1. Introduction to Computer Graphics PPT1: Principles of Graphics Systems
EEL
Introduction to Computer Graphics
PPT1: Principles of Graphics Systems
Akshay Rao Voora U

2. Display Devices
Cathode-ray tube (CRT) architecture

3. Display Devices Invented by Karl Ferdinand Braun (1897).
Beam of electrons directed from cathode (-)to phosphor-coated (fluorescent) screen (anode (+)).
Directed by magnetic focusing and deflection coils (anodes) in vacuum filled tube.
Phosphor emits photon of light, when hit by an electron, of varied persistence (long ms for texts / short < 1ms for animation) .
Refresh rate (50-60 Hz / Hz) to avoid flicker / trail.
Phosphors are organic compounds characterized by their persistence and their color (blue, red, green).

4. Horizontal deflection and vertical deflection direct the electron beam to any point on the screen.
Intensity knob, regulates the flow of electrons by controlling the voltage at the control grid.
Accelerating voltage from positive coating inside screen (anode screen) or an accelerating anode.
Focusing forces the electron beam to converge to a point on the monitor screen and can be electrostatic (lens) or magnetic (field)
Persistence is defined as the time taken by the emitted light from the screen to decay to one-tenth of its original intensity.
Flicker: At low refresh rates (60 Hz and below), the periodic scanning of the display may produce a flicker that some people perceive more easily than others, especially when viewed with peripheral vision.

5. Fluorescence: It is the light emitted as electrons their excess energy while the phosphor is being struck by electrons.
Phosphorescence: It is the light given off by the return of the relatively more stable excited electrons to their unexcited state, once the electron beam excitation is removed.
Resolution: It is the maximum number of points that can be displayed without overlap on a CRT.
Spot intensity: It has a Gaussian distribution, so two adjacent spots will appear distinct as long as their separation is greater than the diameter at which each spot has an intensity of about 60 percent of that at the center of the spot.
Horizontal retrace: The return to the left of the screen, after refreshing each scan line, is called the horizontal retrace of the electron beam.
Vertical retrace: At the end of each frame, the electron beam returns to the top left corner of the screen to begin the next frame.

6. Interlacing: Interlacing of the scan lines allows us to see the entire screen displayed in one-half the time it would have taken to sweep across all the lines at once from top to bottom.
Picture storage: Charge distribution is used to store the picture information.
Advantages
No input lag
No ghosting and smearing artifacts during fast motion due to sub-millisecond response time, and impulse-based operation
Near zero color, saturation, contrast or brightness distortion
Can be used or stored in both extreme hot and cold temperature conditions without harm to the system
Excellent viewing angle
High contrast ratio (over 15,000:1), excellent color, fairly wide color gamut and low black level

7. Disadvantages
Large size and weight, especially for bigger screens (a 20-inch (51 cm) unit weighs about 50 lb (23 kg)).
Geometric distortion caused by variable beam travel distances.
A lot of heat can be emitted during operation, due to relatively high power consumption.
Produces noticeable flicker at refresh rates lower than 85 Hz.
Hazardous to repair/service without proper training and precautions taken.
Sensitive to magnetic interference, which can cause the image to shimmer.
A “halo” may appear around bright objects on a mostly dark screen.
Cannot display almost no margin at all on all sides.
The glass envelopes contains toxic lead and barium as X-ray radiation shielding.
The phosphors can also contain toxic elements such as cadmium. Many countries treat CRTs as toxic waste and prohibit their disposal in landfills or by incineration.

8. Display Devices Color Displays
Color CRT’s are designed as RGB monitors also called full-color system or true-color system.
Use shadow-mask methods with intensity from each electron gun (red, green, blue) to produce any color directly on the screen without preprocessing.
Frame buffer contains 24 bits per pixel, for 256 voltage settings to adjust the intensity of each electron beam, thus producing a choice of up to 17 million colors for each pixel.

9. Display Devices Delta – Delta CRTs
A shadow mask CRT has three phosphor color dots at each pixel position.
One phosphor dot emits red light, another emits a green light, and the third emits a blue light.
The three electron beams are deflected and focused as a group onto the shadow mask, which contains a series of holes aligned with the phosphor-dot patterns.
When the three beams pass through a hole in the shadow mask, they activate a dot triangle, which appears as a small color spot on the screen.

10. Display Devices Plasma panel displays
A plasma display is a computer video display in which each pixel on the screen is illuminated by a tiny bit of plasma or charged gas, somewhat like a tiny neon light.
Plasma displays are thinner than cathode ray tube ( CRT ) displays and brighter than liquid crystal displays.
Plasma displays are sometimes marketed as "thin-panel" displays and can be used to display either analog video signals or display modes digital computer input.
In addition to the advantage of slimness, a plasma display is flat rather than slightly curved as a CRT display is and therefore free of distortion on the edges of the screen.
Light Emitting Diodes
This is also a Emissive Technology which contains a matrix of diodes those are arranged on the screen as the pixel position.

11. Display Devices
The picture definition is stored in the Refresh buffer and when information is read from the refresh buffer and then it is converted into the Voltage Levels and it is applied to diodes which produce the light pattern in the display.
Organic LEDs
Organic LEDs function like regular semiconductor LEDs but they emit light.
Thin-film deposition of organic, light-emitting molecules through vapor sublimation in a vacuum.
Dope emissive layers with fluorescent molecules
to create color.
Organic LEDs are transparent, flexible and have
large viewing angle.

12. Display Devices Liquid Crystal Display (LCD)
Used in small systems, such as calculators, laptop computers.
Produce a picture by passing polarized light through a liquid-crystal material that can be aligned to either block or transmit the light.
Two glass plates each containing a light polarizer at right angles to the other plate, sandwich the liquid crystal materials.
Rows of horizontal transparent conductor and columns of vertical conductors.

13. Display Devices Matrix addressing
Matrices are a convenient and efficient way to represent a sequence of transformations
Representing 2D transformation by a matrix
Multiplying matrix by column vector applies transformation to point
Virtual Reality (VR) devices
Head Mounted Displays
The display and a position tracker are
attached to the user’s head

14. Display is stationary, tracker tracks the user’s head relative
Head Tracked Displays
Display is stationary, tracker tracks the user’s head relative
to the display
Stereo Imaging

15. Raster-Scan Systems

16. The image is stored in a frame buffer containing the total screen area and where each memory location corresponds to a pixel.
• In a monochrome system, each bit is 1 or 0 for the corresponding pixel to be on or off (bitmap).
• The display processor scans the frame buffer to turn electron beam on/off depending if the bit is 1 or 0.
• For color monitors, the frame buffer also contains the color of each pixel (color buffer) as well as other characteristics of the image (gray scale, …). 8 bits/pixel  (pixmap).
• Depth of the buffer area is the number of bits per pixel (bit planes), up to 24.
Examples: television panels, printers, PC monitors (99% of raster-scan)...
Refresh rate: 24 is a minimum to avoid flicker, corresponding to 24 Hz (1 Hz = 1 refresh per second)

17. • Current raster-scan displays have a refresh rate of at least 60 frames (60 Hz) per second, up to 120 (120 Hz).
• Uses large memory: 640x480  bits  38 kB
• Refresh procedure:
– Horizontal retrace – beam returns to left of screen
– Vertical retrace – bean returns to top left corner of screen
– Interlaced refresh – display first even-numbered lines, then odd numbered lines permits to see the image in half the time useful for slow refresh rates (30 Hz shows as 60 Hz).

18. Frame Buffer Operations
GPU Power
GPU Power
Architecture of the GPU
GPU
. . .
Input Assembly
Vertex Processing
Frame Buffer Operations L2
Memory Controller
Off-Chip Memory
Geometry Processing

19. Applications of GPU:
GPU Cluster.
Mathematical includes built-in support for CUDA and OpenGL GPU execution.
MATLAB acceleration using the Parallel Computing Toolbox and MATLAB Distributed Computing Server, as well as 3rd party packages like Jacket.
Molecular modeling on GPU.
Deeplearning4j, open-source, distributed deep learning for Java. Machine vision and textual topic modeling tool kit.

20. Graphics Workstations
A workstation is a computer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems.

21. Applications of high output graphics workstations:
Engineering and Design (CAD/CAE/AEC)
Digital Content Creation (DCC) & Digital Media
Geographical Information Systems (GIS) & Visualization
Life Sciences
Oil & Gas

22. Graphical Input Graphics input devices Mouse Key board Track ball
Space ball
Joy stick
Digitizer
Dials
Button Boxes
Principles of 2D and 3D input devices
The 2D input devices are used to convert paper format materials into digital formats
In 3D input devices static replicas of objects can be made and the digital format is translated into the computer

23. Input Devices Graphics input devices Key board Mouse Function Dials
Joy stick
Graphics tablet

24. Input Devices
Data glove

25. Input Devices Scanner types and their main uses Flat bed Scanner
A flatbed scanner is made up of a glass pane and a moving optical CIS or CCD array.
The image the one that is to be scanned is then placed on the glass pane.
The sensor and source of light move across the glass pane to scan the document and produce its digital copy.
Flatbed scanners derive their name from the fact that their glass plane or bed, where the object to be scanned is placed, is flat.

26. 2. Sheet fed Scanner
In this type of scanner, the document is fed into the horizontal or vertical slot provided in it.
The prominent components of a sheet fed scanner include the sheet-feeder, scanning module, and calibration sheet.
While the sensor and source of light move across the glass pane in flatbed scanners, in sheet fed scanners, they are stationary.
Instead, the document moves through the scanner. Ideal for scanning single page documents, these scanners cannot scan thick objects, like books, and that, perhaps, is their major drawback.

27. 3. Hand held Scanner
A handheld scanner is a small manual scanning device which is moved over the object that needs to be scanned
In flat back and sheet fed scanners, you put the document that is to be scanned inside the device
In contrast, in the case of held held scanner, you have to drag it over the document that is to be scanned
Using a handheld scanner can be a cumbersome task as the hand needs to be steady all the time

28. 4. Drum Scanner
A drum scanner is the one which uses a photomultiplier tube (PMT) to scan images instead of the charge-coupled device that is typically used in a flatbed scanner.
Photomultiplier tubes are vacuum tubes which are extremely sensitive to light. In drum scanners, the image is mounted on the glass tube.
When the beam of light moves across the image, its reflection is picked up by the PMT and processed.
Drum scanners are known for their high resolution, which makes them apt for detailed scans

29. Input Devices Optical touch panel
This input method for graphics tablets, which originally did not feature monitors, achieves high-precision touch panels by combining a sensor with the LCD panel.
When the user touches the screen with a special-purpose stylus that generates a magnetic field, sensors on the panel receive the electromagnetic energy and use it to sense the position of the pen.
Electric touch panels
Resistive film represented the most widely used sensing method in the touch panel market.

30. The strengths of this type of touch panel include high light
Touch panels based on this method are called pressure-sensitive or analog-resistive film touch panels.
In addition to standalone LCD monitors, this technology is used in a wide range of small to mid-sized devices, including smart phones, mobile phones, PDAs, car navigation systems, and the Nintendo DS.
Acoustic touch panel
The strengths of this type of touch panel include high light
transmittance and superior visibility, since the structure
requires no film or transparent electrodes on the screen.
Additionally, the surface glass provides better durability
and scratch resistance than a capacitive touch panel.
Another advantage is that even if the surface does
somehow become scratched, the panel remains sensitive
to touch.

31. 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 CRT TV set or monitor
Allows the users to point to displayed objects and
to draw objects on screen
Voice recognizer

32. Hard-Copy Devices
Dot matrix printer: The print head of that printers contains a number of pins and number of pins determines the quality of printers
Laser printer: Laser printers are those printers which first heats a paper , for heating a entire paper a drum is used which rotates the paper and heat that paper and then toner is applied i.e. Ink is sprayed on that paper , then the heated area is printed .
Ink-jet printer: The Ink Jet Printer is that which produces the output by squirting ink or spraying ink in horizontal form . In this first a paper is heated and then Ink will be sprayed on that heated printer
Electrostatic printer: Electrostatic Printers work according to the electric voltage . Before printing this printer first charge that printer by using the negative voltage and When this will pass to the printer , the printer will charge it with the positive so that where it finds the negative voltage this will print a character at that position and this is also based on heat sensitive paper method.

33. Hard-Copy Devices Principles of 3D printing
In 3D printing, additive processes are used, in which successive layers of material are laid down under computer control. These objects can be of almost any shape or geometry, and are produced from a 3D model or other electronic data source. A 3D printer is a type of industrial robot.
Types of 3D printers
Stereo lithography(SLA)
Fused deposition modeling (FDM)
Selective Laser Sintering (SLS)
Selective laser melting (SLM)
Electronic Beam Melting (EBM)
Laminated object manufacturing (LOM)

34. Graphics Software Types of graphics functions Control functions
I/O functions
Modeling functions
Viewing transformations
Attributes selection
Object rendering
Output primitives

35. Sample Program Program to display console
#include “../../shared/gltools.h” // OpenGL toolkit
///////////////////////////////////////////////////////////
// Called to draw scene
voidRenderScene(void) {
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT);
// Flush drawing commands
glFlush(); }
// Set up the rendering state
voidSetupRC(void)
glClearColor(0.0f, 0.0f, 1.0f, 1.0f);

36. ///////////////////////////////////////////////////////////
// Main program entry point
void main(void)
int main(intargc, char* argv[]) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);
glutCreateWindow(“Simple”);
glutDisplayFunc(RenderScene);
SetupRC();
glutMainLoop();
return 0; }

37. Output:

38. References Computer Graphics by Donald Hearn and M. Pauline Baker