CS 559: Computer Graphics

1. CS 559: Computer Graphics Prof Stephen Chenney Spring 2002 http://www.cs.wisc.edu/~cs559-1 © University of Wisconsin

2. Today • Course overview and information • Getting started on images • Programming assignment 1 © University of Wisconsin

3. 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, … © University of Wisconsin

4. Is 2D Graphics Important? Sprites in games: Images are built by overlaying characters and objects on a background Compositing in movies: images are created in layers, and then combined © University of Wisconsin

5. 3D is Sometimes Essential Augmented Reality, from Eric Grimson’s research group at MIT Virtual Reality, the Iowa Driving Simulator © University of Wisconsin

6. 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. © University of Wisconsin

7. 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, … © University of Wisconsin

8. Professor Stephen Chenney Room 6387 Office Hours Tues 2-3, Thurs 10-11 schenney@cs.wisc.edu TA: Matt Anderson Office Hour TBD manderso@cs.wisc.edu TA: Eric McDaniel Office Hour TBD chate@cs.wisc.edu People © University of Wisconsin

9. 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 cs559-1list@cs.wisc.edu • 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 © University of Wisconsin

10. 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 © University of Wisconsin

11. 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 mustsubmit all three in order to pass the course © University of Wisconsin

12. 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 © University of Wisconsin

13. 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 © University of Wisconsin

14. 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 © University of Wisconsin

15. 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 © University of Wisconsin

16. 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 © University of Wisconsin

17. Adding the Class • To go on the waiting list, email schenney@cs.wisc.edu 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 © University of Wisconsin

18. 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 © University of Wisconsin

19. 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 © University of Wisconsin

20. First photograph due to Niepce, First on record shown - 1822 Photographs © University of Wisconsin

21. 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 © University of Wisconsin

22. Cameras Light in • 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 Lens Aperture Shutter Film © University of Wisconsin

23. 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 © University of Wisconsin

24. 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 © University of Wisconsin

25. 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 © University of Wisconsin

26. 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