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Graphic Systems, Lighting, and Models

Graphic Systems, Lighting, and Models. Why do we need graphics?. To convey information Simulation User interfaces. A Graphics System. Input devices Processor Memory Frame buffer Output devices. The Frame Buffer. Is an array – the raster – that holds graphics related information

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Graphic Systems, Lighting, and Models

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  1. Graphic Systems, Lighting, and Models

  2. Why do we need graphics? • To convey information • Simulation • User interfaces

  3. A Graphics System • Input devices • Processor • Memory • Frame buffer • Output devices

  4. The Frame Buffer • Is an array – the raster – that holds graphics related information • Mostly, it holds pixels • Converting geometric entities to pixel information is called rasterization • Each pixel in a picture requires color data • The number of bits used is called its depth • The depth determines how many different colors an image can have

  5. 24-bit (true color)

  6. 8-bit (256 colors)

  7. 4-bit (16 colors)

  8. 3-bit (8 colors)

  9. 8-bit Grayscale

  10. Color Pallet • Non-true color images store the color values in pallets • Pallets are an array of colors stored, usually, at the beginning of an image file • The color information of a particular pixel is stored as an index reference to the pallet

  11. Example pallet

  12. True Color • 24-bit images • use 3, 8-bit segments to encode the three primaries: Red, green, and blue (RGB) • Each 8-bit segment can, therefore, hold 256 shades of that color • This results in a possible 16,777,216 different colors

  13. Output Devices • The first, and still most widely used, is the cathode-ray tube (CRT)

  14. More on CRTs

  15. LCD Displays

  16. The human element • If a computer draws a picture and there is no one there to see it, was it pretty? • Was it even a picture? The purpose of graphics is to be viewed by humans

  17. The human visual system • Light enters the eye through the lens and cornea • The iris opens and closes to regulate the amount of light coming in

  18. The human visual system • An inverted 2D image is produced on the retina • Sensor apparatuses called rods and cones detect features of the light that strike them

  19. The human visual system • The rods and cones then send their signal down the optic nerve to the visual cortex of the brain

  20. The human visual system • We can see electromagnetic energy in the frequency range of 350 to 780 nm

  21. The human visual system • The sizes of the rods and cones along with properties of the lens and cornea determine our visual resolution • Resolution is the measure of how close we can place two points and still recognize that there are two distinct points

  22. The human visual system • There are three different types of cones that respond to different wave lengths of light

  23. The human visual system • The intensity of an image is the physical amount of light • The brightness of an image is the perceived amount of light

  24. We live in a 3D world • Because of binocular vision

  25. Ray tracing • A point source (of light) is the engine

  26. Synthetic-Camera Model • If we imagine a camera taking a picture of our virtual scene, we must consider many different aspects of what that camera might see

  27. Next class Beginnings of graphics programming

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