Chapter 1. Chapter 1. Computer Graphics 2006/2007 Chapter 1. Introduction 1

Transcription

1 Chapter 1 Chapter 1 Chapter 1. Introduction 1.1 Graphics and computer science 1.2 Advantages of interactive graphics 1.3 Computer graphics applications 1.4 Characteristic devices 1.5 Storage formats 1.6 The visualization process Computer Graphics 2006/2007 Chapter 1. Introduction 1

2 1.1 Graphics and Computer Science Prehistory Whirlwind: Defensive radar system (1951). Computer graphics origin. DAC-1: IBM & General Motors, 3D representation of a car. Advances in the 60 s Skechpad: Ivan Sutherland, considered as the father of computer gaphics. created an interactive drawing program.(1961) SpaceWar: Steve Russell (MIT) designed the first video-game on a DEC PDP-11. (1961) First animation shorts to simulate physical effects (gravity, movement, etc.) (1963) Computer Graphics 2006/2007 Chapter 1. Introduction 2

3 1.1 Graphics and Computer Science Sutherland (MIT) made up the first head-mounted display with stereoscopy vision (1966) First algorithm of hidden surfaces. by Catmull et al. at the Utah University. At the end of 60 s. The same team began to have interest in surface shading using color. Advances in the 70 s Introduction of computer graphics in television. Gouraud presented his famous polygonal surface smoothing method.(1971) Microprocessor on the market (1971) Atari was born in It is the computer game pioneer. Computer Graphics 2006/2007 Chapter 1. Introduction 3

4 1.1 Graphics and Computer Science First uses of CG (Computer Graphics) in movies. Newell at the University of Utah create the famous teapot, a classical benchmark for visualization algorithms. Texturing and Z-Buffer: Catmull s thesis in Phong developed his polygonal surface smoothing method (1974) Baum and Wozniak founded Apple in a garage. Gates founded Microsoft (1975). Lucasfilm created the computer graphics division with the best gurus of the moment (1979). Computer Graphics 2006/2007 Chapter 1. Introduction 4

5 1.1 Graphics and Computer Science Advances in the 80 s SIGGRAPH is the most important event in this field. Whitted published an article about ray tracing technique (1980) Carpenter, at Lucasfilm, developed the first rendering engine: REYES, the Renderman precursor.(1981) TRON film by Lisberger and Kushner at Disney (beginning of the 80 s) Massive sales of graphics terminals: IBM, Tektronix. The first ISO and ANSI standard for graphics libraries: GKS. IBM created the Personal Computer PC. Computer Graphics 2006/2007 Chapter 1. Introduction 5

6 1.1 Graphics and Computer Science Advances in the 90 s and nowadays: Operative system based on windows for PC (Windows 3.0 at 1990). 3D-Studio from Autodesk (1990). Massive use of computers to produce special effects: Terminator 2 (1991), Disney-Pixar (Toy Story, Bugs, Monsters, inc.), Forrest Gump, Jurassic Park, Lord of the Rings, Starwars episodes I, II and III etc. Internet success and 2D and 3D applications for the web. 3D graphics cards for PC (Voodoo, Nvidia Gforce etc.). Unstoppable 3D games evolution. Virtual Reality. A reality. Nowadays: a must for any application. Computer Graphics 2006/2007 Chapter 1. Introduction 6

7 1.2 Advantages of interactive graphics A better information recognition process It is possible to offer a higher information density We can show object relationships (interactivity) Color can be used Greater productivity (efficiency, use costs) Computer Graphics 2006/2007 Chapter 1. Introduction 7

8 1.3 Computer graphics applications Computer Aided Design CAD: (Computer Aided Design) Graphical tools that allow to design prototypes and evaluate them before producing them Most important areas Industrial design Architecture Electric circuits Integrated and printed circuits Most common technique Design based on constructive primitives, curved surfaces, etc. Other possibilities Virtual Reality, realistic presentation, constructive suggestions, design analysis, connection with manufacturing system (CAM Computer Aided Machinery) Computer Graphics 2006/2007 Chapter 1. Introduction 8

9 1.3 Computer graphics applications Presentation graphics Graphics as a support for reports and data presentation Most common areas 25 Economy Statistics 20 Mathematics 15 Management 10 Most common techniques 5 Line charts Pipe charts 0 Comidas 3D surfaces 30 Ene Transporte Alojamiento Ene Feb Mar Abr May Jun Feb Mar Abr May Jun Ene Feb Mar Abr May Jun Computer Graphics 2006/2007 Chapter 1. Introduction 9

10 1.3 Computer graphics applications Artistic field Artistic and commercial objectives Logo design Fine Arts Animations for advertising Techniques and software and software Programs like PhotoShop, CorelDraw, Freehand... Animation programs Image processing techniques rendering techniques Computer Graphics 2006/2007 Chapter 1. Introduction 10

11 1.3 Computer graphics applications Entertainment Areas Movies: (Tron, Toy Story, etc.) Television (transitions, headers, etc.) Computer games Techniques Animation Realistic visualization Special effects (Ex. morphing) Interactivity Computer Graphics 2006/2007 Chapter 1. Introduction 11

12 1.3 Computer graphics applications Simulation and training Areas Driving simulation Car driving or flight simulators Simulation of processes Industrial control panels simulation Training Components building and operation, medicine Teaching Children Techniques Real time, Interactivity Equipment Specific equipment (Ex. flight simulators) New techniques virtual reality Computer Graphics 2006/2007 Chapter 1. Introduction 12

13 1.3 Computer graphics applications Scientific and medical visualization Graphics visualization of huge amount of data Areas Medicine (Ex. resonnance) Engineering (Ex. strengths in a mechanism) Physics (Ex. Magnetic fields) Chemistry (Ex. Molecular interaction) Mathematics (Ex. equation solution) Topography and oceanography (Ex. Terrains and flows) Techniques Codification by color Level curves Volume visualization Computer Graphics 2006/2007 Chapter 1. Introduction 13

14 1.4 Characteristic devices: output Graphic terminal: monitor + controller + memory Connectors Focus Beam Grid vertical deflector horizontal deflector Ray phosphor CRT (Cathode Ray Tube ) characteristics The beam emits electrons (cathode). Ray intensity is controlled by the grid. The focus forces the electrons towards a convergence path. Deflectors force the ray to point at a specific screen point. The ray stuns over the phosphor. Phosphor emits lights. Phosphor emission declines very fast (refreshment required) Computer Gràfics per Graphics Computador 2006/2007 Chapter 1. Introduction 14

15 1.4 Characteristic devices: output Vector terminals Raster terminals Screen composed by pixels The ray traverses the screen from left to right and from top to bottom, lighting the pixels up Images is saved in memory (frame-buffer) The frame-buffer and the screen pixels are traversed simultaneously converting the color digital codes into ray intensities Considerations Resolution Sizes in pixels Aliasing Constant frame-rate Color possibility (n bits per pixel => 2 n colors) Differences between color modes of high density (16bits/pixel) and true color (24bits/pixel) and palette modes Computer Graphics 2006/2007 Chapter 1. Introduction 15

16 1.4 Characteristic devices: output Screen Ray Pixel Computer Graphics 2006/2007 Chapter 1. Introduction 16

17 1.4 Characteristic devices: output 1 Record 1 CRT Raster Frame Buffer Raster CRT graphic device with Frame Buffer W/B of one bit plane Records Blue Green Red CRT Raster Frame Buffer Frame Buffer of simple color Computer Graphics 2006/2007 Chapter 1. Introduction 17

18 1.4 Characteristic devices: output Liquid Crystal Displays (LCD) Liquid crystals are substances that have properties of liquid and solids When light goes through them, the LC forces it to follow the alignment of its molecules If an electric source is applied to them, its molecular alignment changes and, therefore, the way the light goes through them Displays are formed as LC panels (between two polarized filters) and a back light (normally a cold cathode) Most common technologies: DSTN (dual-scan twisted nematic) and TFT (thin film transistor) TFT: an extra matrix of transistors (1 per color, RGB, of each pixel) and allows better performance (avoiding ghosting), brightness and contrast Advantages over CRT: lower frame-rates (refreshment useful just for animation), less energy consumption, less space Disadvantages: fixed resolutions, less vision angles. Other technologies: plasma (high voltages to low pressure gases (xenon) that forces the gas to change from gas states to plasma generating light) Computer Graphics 2006/2007 Chapter 1. Introduction 18

19 1.4 Characteristic devices: output Related with virtual reality and immersive environments: glasses and stereoscopic helmets, caves. Printing devices: printers and plotters. Computer Graphics 2006/2007 Chapter 1. Introduction 19

20 1.4 Characteristic devices: input Keyboard, mouse Trackball, digital tablet, optical pen 3D digitizers, joysticks (2D and 3D) 3D gloves, motion capture systems Specific systems (flight and car driving simulators etc.) Computer Graphics 2006/2007 Chapter 1. Introduction 20

21 2.5 Storage formats Representation Vectors Bitmap Definitions Bitmap representation Image is decomposed into pixels. The value of each one is saved individually. It s easy to implement and works, with some limitations (e.g. aliasing), with any type of image Vector based representation Image is represented by a set of geometrical shapes (lines, circles, curves etc.) The parameters that define the geometric shapes are saved Applications Bitmaps: Complex color variations, like real photographs or images that are difficult to be vectorized. Vectors: Technical draws, CAD, imagery with simple shapes and coloring. Computer Graphics 2006/2007 Chapter 1. Introduction 21

22 2.5 Storage formats BITMAPS VECTORS Advantages Disadvantages Any type of image can be saved Programming is generally simpler Lot of memory required Huge volume of data Few flexibility Fixed resolution More efficient and flexible in many applications Parts of a scene can be manipulated Scale changes do not affect to resolution and quality There are limits or important difficulties in order to represent some images Computer Graphics 2006/2007 Chapter 1. Introduction 22

23 1.6 The visualization process Graphics applications = Hardware (graphics devices + computer) + Software (model + program + graphic library) Model: object data Geometry, properties (color, material, texture, etc.), hierarchical structures, etc. Kernel or application: works with model information Add, modify and remove data, user s actions management Graphic engine or library: interface between application and hardware Output: data visualization Input: user s interaction Model Application graphic library Computer Graphics 2006/2007 Chapter 1. Introduction 23

24 1.6 The visualization process Image synthesis process (visualization process) is the set of 3D and 2D operations undertaken over a computer data model that generate a graphic representation of the model in a physical display Computer Graphics 2006/2007 Chapter 1. Introduction 24

25 1.6 The visualization process 3D graphic pipeline Scene traversal Modeling transformation Viewing transformation Clipping Hidden faces removal Projection Device transformation Lighting Rasterization Screen Computer Graphics 2006/2007 Chapter 1. Introduction 25

26 1.6 El proceso de visualización 2D graphics pipeline decomposition in drawing primitives clipping coordenate system transformation geometric model rasterization Computer Graphics 2006/2007 Chapter 1. Introduction 26