Lec 01 02 Introduction to Computer Graphics PDF

Computer Graphics Lec 01 Introduction to Computer Graphics Dr Adel Khaled  Instructor’s information A. Prof. Adel Khaled Email: [email protected] Office hours: Monday (all day) Office: Tel/WhatsApp: 00201009878330 ...

Computer Graphics Lec 01 Introduction to Computer Graphics Dr Adel Khaled  Instructor’s information A. Prof. Adel Khaled Email: [email protected] Office hours: Monday (all day) Office: Tel/WhatsApp: 00201009878330  Course information Contact hours: 4.5h Lectures_1: Monday 08:30 am to 10:00 am (1.5 h). Lectures_2: Monday 10:30 am to 11:40 am (1.5 h). Section: Monday 01:10 pm to 14:40 pm (1.5 h). Lab: Monday 14:50 pm to 16:20 pm (1.5 h). Classroom location: 132A classroom and Lab 202 Workload distribution: 40% final exam (40 Marks) 20% midterm exam (20 Marks) 20% Lab exam (10 Marks) 10% Attendance(10 Marks) 10% Quizzes (10 Marks) Class instructions References Computer Graphics with OpenGL, 4th Edition, Donald Hearn and M. Pauline Baker, Prentice Hall, 2016. Computer Graphics Principles & practice”, second edition in C, Foley, VanDam, Feiner and Hughes, Pearson Education.  Course objectives 1. Understand fundamental concepts and algorithms: Students will learn the core concepts, mathematical foundations, and key algorithms used in computer graphics, including 2D and 3D transformations, rendering techniques, modeling approaches, and graphics pipeline operations. 2. Develop practical programming skills: Students will gain hands-on experience in designing and implementing interactive graphics applications using industry-standard APIs and tools like OpenGL or WebGL. This includes creating 2D and 3D graphics, animations, and basic user interfaces. 3. Apply graphics techniques to solve visual computing problems: Students will learn to analyze visual computing challenges and apply appropriate graphics algorithms and techniques to create effective solutions. This includes understanding tradeoffs between different approaches and selecting suitable methods for specific graphics applications. Outlines Introduction History of computer graphics Advantages of computer graphics Application of computer graphics Graphics Systems  Introduction Computer graphics is an art of drawing pictures, lines, charts, etc. using computers with the help of programming. Computer graphics image is made up of number of pixels. Pixel is the smallest addressable graphical unit represented on the computer screen.  Introduction Computer Graphics is defined as methods and techniques for converting data to and from graphical display via computer system. Computer Graphics involves display, manipulation and storage of pictures and experimental data for proper visualization using a computer. Computer Graphics studies the means to model, represent, manipulate, and display geometric objects with computers  Introduction Computer is information processing machine. User needs to communicate with computer and the computer graphics is one of the most effective and commonly used ways of communication with the user. It displays the information in the form of graphical objects such as pictures, charts, diagram and graphs.  Introduction In computer graphics picture or graphics objects are presented as a collection of discrete pixels. We can control intensity and color of pixel which decide how picture look like. The special procedure determines which pixel will provide the best approximation to the desired picture or graphics object this process is known as Rasterization. The process of representing continuous picture or graphics object as a collection of discrete pixels is called Scan Conversion.  History of computer graphics ✓ During the late 1970s, personal computers became more powerful, capable of drawing both basic and complex shapes and designs. ✓ In the 1980s, artists and graphic designers began to see the personal computer, particularly the Commodore Amiga and Macintosh, as a serious design tool, one that could save time and draw more accurately than other methods. ✓ 3D computer graphics became possible in the late 1980s with the powerful (Silicon Graphics International) SGI computers, which were later used to create some of the first fully computer-generated short films at Pixar. ✓ The Macintosh remains one of the most popular tools for computer graphics in graphic design studios and businesses.  History of computer graphics ✓ Modern computer systems, dating from the 1980s and onwards, often use a graphical user interface (GUI) to present data and information with symbols, icons and pictures, rather than text. ✓ Graphics are one of the five key elements of multimedia technology3D graphics became more popular in the 1990s in gaming, multimedia and animation. ✓ In 1995, Toy Story, the first full-length computer-generated animation film, was released in cinemas worldwide. ✓ In 1996, Quake, one of the first fully 3D games, was released. Quake is a series of first- person shooter video games. ✓ Since then, computer graphics have become more accurate and detailed, due to more advanced computers and better 3D modeling software applications, such as Cinema 4D. History of computer graphics  Advantages of computer graphics Computer graphics is one of the most effective and commonly used ways of communication with computer. It provides tools for producing picture of “real-world” as well as synthetic objects such as mathematical surfaces in 4D and of data that have no inherent geometry such as survey result. It has ability to show moving pictures thus possible to produce animations with computer graphics. With the use of computer graphics, we can control the animation by adjusting the speed, portion of picture in view the amount of detail shown and so on.  Advantages of computer graphics It provides tools called motion dynamics. In which user can move objects as well as observes as per requirement for example walk throw made by builder to show flat interior and surrounding. It provides facility called update dynamics. With this we can change the shape color and other properties of object. Now in recent development of digital signal processing and audio synthesis chip the interactive graphics can now provide audio feedback along with the graphical feed backs.  Application of computer graphics Computer graphics deals with creation, manipulation and storage of different type of images and objects. Some of the applications of computer graphics are: Application of computer graphics Application of computer graphics  Application of computer graphics Computer Aided Design  Application of computer graphics Education and Scientific Visualization  Application of computer graphics Graphical User Interface  Application of computer graphics User interface: - Visual object which we observe on screen which communicates with user is one of the most useful applications of the computer graphics. Plotting of graphics and chart in industry, business, government and educational organizations drawing like bars, pie-charts, histogram’s are very useful for quick and good decision making. Office automation and desktop publishing: - It is used for creation and dissemination of information. It is used in in-house creation and printing of documents which contains text, tables, graphs and other forms of drawn or scanned images or picture.  Application of computer graphics Computer aided drafting and design: - It uses graphics to design components and system such as automobile bodies structures of building etc. Simulation and animation: - Use of graphics in simulation makes mathematic models and mechanical systems more realistic and easy to study. Art and commerce: - There are many tools provided by graphics which allows used to make their picture animated and attracted which are used in advertising. Process control: - Now a day’s automation is used which is graphically displayed on the screen.  Application of computer graphics Cartography: - Computer graphics is also used to represent geographic maps, weather maps, oceanographic charts etc. Education and training: - Computer graphics can be used to generate models of physical, financial and economic systems. These models can be used as educational aids. Image processing: - Various kinds of photographs or images require editing in order to be used in different places. Processing of existing images into refined ones for better interpretation is one of the many applications of computer graphics.  Graphics Systems A block diagram of our system is shown in fig1.2. There are four key types of elements in our system: 1. A processor 2. Memory 3. Output devices 4. Input devices Typical graphics system comprises of a host computer with support of fast processor, large memory, frame buffer and Display devices (color monitors), Input devices (mouse, keyboard, joystick, touch screen, trackball), Output devices (LCD panels, laser printers, color printers. Plotters etc.). Interfacing devices such as, video I/O, TV interfaces etc.  Graphics Systems 1. Display processors Display processors are also designed to perform a number of additional operations. These functions include generating various line styles (dashed, dotted, or solid), displaying color areas, and applying transformations to the objects in a scene. Also, display processors are typically designed to interface with interactive input devices, such as a mouse.  Graphics Systems To reduce memory requirements in raster systems, methods have been devised for organizing the frame buffer as a linked list and encoding the color information. One organization scheme is to store each scan line as a set of number pairs. The first number in each pair can be a reference to a color value, and the second number can specify the number of adjacent pixels on the scan line that are to be displayed in that color. This technique, called run-length encoding, can result in a considerable saving in storage space if a picture is to be constructed mostly with long runs of a single color each.  Graphics Systems 2. Input Devices: They are used to get data into the system. Most graphics systems provide a keyboard and at least one other input device. Each of them provide positional information to the system, and each usually is equipped with one or more buttons to provide signals to the processor. The graphics input devices(Analog devices & Digital devices) are devices that allow the information from outside the computer to be communicated with the computer  Graphics Systems 2. Input Devices: Analog Input Devices examples: ◼ Track ball ◼ Joystick ◼ Mouse ◼ Image Scanner The analog input devices need analog to digital converter (A/D) to change the analog signals to a digital form understandable by the processors.  Graphics Systems 2. Input Devices: ❑ Mouse The mouse is an integral part of the graphical user interface (GUI) of any personal computer. The mouse is one of the input analog graphic devices that use the setting of variable resistors to compute the location of the ball of the mouse. As the ball is moved over the surface in any direction, a sensor sends impulses to the computer that causes a mouse-responsive program to reposition a visible indicator (called a cursor) on the display screen. The positioning is relative to some variable starting place. Viewing the cursor's present position, the user readjusts the position by moving the mouse.  Graphics Systems 2. Input Devices: ❑ Track balls and joysticks Usually used in computer games. The joystick and trackball work with variable resistors as the mouse. These are analog input devices which are controlled by transducers. Transducer is a device which converts the user's movements into changes in voltage or amperage by varying the resistance of the circuit. The user rolls the ball located on top of the track ball, with the finger to control the cursor movement. The advantage of trackballs over mouse is that the trackball is stationary, so it does not require much space to use it.  Graphics Systems 2. Input Devices: ❑ Track balls and joysticks Large trackballs are sometimes seen on computerized special-purpose workstations, such as the radar consoles in an air-traffic control room or sonar equipment on a ship or submarine. However, military mobile anti-aircraft radars, commercial airliners (such as Airbus A380 and Airbus A350) and submarine sonars tend to continue using trackballs, since they can be made more durable and more fit for fast emergency use. Large and well made ones allow easier high precision work, for which reason they may still be used in these applications (where they are often called "tracker balls") and in computer-aided design.  Graphics Systems 2. Input Devices: ❑ Track balls and joysticks A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. A joystick, also known as the control column, is the principal control device in the cockpit of many civilian and military aircraft, either as a center stick or side-stick. It often has supplementary switches to control various aspects of the aircraft's flight. Joystick is considered as a lever that moves in all directions and controls the movement of a pointer or some other display symbol. With a joystick, the pointer continues moving in the direction the joystick is pointing. To stop the pointer, you must return the joystick to its upright position. Spring loaded joysticks return to the upright position when released.  Graphics Systems 2. Input Devices: ❑ Keyboard Keyboards are devices contain their own chips. Keyboards are Good for entering alpha numeric data. The computer encodes the keyboard characters using the American Standard Code for Information Interchange (ASCII). Each key has a unique 7-bit ASCII code associated with it, with which we can communicate with the computer. Each key acts as a switch which closes when the key is pressed. If the key is pressed, a code is sent to the processing unit. The CPU then translates that code into an ASCII code which is used in the computer program.  Graphics Systems 2. Input Devices: ❑ Light pen A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's cathode-ray tube (CRT) display. light pen allows the user to point to displayed objects or draw on the screen in a similar way to a touch screen but with greater positional accuracy. A light pen detects changes of brightness of nearby screen pixels when scanned by CRT electron beam and communicates the timing of this event to the computer. Since a CRT scans the entire screen one pixel at a time, the computer can keep track of the expected time of scanning various locations on screen by the beam and infer the pen's position from the latest timestamp.  Graphics Systems 2. Input Devices: ❑ Light pen The light pen contains a photocell that detects the electron beam as it scans across the CRT screen. When the pen is pointed at the screen and a button is pressed, the photocell detects the beam and sends a signal to the computer. The computer can determine the X-Y coordinates of the pen based on the timing of the signal relative to the CRT scanning  Graphics Systems 2. Input Devices: ❑ Image Scanner An image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting or an object and converts it to a digital image. Commonly used in offices are variations of the desktop flatbed scanner where the document is placed on a glass window for scanning. Hand-held scanners, where the device is moved by hand, have evolved from text scanning "wands" to 3D scanners used for industrial design, reverse engineering, test and measurement, orthotics, gaming and other applications. 2. Input Devices: Graphics Systems ❑ Image Scanner A scanner shines light at an image, document, or object. Reflected light is directed onto photosensitive technology via mirrors and lenses. The light is converted into electronic data to form a digital copy of the original. Most scanners use the single pass method, splitting the image into three smaller versions and combining the data from the CCD array into a full-color image. The scanning unit moves across the image, shining light on it, which is then reflected and captured by CCD sensors A charge-coupled device (CCD) is an integrated circuit containing an array of linked capacitors. Each capacitor can transfer its electric charge to a neighboring capacitor under the control of an external circuit. CCD sensors are a major technology used in digital imaging.  Graphics Systems 2. Input Devices: ❑ Touch screens  Graphics Systems 3. Output devices Display devices are also known as output devices. Most commonly used output device in a graphics system is a video monitor. An output device is any piece of computer hardware equipment which converts information into a human-readable form. It can be text, graphics, tactile, audio, and video. Some of the output devices are Visual Display Units (VDU) i.e. a Monitor, Printer graphic Output devices, Plotters, Speakers etc. A new type of Output device is being developed these days, known as Speech synthesizer, a mechanism attached to the computer which produces verbal output sounding almost like human speeches.  Graphics Systems 3. Output devices The following display devices are used: Refresh Cathode Ray Tube. Random Scan and Raster Scan. Color CRT Monitors. Direct View Storage Tubes. Flat Panel Display. Lookup Table.  Graphics Systems 3. Output devices The graphical output devices can be categorized as: 1. Softcopy devices: are these devices produce volatile copy of the image. Example of some Softcopy devices: Monitors (Screens). 2. Hardcopy devices: are these devices that produce permanent pictures that can be documented. Example of some Hardcopy devices: plotters, printers, ink-jitters,… ect.  Graphics Systems 3. Output devices ❑ Cathode-ray-tubes The first cathode ray tube scanning device was invented by the German scientist Karl Ferdinand Braun in 1897. A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, the beams of which are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictures (television set, computer monitor), radar targets, or other phenomena. A CRT on a television set is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer.  Graphics Systems 3. Output devices ❑ Cathode-ray-tubes An electron gun at the rear of the tube produce a beam of electrons which is directed towards the screen of the tube by a high voltage typically 15000 to 20000 volts. Inner side screen is coated with phosphor substance which gives light when it is stroked bye electrons. Control grid controls velocity of electrons before they hit the phosphor. The control grid voltage determines how many electrons are actually in the electron beam. The negative the control voltage is the fewer the electrons that pass through the grid. Thus control grid controls Intensity of the spot where beam strikes the screen. The focusing system concentrates the electron beam so it converges to small point when hits the phosphor coating.  Graphics Systems 3. Output devices ❑ Cathode-ray-tubes Deflection system directs beam which decides the point where beam strikes the screen. Deflection system of the CRT consists of two pairs of parallel plates which are vertical and horizontal deflection plates. Voltage applied to vertical and horizontal deflection plates is control vertical and horizontal deflection respectively.  Graphics Systems Techniques for producing images on the CRT screen: 1: Vector scan/Random scans display. 2: Raster scans display.  Graphics Systems 1. Vector scan/Random scan display Vector scan display directly traces out only the desired lines on CRT. If we want line between point p1 & p2 then we directly drive the beam deflection circuitry which focus beam directly from point p1 top2. If we do not want to display line from p1 to p2 and just move then we can blank the beam as we move it. To move the beam across the CRT, the information about both magnitude and direction is required. This information is generated with the help of vector graphics generator  Graphics Systems 1. Vector scan/Random scan display Display controller is connected as an I/O peripheral to the CPU. Display buffer stores computer produced display list or display program. The Program contains point & line plotting commands with end point co-ordinates as well as character plotting commands. Display controller interprets command and sends digital and point co- ordinates to a vector generator. Vector generator then converts the digital co-ordinate value to analog voltages for beam deflection circuits that displace an electron beam which points on the CRT’s screen. In this technique beam is deflected from end point to end point hence this techniques is also called random scan.  Graphics Systems 1. Vector scan/Random scan display We know as beam strikes phosphors coated screen it emits light but that light decays after few milliseconds and therefore it is necessary to repeat through the display list to refresh the screen at least 30 times per second to avoid flicker. As display buffer is used to store display list and used to refreshing, it is also called refresh buffer  Graphics Systems 1. Vector scan/Random scan display The advantages include 1. Very high resolution, limited only by monitor 2. Easy animation, just draw at different positions 3. Requires little memory (just enough to hold the display program) 4. Have arbitrary resolution 5. Good for line draws The disadvantages are 1. Requires "intelligent electron beam, i.e., processor controlled 2. Limited screen density, can’t draw a complex image 3. Limited color capability (very expensive) 4. They may draw the same point twice 5. It is hard to do color changes.  Graphics Systems 2: Raster scan display Raster Scan Displays are most common type of graphics monitor which employs CRT. It is based on television technology. In raster scan system electron beam sweeps across the screen, from top to bottom covering one row at a time.... This memory area holds intensity values for all screen points.  Graphics Systems 2: Raster scan display The video controller reads this refresh buffer and produces the actual image onscreen. It will scan one line at a time from top to bottom & then back to the top. Video controller or display controller is used to control the operation of the display device. The advantages include 1. It is bounded size 2. Good for color images and general purpose. The disadvantages include 1. It has bounded resolution 2. Every pixel has to be stored.  Graphics Systems The most important task for the video controller is the constant refresh of the display. There are two fundamental types of refresh: 1. Interlaced ‫متشابك‬ 2. Non-interlaced Graphics Systems Interlaced The former is used in broadcast television and in raster displays designed to drive regular televisions. In interlaced displays, odd rows and even rows are refreshed alternately. An interlaced display operating at 60 Hz, the screen is redrawn in entirety only 30 times per second, although the visual system is tricked into thinking the refresh rate is 60 Hz rather than 30 Hz. Graphics Systems Non-interlaced Non-interlaced displays, the pixels are displayed row by row, or scan line by scan line, at the refresh rate, which is usually 50 to 85 times per second, or 50 to 85 hertz( Hz).  Graphics Systems The output from the video controller has one of the three forms: RGB, monochrome, or NTSC. A. RGB (red, green, blue), separate cables carry the red, green, and blue signals to control the three electron guns of a shadow- mask CRT, and another cable carries the synchronization to signal the start of vertical and horizontal retrace. There are standards for voltages, wave shapes, and synchronization timings of the RGB signals. B. Monochrome signal use the same standards but have only intensity and synchronization cables, or merely a single cable carrying composite intensity and synchronization. C. NTSC (National Television System Committee) video is the signal format used in North American commercial television. Color, intensity, and synchronization information is combined into a signal with a bandwidth of about 5 MHz, broadcast as 525 scan lines, in two fields of 262.5 lines each. Just 480 lines are visible, the rest occur during the vertical retrace periods at the end of each field. Graphics Systems 1. Color CRT monitors A CRT monitors displays color pictures by using a combination of phosphors that emit different colored light. It produces range of colors by combining the light emitted by different phosphors. There are three basic techniques: A. Beam-penetration technique B. Shadow-Mask C. Direct-view storage tubes  Graphics Systems 1: Beam-penetration technique The Beam-Penetration method has been used with random-scan monitors. In this method, the CRT screen is coated with two layers of phosphor, red and green and the displayed color depends on how far the electron beam penetrates the phosphor layers. This method produces four colors only, red, green, orange and yellow. A beam of slow electrons excites the inner red layer only; hence screen shows red color only. A beam of high-speed electrons excites the outer green layer. Thus screen shows a green color.  Graphics Systems 1: Beam-penetration technique At intermediate beam speed we can produce combination of red and green lights which emit additional two colors orange and yellow. The beam acceleration voltage controls the speed of the electrons and hence color of pixel. It is a low cost technique to produce color in random scan monitors. It can display only four colors. Quality of picture is not good compared to other techniques.  Graphics Systems 2: Shadow-Mask CRT has 3 phosphor color dots at each pixel position, and it has 3 guns R, G, B. The shadow mask contains a set of holes aligned with the phosphor pattern, when the beams pass through a hole in the shadow mask, it activates a dot triangle The shadow mask is one of the two technologies used in the manufacture of cathode ray tube (CRT) televisions and computer displays which produce clear, focused color images. A shadow mask is a metal plate punched with tiny holes that separate the colored phosphors in the layer behind the front glass of the screen.  Graphics Systems Shadow mask produces wide range of colors as compared to beam- penetration technique. This technique is generally used in raster scan displays. Including color TV. In this technique CRT has three phosphor color dots at each pixel position. One dot for red, one for green and one for blue light. This is commonly known as Dot Triangle. A dot triangle when activated appears as a small dot on the screen which has color of combination of three small dots in the dot triangle. By changing the intensity of the three electron beams we can obtain different colors in the shadow mask CRT.  Graphics Systems 3: Direct-view storage tubes (DVST) DVST terminals also use the random scan approach to generate the image on the CRT screen. The term "storage tube" refers to the ability of the screen to retain the image which has been projected against it, thus avoiding the need to rewrite the image constantly. Function of guns: Two guns are used in DVST 1. Primary guns: It is used to store the picture pattern. 2. Flood gun or Secondary gun: It is used to maintain picture display.  Graphics Systems Advantage of DVST 1. Refreshing of CRT is not required. 2. Very complex pictures can be displayed at very high resolution without flicker. 3. Flat screen. Disadvantage of DVST 1. They do not display color and are available with single level of line intensity. 2. For erasing it is necessary to removal of charge on the storage grid so erasing and redrawing process take several second. 3. Erasing selective part of the screen cannot be possible. 4. Cannot used for dynamic graphics application as on erasing it produce unpleasant flash over entire screen. 5. It has poor contrast as a result of the comparatively low accelerating potential applied to the flood electrons. 6. The performance of DVST is somewhat inferior to the refresh CRT.  Graphics Systems 1: Frame buffer The frame buffer is a video output device that drives a video display from a memory buffer containing a complete frame of data. The information in the buffer typically consists of color values for every pixel (point that can be displayed) on the screen.  Graphics Systems 1: Frame buffer Color values are commonly stored in 1-bit monochrome, 4-bit palletized, 8-bit palletized, 16-bit high color and 24-bit true color formats. An additional alpha channel is sometimes used to retain information about pixel transparency. The total amount of the memory required to drive the frame buffer is dependent on the resolution of the output signal, as well as the color depth and palette size. The frame buffer refers to the memory dedicated to storing the image. Graphics Systems 1: Frame buffer It would generally be a 2D array of pixels, where each pixel stores a color. Color is typically stored as a 24 bit RGB value. This offers 8 bits (256 levels) for red, green, and blue, for a total of 16,777,216 different colors. Very often, additional data is stored per pixel such as depth (z). Size of frame buffer = height * width * no of bits per pixel = H*W*b  Graphics Systems 1: Frame buffer Frame buffer Disadvantages It occupies a large memory space It doesn’t provide a large number of colors (image resolution decreases) The solution will be via LUT (look-up table) A color display system that incorporates an LUT  Graphics Systems 2: Look-Up Table (LUT) Simply, a LUT is a table of equivalents that convert brightness and darkness in an image into numbers. Thus in an 8-bit gray scale system, black is set to zero, and white is 255, and all of the other gradations of intensity are given values between them.  Graphics Systems 2: Look-Up Table (LUT) LUT is the table that offers a programmable association between a pixel values and the final displayed color. if a raster display has a color depth of b bits (so that there are b bit planes in its frame buffer) and each LUT entry is n bit wide. Using Frame Buffer alone, the system can display 2b colors maximum. While adding the LUT, the system can display 2n colors maximum (i.e. more existing colors → higher resolution) ▪ No. of memory bytes required by the LUT = (n*2b)/8 n: number of registers in memory  Graphics Systems 3: True-Color Frame Buffers 1. Each pixel requires at least 3 bytes. One byte for each primary color. 2. Sometimes combined with a look-up table per primary. 3. Each pixel can be one of 2^24 colors. 4. Worry about your Endians. 5. Each pixel requires at least 3 bytes. One byte for each primary color. 6. Sometimes combined with a look-up table per primary. 7. Each pixel can be one of 2^ 3x8 = 2 ^24 colors The endianness of the system affects how multi-byte color values are stored in memory for the LUT. For example, in a 3D RGB LUT: On a little-endian system, the bytes for each color channel may be stored as: B, G, R On a big-endian system, they may be stored as: R, G, B 1. Difference between random scan and raster scan Base of Raster Scan System Random Scan System Difference The electron beam is swept across the The electron beam is directed only to Electron Beam screen, one row at a time, from top to the parts of screen where a picture bottom. is to be drawn. Its resolution is poor because raster Its resolution is good because this system in contrast produces zigzag lines system produces smooth lines Resolution that are plotted as discrete point sets. drawings because CRT beam directly follows the line path. Picture definition is stored as a set of Picture definition is stored as a set of Picture Definition intensity values for all screen points, line drawing instructions in a display called pixels in a refresh buffer area. file. The capability of this system to store These systems are designed for line- intensity values for pixel makes it well drawing and can’t display realistic Realistic Display suited for the realistic display of scenes shaded scenes. contain shadow and color pattern. Screen points/pixels are used to draw Mathematical functions are used to Draw an Image an image. draw an image.  Graphics Systems 1. Modern Display Technologies ❑ Video Display (B/W & Colored) (Raster Scan / Random Scan CRT display) ❑ Liquid Crystal Display (LCD’s) ❑ Plasma Display ❑ Field Emission Display (FED’s) ❑ Light Emitting Diode (LED’s) ❑ Digital Micro mirror Devices (DMD) ❑ Liquid Crystal on Silicon (LCOS Technology) ❑ Gratings Light Valves (GLV Technology