COMPUTER GRAPHICS CISC440 CISC640 Instructor: Prof. Chandra Kambhamettu TA: Mani Thomas Intructor Office Hours: Wed. 2-4pm Smith403 ppt slides design credits: Chaitra Murthy (MS, UD) Figures: Hearn and Baker, U of Illinois
INTRODUCTION • COMPUTER GRAPHICS • IMAGE PROCESSING • COMPUTER VISION >>>Graphics Timeline
COMPUTER GRAPHICS • Computer graphics is concerned with all aspects of producing images using a computer • It concerns with the pictorial synthesis of real or imaginary objects from their computer based models • BACK
IMAGE PROCESSING Image processing is the converse process of computer graphics. Image processing and Understanding areas concentrate on analysis and reconstruction of 2D or 3D objects from their pictures • BACK
COMPUTER VISION Computer vision further more extends research into understanding images. It is the construction of explicit, meaningful descriptions of physical objects from images. • BACK
GRAPHICS TIMELINE • THEN • The field humbly began 45 years ago with a few lines on a cathode ray tube. • Until early 1980’s it was a small specialized field due to expensive hardware and software (application programs)
GRAPHICS TIMELINE Now • We can generate images almost indistinguishable from photographs • Interactive….highly interactive!! In present times user controls the contents, structure and appearance of objects by using various input devices
GRAPHICS TIMELINE Now (continued) • Direct manipulation is in heavy use • We can make feature-length movies entirely by computer • On the whole, the development of computer graphics is driven both by the needs of the user community and by the advances in hardware and software
POPULARITY why is it so popular -A picture is worth a 10000 words!!!!! It provides the most natural means of communicating with a computer, since our perception abilities arebetter with pictures than with words It is one of the rare fields that has many commercial interests as there are research interests (Thanks to Hollywood!!)
APPLICATIONS Computer graphics is so much in demand because of its limitless variety of applications • Display Of Information Medium to convey information • Design Many applications exist in engineering and architecture (CAD,VLSI) • Simulation Graphical flight simulators, games, commercials and educational software • User Interfaces Visual paradigms in user interaction: windows, icons, menus etc. Virtual Reality Applications
Wooden Mirror (D. Rozin, NYU) • Sitting • Movie • Hand-still The wooden mirror has 830 pieces of wood each about 40 mm square arranged into an octagon of 35 x 29 . Each piece of wood is connected to a servo motor that can tilt it about 30º up and down. The whole piece is lit from above with a few spot lights, in a way that when the pieces are tilted upwards they become brighter, and when they tilt downwards they become darker. The servo motors can position each piece in 255 positions theoretically yielding 255 gray levels per piece. In the center of the Mirror a tiny video camera is concealed.
Image Creation • Camera is used to take an image, stored on the film. • Film records sample of intensity that hits each point • Intensity is brightness of a point (amount of light reflected off the point), usually measured in lumens. • Intensity is discretized to pixel values (continuous -> discrete)
Images.. CAMERA: • Light rays come through lens in the camera and hits the film. • Proportion of light that hits the film is controlled by the aperture (adjusted in combination with the focal length). • Time duration (to keep the door open for light to come-in) is controlled by shutter speed. Us: • Light from the outside world excites nerves in our retina and brain understands the stereo images of our retina.
Discrete vs. Continuous worlds • Computers are in discrete world, so we break the continuous domain (time and space) into discrete domain. • Animation: 24 to 30 frames per second • Image: small dots making up a matrix for the display. The small dots are Gaussian, called pixels. • Value given to each pixel is called intensity.
SUMMARY • Introduction • Graphics Timeline • Popularity Of Computer Graphics • Applications Of Computer Graphics • Short notes on Images