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CSCI 346

Chapter 1 Graphics Systems and Models CSCI 346 Agenda Homework that is due Wednesday? Chapter 1 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

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CSCI 346

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  1. Chapter 1 Graphics Systems and Models CSCI 346

  2. Agenda Homework that is due Wednesday? Chapter 1

  3. 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

  4. Computer Graphics Applications Display of Information Design Simulation User Interfaces

  5. Display of Information Maps GIS Spatial Resource Planning (SRP) http://earth.google.com/ Medicine MRI and http://mednews.stanford.edu/stanmed/2005fall/story_images/brain-fmri.jpg “seeing the unseen” Visual Human Project biology electrophysiology mathmatics

  6. 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.

  7. GIS

  8. 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,

  9. Magnetic Resonance Imaging (MRI) and fMRI Uses magnetism and radio waves to produce images

  10. Ultrasound or CT Scan Images are produced by very high frequency sound waves or x-rays

  11. Scientific VisualizationVisual Human Project “Visible Man Thighs” from GE Research and Development (Bill Lorenson)

  12. Scientific VisualizationElectrophysiology Computed Potential Distribution on the Cardiac Surface during reentry: Spiral Tip Meandering, an arrhythmia model

  13. 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

  14. Simulation Simulators – surgeryhttp://www-kismet.iai.fzk.de/VRTRAIN/phD_main.html, flight Games Educational (edutainment) software Virtual Reality

  15. User Interfaces Interaction with computers Windows Icons Menus Pointing device

  16. Graphics System Processor Memory Frame buffer Output devices Input devices

  17. Processor Simple system -- one processor handling Normal processing Graphics processing Rasterization Scan conversion

  18. 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

  19. 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

  20. 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/sechow are pixels displayed

  21. 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

  22. Color CRTs 3 phosphors arranged in (sometimes triangular) triads shadow mask CRT screen with small holes ensures only one phosphor is excited

  23. Other Output Devices - Raster Liquid Crystal Displays (LCD) Plasma Displays LED Displays Printers

  24. Input Devices Keyboard Mouse Lightpen Joystick Data tablet

  25. Ways to Read an Input Device Sampling What is its input right now ? Event-based Wait until the user does something

  26. 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

  27. Objects and Viewers3d 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

  28. Objects and ViewersPinhole Camera

  29. 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

  30. 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

  31. 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

  32. Ray Tracing

  33. Ray Tracing • Tracing rays from the light source to the eye. • Lots of rays are wasted because they never reach the eye.

  34. Ray Tracing • Trace a new ray toward the light source.

  35. Ray Tracing

  36. Ray Tracing - Recursive

  37. 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

  38. 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

  39. Homework for this week Reading Chapter 2 Homework 1 - Due 9:00 AM 01/24/07

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