© university of wisconsin cs 559: computer graphics prof stephen chenney spring 2002 cs559-1

© University of Wisconsin

CS 559: Computer Graphics

Prof Stephen Chenney

Spring 2002

http://www.cs.wisc.edu/~cs559-1


Today

• Course overview and information

• Getting started on images

• Programming assignment 1


What is Computer Graphics?

• Technically, it’s about the production, manipulation and display of images using computers

• Practically, it’s about movies, games, art, training, advertising, communication, design, …


Is 2D Graphics Important?

Compositing in movies: images arecreated in layers, and then combined

Sprites in games: Images are built by overlaying characters and objects on a background


Virtual Reality, the Iowa Driving Simulator

Augmented Reality, from Eric Grimson’s research group at MIT

3D is Sometimes Essential


Computer Graphics?

The Wooden Mirror, by Daniel Rozin

It consists of many small wooden blocks with a camera in the center. The camera takes an image, it is converted to intensities, and each block is rotated to reflect an appropriate amount of light.


This Course: Building Blocks

• Images and computers– Sampling, Color, Filters, …

• Drawing in 2D– Drawing lines and polygons, clipping, transformations

• Drawing in 3D– Viewing, transformations, lighting, the standard pipeline

• Modeling in 3D– Describing volumes and surfaces, drawing them effectively

• Miscellaneous interesting stuff– Raytracing, animation, …


People

• Professor Stephen Chenney– Room 6387

– Office Hours Tues 2-3, Thurs 10-11

– [email protected]

• TA: Matt Anderson– Office Hour TBD


• TA: Eric McDaniel– Office Hour TBD



Web and Email

• The class web site is http://www.cs.wisc.edu/~cs559-1– It is updated very frequently

– Lecture notes are put online before class, and updated after class

– Additional resources and links are provided

– Reading for future classes is listed

• The class mailing list is [email protected]– I assume that you check this email regularly

– All notices are sent out on the mailing list, including things not mentioned in class

– The mail goes to your cs class account, so make sure you check that or set up forwarding


Textbook and Reader

• Woo et. al., "OpenGL Programming Guide", Third Edition, Adison-Wesley, 1999– The definitive guide to OpenGL, and a reasonable description of

general real-time 3D graphics

• Class reader: Available at DOIT real soon now– A collection of papers, textbook chapters, and other documents

– Essential reading


Projects

• There will be three projects for the course, spread evenly through the semester

• Project 1: Image manipulation

• Project 2: Running a maze (probably)

• Project 3: Building a virtual theme park

• You must submit all three in order to pass the course


Homeworks

• There will be a homework every two weeks or so

• They are intended primarily to explore topics further and to prepare you for the exams

• They will be graded, but only the best five will count

• Some essential techniques will be presented only in homework– For example, an review of linear algebra


Grading (approximate)

• 45% Midterm and Final

• 45% Projects

• 10% Homework

• Everyone must write up their own homework, and write their own software, unless explicitly told otherwise


Lab Facilities

• Room B240 contains machines for use in this class

• They have high performance hardware and the software to make it work

• Students in 559 and 838 (animation) have priority in the lab, but it shouldn’t be a problem

• Don’t underestimate the benefits of working in a lab with your classmates


Software Infrastructure

• FLTK will be the user interface toolkit– Provides windows, buttons, menus, etc

– C++ class library, completely portable

– We are currently at version 1.11, available for free: www.fltk.org

• OpenGL will be the 3D rendering toolkit– Provides an API for drawing objects specified in 3D

– Included as part of Windows, available for Linux either as Mesa or hardware drivers (nvidia)

• Visual C++ 6.0 will be the programming environment for grading

• To be graded, your projects must compile under Visual C++ on the machines in room B240


C++

• This is probably the first, and only, class in which you must complete large software projects in C++

• There is a great deal of freedom in the projects, which requires that you do your own software design

• If you are not comfortable in C++, you will have to take action

• There are tutorials intended to teach you C++ assuming you know Java:– http://www.cs.wisc.edu/~hasti/cs368/CppTutorial/index.html

– These are intended for the course CS 368, but just do the tutorials

• The transition to C++ was one of the biggest issues for past CS559 studetns


Adding the Class

• To go on the waiting list, email [email protected] with your name, ID and major

• Do it again even if you have already send me email

• People who add in this manner will have to wait a couple of days for accounts


Programming Assignment 1

• Do the Visual C++ and FLTK demo off the class web page

• Will get you started with C++ and FLTK

• Do it NOW, don’t wait until the project comes up

• There will be another assignment in a week or so continuing your preparation for the first project

• Not graded. Questions during office hours or on the class mailing list


The Imaging Pipeline

• Consider taking a photo and viewing the result– Assume black and white, and a traditional film camera

• The film stores the image

• The camera is a device for imprinting the image on the film

• The image is viewed by a human

• We’ll look at these processes as an introduction to digital images


Photographs

• First photograph due to Niepce,

• First on record shown - 1822


Film

• Film samples (records) the intensity of light that strikes each point

• What is intensity?– The scientific term for that roughly corresponds to brightness

– It can be physically measured and there are many different units, such as lumens

• Real film is not perfect:– It has a finite dynamic range: it cannot simultaneously record very

dark and very bright regions - this is a big issue in photography

– It has finite resolution: if you blow it up large enough, you can see grains - this is rarely an issue in photography


Cameras

• A camera is a device for mediating the way light strikes film

• Lens lets light in while maintaining focus

• Aperture controls proportion of the light that gets to the film

• Shutter controls how long light is allowed to get to the film

Light in

Lens

Aperture

Shutter

Film


The Human Eye

• How do we see?– Light from the outside world excites

nerves in our retina

– The brain does the rest (not of concern in this class)

• To view a piece of film, we print it and look at the light that it reflects into our eye– Or, we shine light through a slide and see

what is transmitted


Images as Samples

• A photograph is a sample of the light that fell onto the film– Actually, it’s a very large set of samples, one for each point on the

film

• The camera controls precisely what is sampled– Which period of time is sampled

– Which region of space is sampled (which part of the light field)

– Which region of the electromagnetic spectrum is sampled

– Which range of intensity is sampled most accurately

• The idea of image as sample is central to many aspects of computer graphics


More on Film

• Film stores the samples of the light that fell onto it• Spatial continuity:

– In the real world, light tends to change smoothly over space– Film captures this smoothness quite well, with its high resolution

• Intensity continuity:– The real world contains a continuous range of intensities, from

bright to dark– Film can capture a sub-range very well, but not outside the range

• Temporal continuity:– In the real world, light tends to vary smoothly over time– Movie film captures a discrete set of images over time


Digital Images

• Computers work with discrete pieces of information• How do we digitize a continuous image?

– Break the continuous space into small areas, pixels– Use a single value for each pixel - the pixel value (no color, yet)– No longer continuous in space or intensity

• This process is fraught with danger, as we shall see

Continuous

Discrete

Pixels: Picture Elements

© university of wisconsin cs 559: computer graphics prof stephen chenney spring 2002 cs559-1

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