b a c kn e x t h o m e CSCI 346 Chapter 1 Graphics Systems and Models

b a c kn e x t h o m e Agenda Homework that is due Wednesday? Chapter 1

b a c kn e x t h o m e Chapter 1 Computer Graphics –producing pictures or images using a computer 40 years ago –drawing lines on a cathode ray tube Today –produce images indistinguishable from photos –produce “realistic” and animated dinosaurs –produce 3D worlds

b a c kn e x t h o m e Computer Graphics Applications Display of Information Design Simulation User Interfaces

b a c kn e x t h o m e Display of Information Maps –GIS –Spatial Resource Planning (SRP) – Medicine –MRI and _images/brain-fmri.jpg _images/brain-fmri.jpg –“seeing the unseen” –Visual Human Project –biology –electrophysiology –mathmatics

b a c kn e x t h o m e Geographic Information System (GIS) Stores information about the world as a collection of thematic layers that can be linked together by geography. Uses include –tracking delivery vehicles, –planning applications –modeling global atmospheric circulation.

b a c kn e x t h o m e GIS

b a c kn e x t h o m e Spatial Resource Planning Spatially-referenced data within engineering, operations and distribution network management Analogous to what Enterprise Resource Planning (ERP) solutions do for data held in accounting, human resources, procurement and project management systems,

b a c kn e x t h o m e Magnetic Resonance Imaging (MRI) and fMRI Uses magnetism and radio waves to produce images

b a c kn e x t h o m e Ultrasound or CT Scan Images are produced by very high frequency sound waves or x-rays

b a c kn e x t h o m e Scientific Visualization Visual Human Project “Visible Man Thighs” from GE Research and Development (Bill Lorenson) from GE Research and Development (Bill Lorenson)

b a c kn e x t h o m e Scientific Visualization Electrophysiology Computed Potential Distribution on the Cardiac Surface during reentry: Spiral Tip Meandering, an arrhythmia model

b a c kn e x t h o m e Design "the evaluation of alternative solutions and the specification of a solution” CAD / CAM (inc rapid prototyping) VLSI design generate a possible design, test, use solution as a basis for other solution

b a c kn e x t h o m e Simulation Simulators – surgeryhttp://www- kismet.iai.fzk.de/VRTRAIN/phD_mai n.html, flighthttp://www- kismet.iai.fzk.de/VRTRAIN/phD_mai n.html Games Educational (edutainment) software Virtual Reality

b a c kn e x t h o m e User Interfaces Interaction with computers –WindowsWindows –Icons –Menus –Pointing device

b a c kn e x t h o m e Graphics System Processor Memory Frame buffer Output devices Input devices

b a c kn e x t h o m e Processor Simple system -- one processor handling –Normal processing –Graphics processing  Rasterization  Scan conversion

b a c kn e x t h o m e Pixels and the Frame Buffer Picture or image is produced as a array (raster) of picture elements (pixels) Pixels are stored in part of memory called the frame buffer

b a c kn e x t h o m e Frame Buffer depth -- number of bits used for each pixel –full color systems  true color systems  RGB color systems  24 or more bits per pixel resolution -- number of pixels in the frame buffer

b a c kn e x t h o m e Output Devices Dominant type of display is the CRT (cathode ray tube) CRT emits light for a short time -- a few milliseconds. For a human to see a steady image the path must be retraced or refreshed at least 50x/sec how are pixels displayed

b a c kn e x t h o m e How Are Pixels Displayed? Noninterlaced –displayed row by row Interlaced –Displayed every other row –50-75X/second (50-75Hertz) –60Hz display refreshes the entire screen 30x/sec –Commercial TV

b a c kn e x t h o m e Color CRTs 3 phosphors arranged in (sometimes triangular) triads shadow mask CRT screen with small holes ensures only one phosphor is excited

b a c kn e x t h o m e Other Output Devices - Raster Liquid Crystal Displays (LCD) Plasma Displays LED Displays Printers

b a c kn e x t h o m e Input Devices Keyboard Mouse Lightpen Joystick Data tablet

b a c kn e x t h o m e Ways to Read an Input Device Sampling –What is its input right now ? Event-based –Wait until the user does something

b a c kn e x t h o m e 3D Input Devices 3D Input devices Read a 3D position Returns 3 numbers to the program: an (x,y,z) triple Examples: digitizer, spaceball, glove

b a c kn e x t h o m e Objects and Viewers 3d world Object is a constant Viewer forms the image –human viewing system - back of eye –camera - film plane –different viewers see the same object differently

b a c kn e x t h o m e Objects and Viewers Pinhole Camera

b a c kn e x t h o m e Light and Images no light -- can't see anything simplest scenario one light source –light from the source strikes various surfaces of the objects –portion is reflected and goes thru the lens to the camera –many variations based on the surface characteristics of the object

b a c kn e x t h o m e Light a form of electromagnetic radiation the light or visible spectrum is a subset of the electromagnetic spectrum (includes radio waves) light travels in straight lines from the source to the object a theoretical point source would have monochromatic light emanating equally in all directions

b a c kn e x t h o m e Ray Tracing simple concept computationally expensive scene –viewer –objects –and a light source –a ray: semi infinite line emanates from the point source and travels to infinity in some direction

b a c kn e x t h o m e Ray Tracing

b a c kn e x t h o m e Ray Tracing Tracing rays from the light source to the eye. Lots of rays are wasted because they never reach the eye.

b a c kn e x t h o m e Ray Tracing Trace a new ray toward the light source.

b a c kn e x t h o m e Ray Tracing

b a c kn e x t h o m e Ray Tracing - Recursive

b a c kn e x t h o m e Ray Tracing rays travel –directly to the viewer –out to infinity –strike an object and  mirror - reflect  diffuse surface - scatter  transparent - light passes thru the object but is changed maybe refracted or bent

b a c kn e x t h o m e Ray Tracing modeled on the real world not fast -- in fact so slow that for real time or even semi real time graphics we need to look for another option

b a c kn e x t h o m e Homework for this week Reading Chapter 2 Homework 1 - Due 9:00 AM 01/24/07