09/03/02© 2002 University of Wisconsin CS 559: Computer Graphics Prof Stephen Chenney Fall

09/03/02© 2002 University of Wisconsin Today Course overview and information Getting started on images Programming assignment 1 (off class home page)

09/03/02© 2002 University of Wisconsin 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, …

09/03/02© 2002 University of Wisconsin Is 2D Graphics Important? Compositing in movies: images are created in layers, and then combined Sprites in games: Images are built by overlaying characters and objects on a background

09/03/02© 2002 University of Wisconsin Virtual Reality Iowa Driving Simulator Augmented Reality W. Eric L.Grimson at MIT vision/surgery/surgical_navigation.html 3D is Sometimes Essential

09/03/02© 2002 University of Wisconsin 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.

09/03/02© 2002 University of Wisconsin 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, …

09/03/02© 2002 University of Wisconsin People Prof. Stephen Chenney –Room 6387 –Office Hours Tues 2-3, Thurs TA: Matt Allen –Office Hour TBD TA: David Gekiere –Office hours TBD Send all class to It is read by both Prof Chenney and the TAs and gets the fastest response

09/03/02© 2002 University of Wisconsin Web and The class web site is –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 –I assume that you check this 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

09/03/02© 2002 University of Wisconsin Textbooks and Reader Peter Shirley, “Fundamentals of Computer Graphics”, A.K. Peters, 2002 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 –A collection of papers, textbook chapters, and other documents –Some essential material not contained in the textbook

09/03/02© 2002 University of Wisconsin Projects There will be three projects for the course, spread evenly through the semester Project 1: Image editing Project 2: Running a maze Project 3: Building a virtual theme park You must submit all three in order to pass the course

09/03/02© 2002 University of Wisconsin 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

09/03/02© 2002 University of Wisconsin Grading (approximate) 45% Midterm and Final 45% Projects 10% Homework Everyone must write up their own homework For the projects, you have the option of working in pairs

09/03/02© 2002 University of Wisconsin 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 CS 559 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 –For instance, the blackboards frequently display useful hints But they also sometimes have incorrect information!!

09/03/02© 2002 University of Wisconsin Software Infrastructure FLTK will be the user interface toolkit –Provides windows, buttons, menus, etc –C++ class library, completely portable –We are currently at version 1.1.0rc6, available for free: 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 (software) or hardware drivers Visual C will be the programming environment for grading To be graded, your projects must compile under Visual C++ on the machines in room B240

09/03/02© 2002 University of Wisconsin C++ This is probably the first, and only, class in which you must complete large software projects in C++ without step by step instructions 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: – –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 students

09/03/02© 2002 University of Wisconsin Adding the Class To go on the waiting list, with your name, ID and Do it again even if you have already send me People who add in this manner will have to wait a couple of days for accounts

09/03/02© 2002 University of Wisconsin 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

09/03/02© 2002 University of Wisconsin Images Information presented in a flat (2D) format to be examined visually We are familiar with many forms of image: –Photographs –Paintings –Sketches –Television –Computer screens Each form has its own way of obtaining and storing the information content

09/03/02© 2002 University of Wisconsin Digital Images Images can be stored on a computer in one of many forms There are some conflicting goals: –The storage cost should be minimized –The amount of information stored should be maximized –It should be easy to perform editing operations –Tracking copyrights may be important There are two abstract types of digital images: Raster images and Vector images

09/03/02© 2002 University of Wisconsin Raster Images A raster is a regular grid of pixels (picture elements) Raster image formats store the intensity (brightness) and color information at each pixel –Simplest is to use a 2D array of pixel values –Some formats store the pixel information in very different ways A 6x3 image Aspect ratio is width/height, 2

09/03/02© 2002 University of Wisconsin Vector Images Store images as collections of geometric primitives –E.g. Lines, polygons, circles, … Called vector images for historical reasons Postscript (PDF) is the most famous vector image format It is possible to go from a vector image to a raster image It is very hard to go the other way

09/03/02© 2002 University of Wisconsin Obtaining Digital Images What are some methods for obtaining a digital image?

09/03/02© 2002 University of Wisconsin Obtaining Digital Images What are some methods for obtaining a digital image? –Digital camera –Scanning another image –Medical scanning –Editing existing digital images –Paint or drawing programs –Created from abstract data (e.g. math function plot) –Rendered from a scene description –…

09/03/02© 2002 University of Wisconsin Displaying Images Display is not the same as storage –A monitor displays an image, but does not store it –The same image may look different on different monitors Typically, the display is taken into account when creating images, but not always Different display techniques have very different properties What are some common display techniques?

09/03/02© 2002 University of Wisconsin Displaying Images What are some common display techniques? –Cathode Ray Tube (CRT): Computer monitor / Television –Liquid Crystal Display (LCDs) –Printing: many variations –Vector displays –Holographic displays –Plasma displays –…

09/03/02© 2002 University of Wisconsin Trade-Offs Which is preferred: Raster or Vector? –For display on an LCD? –For display on a plotter (a printer that draws lines with pens)? –For images from digital cameras? –For CAD (Computer Aided Design)? –For high-quality text? Which is easier to: –Resize? –Rotate? –Crop?

09/03/02© 2002 University of Wisconsin Trade-Offs Which is preferred: Raster or Vector? –For display on an LCD? Raster –For display on a plotter (a printer that draws lines with pens)? Vector –For images from digital cameras? Raster –For CAD (Computer Aided Design)? Vector –For high-quality text? Vector Which is easier to: –Resize? Vector –Rotate? Vector –Crop? Raster

09/03/02© 2002 University of Wisconsin Next Time We focus on raster images Some human perception stuff (always fun)