
  and ask around also
• Opportunity to test waters on research area

15
Project Timelines

• Short writeup of project (about mid-term time)
• Background research
• Plan
• Final project (has been research quality)
• Written report
• Oral presentation

16
Schedule

• Ill make up when I count number of student
  presentations
• Apologies Ill be traveling too much
• Maybe we can fit in one or two classes at
  alternate time

17
Grading

• Weights
• Assignments/Presentation, 60
• Project Plan, 5
• Final Project, 35
• Incomplete only in case of emergency

18
Reference Books

• Roy Hall, Illumination and color in computer
  generated imagery
• Andrew Glassner, Principles of digital image
  synthesis
• Andrew Glassner, An Introduction to ray tracing
• Michael F. Cohen, John R. Wallace, Radiosity and
  realistic image synthesis
• Pete Shirley, Realistic Ray Tracing

19
Reference Books

• Jensen, Realistic Image Synthesis Using Photon
  Mapping
• Olano et al., Real-Time Shading
• Möller and Haines, Real-Time Rendering

20
Bookstore

• Listed Pete Shirleys book for this course
• Its only 35 or so
• Can get along without if youre on a budget

21
Resources

• ACM Digital Library
• Through our library, www.lib.unc.edu
• If youre off campus, you can set up proxy
  service. Youll need your PID.
• See http//proxy.lib.unc.edu/setupinfo.html
• I have SIGGRAPH course notes on my PC
• Name is lastra-cs
• Ill load 2002 as soon as I remember

22
Overview of Rendering Process

• Don Greenberg, et. al., A Framework for
  Realistic Image Synthesis, SIGGRAPH 97.
  http//www.graphics.cornell.edu/pubs/1997/GTS97.p
  df
• or the less technical version in
• Donald P. Greenberg. A framework for realistic
  image synthesis. Communications of the ACM,
  42(8)44--53, August 1999.
• Gives overview of process of simulation

23
Simulation

• CG often uses hacks to render images that look
  realistic
• Problems
• No idea how good
• No clear path to push further
• Use physics for simulation to establish formal
  basis

24
Steps

• Create reflection models
• Measure
• Model mathematically
• Light transport simulation
• Local
• Global
• Tone mapping
• Often none or just gamma correction

25
Steps Not Mentioned in Cornell Paper

• Geometric modeling
• Reconstruction
• and errors in both of these steps

26
Reflection/Material Models

• Measurement
• Tables
• Approximating Functions
• McAllisters dissertation work
• Data available
• Procedural shading

27
Light Transport

• Ray Tracing (including Monte Carlo methods)
• Some subset of lights paths modeled
• Specular most common (shiny spheres)
• Specular-diffuse and diffuse-diffuse
• Radiosity
• Diffuse surfaces
• Computed using boundary element methods or path
  tracing (trace rays with no branching and Monte
  Carlo methods).

28
Display

• Greenberg paper discusses mostly tone
  reproduction and perception
• Typical scenes exhibit high dynamic range
• Devices limited
• Human visual system perceives more dynamic range
• Human perception used in rendering

29
How Does IBR Fit in?

• Record/Replay
• Modeling (geometry/illumination)
• For given quality, youll see a tradeoff between
  accuracy of geometry and number of images.

30
Next Time

• Classical Ray Tracing
• Unless everyone knows this

31
Read

• Turner Whitteds original CACM paper on ray
  tracing.
• Link on class web page
• http//www.cs.unc.edu/lastra/Courses/Papers/Whitt
  ed_Ray_Tracing.pdf
• Begin on Pete Shirleys book
• Chapters 1-5 are intro