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RAIN WATER HARVESTING
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INTRODUCTION -OPENGL
Computer graphics is concerned with all aspects of producing pictures or images using a computer. The field began humbly almost 50 years ago, with the display of a few lines on a cathode-ray-tube (CRT). Now we can create images by computer that are indistinguishable from photographs of real objects. The software used is OpenGL.
Open graphics library is a standard specification defining a cross platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex 3D scenes and simple primitives.
OpenGL is widely used in CAD,virtual reality, scientific visualization, information visualization, flight simulation and video games. OpenGL specifies a set of commands or immediately executes functions. Each command directs a drawing action or causes a special effect. A list of these commands can be created by repetitive effects.
OpenGL is independent of windowing characteristics of each operating system. But provides a special GLU routines for each operating system that enables OpenGL to work with th system’s windowing environment. OpenGL comes with a large number of building capabilities. These include hidden surface removal, alpha blending, antialiasing, texture mapping, pixel operation, viewing, modeling transformation and atmospheric effects.
Functions in the OpenGL library have names that begin with the letters gl and are stored in a library usually referred to as GL.
The second is the OpenGL Utility Library (GLU). This library uses only GL functions but contains code for creating common objects and simplifying viewing. All functions in GLU can be created from the core GL library.
To interface with the window system and to get input from external devices into our programs, we need at least one more library. Rather than using a different library for each system, we use a readily available library called the OpenGL Utility Toolkit (GLUT), which provides the minimum functionality that should be expected in any modern windowing system.OpenGL makes use of macros to increase code readability.
OpenGL supports two types of primitives: geometric primitives and raster primitives.Geometric primitives are specified in the problem domain and includes points,line segments, polygons,curves,and surfaces They exist in a 2Dor 2D space, they can be manipulated by operations such as rotation and translation. Raster primitives, such as arrays of pixels, lack geometric properties and cannot be manipulated in space.
Graphics systems and models:
Computer graphics started with the display of data on hardcopy plotters and cathode ray tube (CRT) screens soon after the introduction of computers themselves. It has grown to include the creation, storage, and manipulation of models and images of objects. These models come from a diverse and expanding set of fields, and include physical, mathematical, engineering, architectural, and even conceptual structures, natural phenomena, and so on. Computer graphics today is largely interactive .The user controls the contents, structure, and appearance of objects and of their displayed images by using input device, such as a keyboard, mouse, or touch-sensitive panel on the screen. Because of the close relationship between the input devices and the display, the handling of such devices is included in the study of computer graphics.
Until the early 1980s, computer graphics was a small, specialized field, largely because the hardware was expensive and graphics-based application programs that were easy to use and cost-effective were few. Then, personal computers with built-in raster graphics display such as the Xerox Star and, later, the mass-produced, even less expensive Apple Macintosh and the IBM PC and its clones popularized the use of bitmap graphics for user-computer interaction. A bitmap is a ones and zeros representation of the rectangular array of points on the screen.
The concept of a “desktop” now became a popular metaphor for organizing screen space. By means of a window manager, the user could create, position, and resize rectangular screen areas, called windows, that acted as virtual graphics terminals, each running an application. Almost all interactive application programs, even those for manipulating text or numerical data, use graphics extensively in the user interfaces and for visualizing and manipulating the application-specific objects. Graphics interaction via raster displays has replaced most textual interaction with alphanumeric terminals.
Even people who do not use computers in their daily work encounter computer graphics in television commercials and as cinematic special effects.
Computer graphics is an integral part of all computer user interfaces, and is indispensable for visualizing two-dimensional (2D), three-dimensional (3D), and higher-dimensional objects. Areas as diverse as education, science, engineering, medicine, commerce, the military, advertising, and entertainment all rely on computer graphics.
Applications of Computer graphics:
The development of computer graphics has been driven both by the needs of the user community and by advances in hardware and software. The application of computer graphics are many and varied; we can, however, divide them into four major areas:
• Display of information
• Design
• Simulation and animation
• User interfaces
Display of Information:
Classical graphics techniques arose as a medium to convey information among people. The human visual system is unrivaled both as a processor of data and as a pattern recognizer. For centuries, cartographers have developed maps to display celestial and geographical information.
We have computer plotting packages that provide a variety of plotting techniques and color tools that can handle multiple large data sets. The field of information visualization is becoming increasingly more important as we have to deal with understanding complex phenomena from problems in bioinformatics to detecting security threats.
Modern imaging technologies such as computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and positron-emission tomography (PET)-generate three dimensional data that must be subjected to algorithmic manipulation to provide useful information.
The field of scientific visualization provides graphical tools that help these researchers interpret the vast quantity of data that they generate. The system used a mathematical model
to generate the data. The field of information uses computer graphics to aid in the discovery of relationships in data sets in which there is no physical tie between u\the data and how they are visualized.
design:
Professional such as engineering and architecture are concerned with design. Design is an iterative process. Rarely in the real world is a problem specified such that there is a unique optimal solution. Design problems are either over determined, such that they posses no solution that satisfies all the criteria, much less an optimal solution, or undetermined, such that they have multiple solutions that satisfy the design criteria. Thus, the designer works iteratively.
The use of interactive graphical tools in computer-aided design (CAD) pervades fields including as architecture, mechanical engineering, the design of very-large-scale integrated (VLSI) circuits, and the creation of characters for animations. After the user produces a possible design, other tools analyze the design and display the analysis graphically.
Simulation And Animation:
Once graphics systems evolved to be capable of generating sophisticated images in real time, engineers and researchers began to use them as simulators. One of the most important uses has been in the training of pilots. Graphical flight simulators have proved to increase safety and to reduce training expenses. The use of special VLSI chips has led to a generation of arcade games s as sophisticated as flight simulators.
The success of flight simulators led to the use of computer graphics for animation in the television, motion picture, and advertising industries. The graphics to drive interactive video games make heavy use of both standard commodity computers and specialized hardware boxes.
The graphics technology for games, both in the firm of the graphics processing units that are on graphics cards in personal computers and in game boxes such as the Xbox and the PlayStation, is being used for simulation rather than expensive specialized hardware.
User Interfaces:
Interaction with computers has become dominated by a visual paradigm that includes windows, icons, menus, and plotting device, such as mouse. More recently, millions of people have become Internet users. Their access through graphical network browsers, such as Firefox and Internet Explorer, that uses these same interface tools
User interfaces demonstrate the variety of the tools available in high level modeling packages and the interactive devices the user can employ in modeling geometric objects.