香港大学计算机图形学课件Chapter1

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Interactive Input Devices
Keyboard Mouse Tablet/stylus
consist of a flat drawing board and a pen electromagnetic high resolution
Joystick
provides true 3-d scenes and interactions
Head-mounted display (HMD) A system for tracking the position of HMD Data glove
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Computer-Aided-Design interactively design and modify objects
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A graphics system with a display processor
(Section 4.3 of Foley, van Dam)
Video Controller Frame buffer
Monitor
CPU
Display processor
System bus
System memory
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Synthesizing images
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Virtual idol (Reiko Arisugawa)
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Ray tracing images
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Animation films
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Games
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Flight simulators
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Virtual reality
(0,0.7)
Reading Assignment
Interactive Com. Gra. Chapters 1 and 2
(-0.7,-0.7) (0.7,-0.7)
OpenGL: A Primer Chapters 1 and 2
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void display() { glClear( GL_COLOR_BUFFER_BIT); // Clear the frame buffer glColor3f( 0.0, 1.0, 0.0); glBegin( GL_POLYGON); glVertex2f( -0.7, -0.7); glVertex2f( 0.7, -0.7); glVertex2f( 0, 0.7); glEnd(); // Set current color to green // Draw the triangle
The beam moves regularly in the trails shown on the left.
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The picture seen on the screen is controlled by the changes of intensity and color along the movement of the beam
Polarizers
Light passes through
Light is blocked
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References: /sc/library/lcd_e/s2_1_1e.htm
Architecture of a simple display system
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Computer Art
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Cathode-ray tube display (CRT)
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The focus, position and movement of the beam are controlled by the electric fields generated by the deflection plates When the beam hits the phosphor on the screen, the phosphor lights up but its intensity decays very fast. Nonetheless, the image retains in the retinas of our eyes for about 1/20 sec.
Color CRT (3 guns: Red, Green and Blue)
1 pixel
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Liquid Crystal Display (LCD)
The basic unit is a small device that twist the polarization of light 90o. But the twisting can be turned off when a voltage is applied. By adding two polarized planes with orthogonal orientations in both ends, this device can serve as a switch that controls whether light can pass through or not.
Ink-Jet printers
spray electrically charged ink on paper ink stream is deflected by electric field multiple jets of different color ink can shot simultaneously for producing color drawings
Ordinary X-ray image
Cross section X-ray image (tomography)
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Magnetic resonance tomography images
Ultrasound images
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Graphical user interface
icons, frames, labels, fields, text-area, buttons, pop-up manuals,...
Display card
cpu
Frame Buffer (Raster)
Video Controller
Monitor
Frame buffer size For XVGA, altogether 31024768 2.4 Mbytes Since there are other buffers and overhead, a typical display card may contains 4 to 32 Mbytes RAM. Video controller cycles through the frame buffer to refresh the screen 30 - 120 times per seconds.
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Curves
0.6 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97
Surfaces
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Weather charts
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2-d images from volume data
Chapter 1 Introduction to Computer Graphics
“One picture is better than a thousand words” Vision is the most important sense of humans
A significant portion of a human brain processes visual information Our vision is by far better than most of other animals’
the rate of cursor movement depends on the displacement of the stick
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Scanners Touch-screen monitors
electronic/optical allow screen positions to be selected low resolution
Peripheral devices
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Printers
Laser printers
use laser beam to create a charge distribution on a drum coated with a photoelectric material. Toner is applied to the drum and then transferred to paper. To produce a color copy, the process is repeated three times for red, green and blue colors.
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Overview
Applications
Output devices: CRT, LCD
Interactive input devices: keyboard, mouse, tablet/stylus, joysticks, Touch-screen monitors Computer graphics systems Introduction to OpenGL
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3D handheld laser scanning digitizer
Long Range Laser Scanning
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Motion Tracking sensors
Motion
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OpenGL programming
OpenGL ( gl ) is a common graphics library which provides functions for drawings and interactive input. OpenGL is accessible via C++ programs The Visual C++ platform is used for program development in this course A function that draws a green triangle Green Triangle