CS-460/560, Wk1a Spring, 2000 R. Eckert An Introduction to Computer Graphics Computer Graphics-- Using a computer to generate visual images Motivation-- Human visual channel highly developed Visual channel very efficient for communicating complex ideas Definition of Computer Graphics: Creation, storage, manipulation, and display of models of objects (real or imagined) using the computer. Interactive Computer Graphics: User dynamically controls displayed image attributes by means of interactive input devices. Image Processing-- Related to computer graphics Reconstruction of objects from their images Computer Graphics--Synthesis of images (Objects ---> Images) Image Processing--analysis of images (Images ---> Objects) Image Processing subfields-- image enhancement computer vision pattern recognition (AI important) Two Phases of Computer Graphics-- 1. Modeling Mathematical representations of objects/scenes 2. Rendering Production of an image from a model Features of computer graphics models- Output primitives: building blocks Data structures: how primitives relate to each other Levels of Complexity of Computer Graphics-- Depends on objects/scenes to be modeled and rendered a. 2-D Line Drawings (charts, graphs); drawing programs Need algorithms to efficiently draw lines, circles, text, etc.
Example: b. 2-D colored images (colored objects); painting programs Need efficient area fill algorithms Example: c. 3-D line drawings (wire frames) Need efficient algorithms to project from 3-D to 2-D Example: d. 3-D line drawings with hidden lines removed Need efficient hidden line removal algorithms Example: Note: all hidden lines in each object have been removed, but lines in objects hidden by other object have not been removed. e. 3-D colored images Need algorithms for hidden surface removal, color, shading Examples: Also all hidden surfaces have removed. All surfaces have been "flat shaded." Plane surfaces have been flat shaded. Cylinders & condes have been "Gouroud smooth shaded." The sphere has been "Phong smooth shaded"--note specular highlight. f. 3-D photorealistic images Need models that take into account materials properties, lighting, reflection, transparency, shadows; The physical interaction of light with material (physics) Modeling techniques for complex (natural) objects (e.g., fractals) Examples: A ray traced scene with transparency, reflection, & texture mapping. A scene with fractal mountains & L-system generated plants. g. Animation at all levels Make things move realistically The above image is one frame in a robot runner animation. Each frame was generated with a ray tracing program. SOME APPLICATIONS OF COMPUTER GRAPHICS: Data Presentation (statistics, business, scientific, demographics...) CAD, CAM, CIM Painting/Drawing systems TV commercials Entertainment Video Games Cartography Computer Art Motion Picture Industry (animation, special effects, etc.) Desktop publishing Architectural Design Simulation of Reality Flight simulators Ground vehicle simulators Arcade games Virtual reality devices Scientific Simulation/Visualization Use graphics to make sense of vast amounts of scientific data Hypermedia Integration of broadcasting, computing, publishing Education Process Control CASE Image Processing/Enhancement Medicine Computed Tomography X-ray, ultrasound, NMR, PET: --> 3-D images of human anatomy GUIs World Wide Web Development VRML New Stuff--can't even be imagined Computer Graphics-- A huge, fast-moving, exciting field that integrates the best of art and science Needs new Renaissance men & women Bright and analytic enough to understand the science & math Sensitive and creative enough to do the art Both left and right sides of the brain required! BRIEF HISTORY OF COMPUTER GRAPHICS Early 50s--MIT Whirlwind Computer First computer-driven CRT Middle 50s--SAGE Air Defense System Selection of targets with light pen First interactive graphics Early 60s--Ivan Sutherland (father of computer graphics) Ph.D. Thesis: SKETCHPAD Proposed 1st complete model for interactive graphics Identified basic data structures Discovered important algorithms Many of his ideas still in use Middle 60s--GM's Digigraphic Design System Beginning of CAD Costly hardware, Hard-to-write programs, Non-portable software Late 60s--Tektronix Direct View Storage Tube First inexpensive graphics display device Early 70s--First microprocessors --> first microcomputers inexpensive primitive graphics capability Late 70s--First graphics software standard (CORE--1977) First attempt at portable graphic software 1980s--Proliferation of micros with extensive graphics capabilities Introduction of first Work Stations (graphics engines) Appearance of graphics standards with increased capabilities GKS (1984), GKS-3D (1988), PHIGS (1988) Microcomputer GUIs (Macintosh, Windows) 1990s--Graphics engines (algorithms implemented in hardware) Fast, powerful, cheap Multimedia systems Windows-95, Windows-NT, X Windows, PEX GL, OpenGL industry standard graphics libraries Microsoft Direct-X