![Writing OpenGL Program:
To initialize GLUT:
glutInit(&argc, argv);
To create Display Window:
glutCreateWindow(“My First OpenGL Window”);
What a Display Window is to contain?
glutDisplayFunc(lineSegment);
Display Window is not yet on the screen
All Display Windows we have created are activated by using the following function:
glutMainLoop();
It must be put at the last in the program
argv is a pointer to an array of null terminated strings, and argc
says how large this array is.
These are automatically passed to you when you start your
program and enter main().
argv[0] is a pointer to a string which holds the name of the
executable file, including full path. argv[1] is the first argument
you pass to you program when starting it, and so on.
Like this:
c: est.exe hello world
Then argc=3
argv[0]=“c: est.exe”
argv[1]=“hello”
argv[2]=“world”](https://image.slidesharecdn.com/cglecture1-240217162006-1897696e/85/CG-Lecture-1-pptx-GRAPHIS-VENNELA-DONTHIREDDY-81-320.jpg)
![Positioning a Window
glutInitWindowPosition(50,100);
initial
Specifying the Window Size:
glutInitWindowSize(400, 300);
For Display Window, we can choose a background colour (eg. White) :
glClearColor(1.0, 1.0, 1.0, 0);
R G B Alpha Value
0 = Totally Transparent Object
1 = Opaque Object
To actually put display
window on screen with
the colour values, we
need to invoke one more
function
glClearColor(GL_COLOR_BUFFER_BIT);
glClearColor specifies the red, green, blue, and alpha values used by glClear to clear the color buffers.
Values specified by glClearColor are clamped to the range [0,1]01.](https://image.slidesharecdn.com/cglecture1-240217162006-1897696e/85/CG-Lecture-1-pptx-GRAPHIS-VENNELA-DONTHIREDDY-82-320.jpg)
CG Lecture 1.pptx GRAPHIS VENNELA DONTHIREDDY
- 1. COMPUTER GRAPHICS AND VISUALIZATION CSE304 Subject Teacher: Tejinder Thind L:3, T:1, P:0 Credits: 4
- 2. Text Book Computer Graphics with OpenGL- 4th edition - 2014 Authors: Donald D. Hearn, Pauline Baker, Warren Carithers Publishers: Pearson
- 3. Attendance : 05 marks CA : 25 marks MTT : 20 marks ETT : 50 marks L:3, T:1, P:0 Credits: 4
- 4. CA1 – MCQ based Test on OAS (30 marks) CA2 – Subjective Test (More of Analytical type) (30 marks) -------------------------------------------------------------------------------------------------------------------------- CA 3 (Mandatory) – Mini Project in OpenGL– To be assigned before Mid Term (30 marks) Academic Tasks One best out of two
- 5. Mid Term: MCQ based exam End Term: MCQ + Subjective (Mix)
- 6. Unit I: Introduction to Computer Graphics and OpenGL Unit II: Rasterization and Transformations Unit III: 2D viewing pipeline Unit IV: 3D viewing pipeline Unit V: Visibility and Shading Unit VI: Discrete Techniques and Object Representation What we are going to study in this Subject?
- 13. Course Outcomes CO1 :: Classify and describe various Computer Graphics tools and techniques. CO2 :: Analyze and apply various algorithms of 2D Transformations on different type of objects. CO3 :: Determine and apply appropriate 2D clipping algorithms and various projection techniques on different types of objects. CO4 :: demonstrate and apply various algorithms of 3D Transformations and various projection techniques on different types of objects. CO5 :: observe and differentiate various visibility and shading techniques and models. CO6 :: describe and represent Bezier and B-spline curves with properties.
- 14. Graphics A graphic is an image or pictorial representation of an object. Examples: A line drawn on a paper, an arrow, a geometrical figure, a caricature or a clicked picture Graphics are not new. The earliest graphics known to us are stone age cave paintings (40,000–10,000 B.C.)
- 15. Why Graphics ? Graphics …….is more appealing
- 16. Computer Graphics …offers methods and techniques for generating and manipulating eye catching images with the assistance of a computer …allows the creation, display, and storage of pictures with help of a computer Computer graphics can either be Two-dimensional (2D) Three-dimensional (3D) represent plain objects gives a realistic touch to an object representation
- 17. Computer Graphics Some Examples…… Courtesy: Google -Doodle
- 18. Different content is seen on the display space of Toyota's concept vehicle Fun-Vii. The whole body of the concept car can be used as a display space, with the body colour and display content changeable at will. This allows the vehicle to function as a terminal for displaying messages, advertising or other information. Toyota's concept vehicle Fun-Vii
- 19. Applications of Computer Graphics …and it’s impact on our daily life
- 20. Newspaper Kiosk : Prints paper newspapers on demand for customers from an electronic vending unit in under two minutes. Traditional Newspaper!!!
- 21. THEN…. …. NOW
- 22. Multimedia Audio ( Speeches, Music and other type of sounds ) THEN…. …. NOW
- 23. • Artificial movement of Text and Objects • Can be 2D or 3D
- 24. THEN…. ….NOW
- 25. …in NEWS
- 26. Tring !!! Tring !!! Voice Music Videos Animated Clips Games SMS, Ringtones Internet Word Processors Wallpapers Screen Savers, ….. THEN…. ….NOW Ordinary Phone to Cell-Phone
- 27. ….NOW THEN…. Painter to a Photographer
- 29. Paint Stores Pencil Sketch v/s Multimedia Sketch Video Conferencing Graphical User Interface
- 31. Computer Aided Design (CAD)
- 32. Image Processing
- 34. Virtualization
- 35. To: Touch Technologies 1951 2015 History of Computer Graphics
- 36. 1951: Whirlwind computer 1955: SAGE (Semi-Automatic Ground Equipment) 1959: Design Augmented by Computers-1 (DAC-1), a CAD (computer-aided design) system 1961: first graphical computer game 1963: Sketchpad 1966: VICAR (Video Image Communication and Retrieval 1970: Bézier curves 1970s: 3D computer-graphic animation 1981: Paintbox 1980s: Desktop publishing (designing things on your own small office computer) Aldus PageMaker (1985) and QuarkXPress (1987) 1990: The first version of Adobe PhotoShop 1993: Mosaic, the first web browser to show text and images side-by-side 1995: Toy Story, CGI graphics in moviemaking. 1995: The GIMP (GNU Image Manipulation Program) 1999: SVG (Scalable Vector Graphics) to provide higher-quality images on the Web 2007: iPhone and iPod Touch with touchscreen graphical user interfaces
- 37. Lecture No. 2: Graphics/Video Display Devices …changed our life style
- 38. ….This is what we see ….but we need to know this
- 39. A display device (commonly called a display or screen) is an output device for presentation of information in visual form. Various types of Display Devices: I) Cathode-ray tubes (CRT) Displays • Raster-scan CRTs • Random-scan CRTs • Color CRT displays II) Direct View Storage Tube (DVST)/ Memory Storage Tube Displays III) Flat Panel Monitors • Emissive Devices • Non-Emissive Devices • Thin Film Electroluminescent Displays • Plasma Panel Displays • Liquid Cristal Displays(LCDs)
- 40. Basic Graphics System Input devices Output device Image formed in FB
- 41. Frame Buffer
- 42. Cathode Ray Tube (CRT) Displays …one of the earliest electronic displays is the cathode ray tube (CRT), which was made commercial in 1922. … CRT is a specialized vacuum tube in which images are produced when an electron beam strikes a phosphor- coated screen. …the earliest CRTs were monochrome and were used primarily in oscilloscopes and black and white televisions. …the first commercial colour CRT was produced in 1954. …CRTs were the single most popular display technology used in television sets and computer monitors for over half a century. …it was not until the 2000s that LCDs began to gradually replace them. Oscilloscopes are a common type of test instrument used to capture, analyze and troubleshoot electrical or real world physical signals. In 1897 he built the first cathode-ray tube (CRT) and cathode-ray tube oscilloscope. Karl Ferdinand Braun (a German inventor) Television sets, computers, automated teller machines, video game machines, video cameras, monitors, oscilloscopes and radar displays all contain cathode-ray tubes. In 1907 he used a CRT in the receiver of a television system Boris Rosing (the Russian scientist) Inventors/Contributors:
- 43. (Image from “Computer Graphics C Version” by Donald Hearn and Pauline Baker)
- 44. - Beam of electrons (-)directed from cathode to phosphor-coated (fluorescent) screen (anode (+)) - Electron beam is directed by magnetic focusing anode and deflection coils in vacuum tube – Intensity knob: regulates the flow of electrons by controlling the voltage at the control grid |-- high voltage reduces the electron density and thus brightness |-- low voltage increases the electron density and thus brightness – Focusing anode/system forces the electron beam to converge to a point on the monitor screen |-- Can be electrostatic (lens) or magnetic (field) - Deflection directs the electron beam horizontally or vertically to any point on the screen |-- Can be controlled by electric (deflection plates) or magnetic fields (deflection coils) |-- Magnetic coils: two pairs (top/bottom, left/right) of tube neck |-- Electric plates: two pairs (horizontal, vertical) - Phosphor(an organic compound) emits photon of light, when hit by an electron, of varied persistence (long 15-20 ms for texts / short < 1ms for animation) Image maintenance – Positive charge distribution to store picture information – Refresh CRT: refreshes the display constantly to maintain phosphor glow. Refresh rate (50-60 Hz / 72-76 Hz) to avoid flicker / trail (Image from “Computer Graphics C Version” by Donald Hearn and Pauline Baker)
- 45. Characteristics of Cathode-Ray Tube (CRT) – Intensity is proportional to the number of electrons repelled in beam per second (brightness) – Resolutionis the maximum number of points that can be displayed without overlap; ….is expressed as number of horizontal points by number of vertical points; ….points are called pixels (picture elements); example: resolution 1024 x 768 pixels. ….typical resolution is 1280 x 1024 pixels. Pros • High contrast • Excellent color • No native resolution; Able to display many different resolutions and refresh rates • No input lag • No ghosting and smearing artifacts during fast motion • Nearly zero color, saturation, contrast or brightness distortion. • Excellent viewing angle. • Allows the use of light guns/pens. • Can be used or stored in both extreme hot and cold temperature conditions without harm to the system Cons • Large size and weight • High power consumption( 2-10 times in comparison to LCD monitor) • Produces noticeable flicker at refresh rates lower than 85 Hz. • The glass envelopes contains toxic lead and barium as X-ray radiation shielding. The phosphors can also contain toxic elements such as cadmium. • Sensitive to magnetic interference, which can cause the image to shimmer or the colors to shift.
- 46. Raster Scan CRT
- 47. Random Scan CRT
- 48. Coloured CRTs: BEAM PENETRATION METHOD
- 49. Coloured CRTs: SHADOW MASK METHOD
- 50. Working of SHADOW MASK CRT
- 51. Next Generation Display Technologies Display technology: IPS (In-plane switching)LCDs Organic light-emitting diode (OLED) Organic light-emitting transistor (OLET) Surface-conduction electron-emitter display (SED) Quantum Dots Displays Curved and Flexible Displays Full and Wide Color Gamut Displays 4K UHD and High Resolution High PPI Displays Very Bright Low Reflectance High Ambient Light Displays Low Temperature Polysilicon (LTPS) Displays IGZO(Indium Gallium Zinc Oxide) Displays Links for Detailed Study: https://en.wikipedia.org/wiki/Next_generation_of_display_technology http://www.displaymate.com/Display_Technology_2014.htm
- 52. Old age CRTs ………. to ……………
- 53. Flat Panel Monitors The term Flat-panel display refers to a class of video devices that have reduced volume, weight and power requirements compared to a CRT. They are thinner than CRTs. Flat Panel Monitors Emissive displays Non-emissive displays (or emitters) …converts electrical energy into light • Plasma panels • Thin-Film Electroluminescent Displays • Light-emitting diodes …use optical effects to convert sunlight or light from some other source into graphics patterns. (or nonemitters) • Liquid-Crystal Displays (LCDs)
- 54. PLASMA PANEL DISPLAYS …also called gas-discharge displays. • Constructed by filling the region between two glass plates with a mixture of gases that usually includes neon. • A series of vertical conducting ribbons is placed on one glass panel, and a set of horizontal ribbons is built into the other glass panel. • Firing voltages applied to a pair of horizontal and vertical conductors cause the gas at the intersection of the two conductors to break down into a glowing plasma of electrons and ions. • Picture definition is stored in a refresh buffer, and the firing voltages are applied to refresh the pixel positions 60 times per second. Tip: a conductor is an object or type of material that allows the flow of electrical current in one or more directions.
- 55. THIN-FILM ELECTROLUMINESCENT DISPLAYS • Thin-film electroluminescent displays are similar in construction to a plasma panel. • The difference is that the region between the glass plates is filled with a phosphor, such as zinc sulphide doped with manganese, instead of a gas. • When a sufficiently high voltage is applied to a pair of crossing electrodes, the phosphor becomes a conductor in the area of the intersection of the two electrodes. • Electrical energy is then absorbed by the manganese atoms, which then release the energy as a spot of light similar to the glowing plasma effecting a plasma panel. • Electroluminescent displays require more power than plasma panels, and good colour and grayscale displays are hard to achieve.
- 56. • A third type of emissive device is the light-emitting diode (LED). • A matrix of diodes is arranged to form the pixel positions in the display, and picture definition is stored in a refresh buffer. • As in scan-line refreshing of a CRT, information is read from the refresh buffer and converted to voltage levels that are applied to the diodes to produce the light patterns in the display. LIGHT-EMITTING DIODES (LED)
- 57. • These non-emissive devices produce a picture by passing polarized light from the surroundings or from an internal light source through a liquid-crystal material that can be aligned to either block or transmit the light. • Flat-panel displays commonly use nematic (threadlike) liquid-crystal compounds that tend to keep the long axes of the rod-shaped molecules aligned. • Two glass plates, each containing a light polarizer at right angles to the-other plate, sandwich the liquid- crystal material. • Rows of horizontal transparent conductors are built into one glass plate, and columns of vertical conductors are put into the other plate. • The intersection of two conductors defines a pixel position. • ON State: Normally, the molecules are aligned as shown in the "on state" of Fig. Polarized light passing through the material is twisted so that it will pass through the opposite polarizer. The light is then reflected back to the viewer. • OFF State: To turn off the pixel, we apply a voltage to the two intersecting conductors to align the molecules so that the light is not twisted. Liquid Crystal Displays (LCDs)
- 58. Working of Liquid Crystal Displays
- 59. February 17, 2024 Computer Graphics 60 Light wave has two components: 1. Electrical Component 2. Magnetic Component Both of these are mutually perpendicular to each other ie, makes 90 degree angle with each other.
- 60. February 17, 2024 Computer Graphics 61 Polarization of light: means movement of light component in one direction
- 61. February 17, 2024 Computer Graphics 62 Colour Filter: along with transistors and capacitors (attached with colour filter) controls the intensity of light and gives that colour to that light. Electrodes: a conductor through which electricity enters. Certain voltage is applied on these electrodes because of which molecules of crystals twist or untwist
- 62. February 17, 2024 Computer Graphics 63 Cold cathode fluorescent lamps (CCFLs) A backlight is a form of illumination used in liquid crystal displays (LCDs). As LCDs do not produce light by themselves (unlike, for example cathode ray tube (CRT) displays), they need illumination (ambient light or a special light source) to produce a visible image. Liquid Crystals: Nematic liquid crystal produces a 90-degree shift in the polarization of the light passing through when there is no electric field present. When a voltage is applied, an electric field is produced in the liquid, affecting the orientation of the molecules. Nematic comes from a Greek prefix nemato meaning threadlike and is used here because the molecules in the liquid align themselves into a threadlike shape.
- 64. Lecture No. 5: OpenGL (Open Graphics Library)
- 68. OpenGL terrain generator using fractals Terrain is the vertical and horizontal dimension of land surface
- 72. I REPRESENTATION OF OBJECTS ON THE SCREEN - Points, Lines, Curves - Geometrical Objects - Circle - Ellipse - Rectangle - Polygons, Polylines - Transformations – 2D - Windowing and Viewport - Mapping of Objects - Curves and Surfaces - Bezier Curves - Projections - Hidden Surface Removal - Rendering - Light Effects - Shades and Shadows - Textures - Ray Tracing - Illumination
- 73. Goal of standardized software is portability (ie, one thing designed for one system can be used on other system). Also re-writing of code is not required. Number of Graphics software standards came into existence. Some of these are as follows: 1. GKS (Graphics Kernel System) 1984 : First software standard accepted by ISO including ANSI --- First 2D then extended to 3D 2. PHIGS (Programmer’s Hierarchical Interactive Graphics System): • It was extension of GKS. • New features like rendering, colour specifications, picture manipulation were added. 3. GL (Graphics Libraries) by Silicon Graphics Inc. (SGI) • SGI’s Graphics became increasingly popular • They came up with set of routines called GL (Graphics Libraries) • Became popular in Graphics Community • Disadvantage: ….These were platform dependent (On the other hand, OpenGL is platform independent) 4. Open Inventor 5. Virtual Reality Modelling Language (VRML) 6. Java 2D : Create 2D scenes within Java applets 7. Java 3D : Produce 3D web displays 8. RenderMan Interface by Pixar Corporation: Produces scenes by using lightning models 9. Mathematica (provides Graphics Libraries) 10. Matlab (provides Graphics Libraries) 11. Maple (provides Graphics Libraries) III SOFTWARE STANDARDS
- 74. OpenGL (Open Graphics Library) is the computer industry's standard application program interface ( API ) for defining 2-D and 3-D graphic images. OpenGL is a cross-language, multi-platform application programming interface (API) for rendering 2D and 3D vector graphics. OpenGL is designed as a streamlined, hardware- independent interface to be implemented on many different hardware platforms. Tip: An application programming interface (API) is a set of routines, protocols, and tools for building software applications. • This interface consists of about 150 distinct commands that we use to specify the objects and operations needed to produce interactive three- dimensional applications. • With OpenGL, we can build up any desired model from a small set of geometric primitives - points, lines, and polygons. What is OpenGL ?
- 76. • GL (Graphic Library) • Lowest level: vertex, matrix manipulation • Eg:- glVertex3f(point.x, point.y, point.z) • GLU (Graphic Library Utility) • Provides functions/routines for setting up: • Viewing and Projection Matrices • Displaying quadrics and B-Splines • Processing Surface-rendering operations • Helper functions for shapes, transformations • Eg:- gluPerspective( fovy, aspect, near, far ) • GLUT (Graphic Library Utility Toolkit) • Highest level: Window and interface management • Provides library of functions for interacting with any scree-windowing system. • Contains functions for describing quadric curves and surfaces. • Eg:- glutInitWindowSize() OpenGL Hierarchy
- 77. Things used in OpenGL Program: Basic Operations: • Primitive functions – it includes main functions (like - line drawing, polygon, triangle, etc.) • Symbolic Constants • Built-in Data types OpenGL Libraries Header Files For Windows, #include <windows.h> #include <GL/gl.h> #include <GL/glu.h> For Apple OSX systems, #include <GL/glut.h> #include <GLUT/glut.h> Need to create a Window OpenGL program is case sensitive. Eg: We need to write GL in capitals Several system libraries are there…Depends upon the type of computer we are using. Eg: - AppleGL (AGL) – For Apple Systems – Prefix agl - Windows-to-OpenGL (WGL) – For Windows systems - Presentation Manager to OpenGL (PGL) – for IBM OS/2 - Prefix pgl
- 78. PRIMITIVE FUNCTIONS Function names are prefixed with gl and each Component name with a Capital letter Eg: glBegin(with set of primitives) glClear() glEnd() glCopyPixel() glPolygonMode() glBegin(GL_LINES); glVertex2i(180,15); glVertex2i(10,145); glEnd(); • GL_POINTS • GL_LINES • GL_TRIANGLES • GL_QUADS Some Primitives are:
- 79. SYMBOLIC CONSTANTS • Hundreds of symbolic constants are available in OpenGL • Written in CAPITAL letters Eg: GL_2D GL_RGB GL_POLYGON DATA TYPES Special built-in data types are there in OpenGL Eg: GLbyte GLshort GLint GLfloat GLdouble GLboolean
- 80. OpenGL WINDOW To create any graphics display/object using OpenGL, we first need to setup a DISPLAY WINDOW (rectangular area where our picture will be displayed) 100 50 300 400 Monitor Screen OpenGL Display Window
- 81. Writing OpenGL Program: To initialize GLUT: glutInit(&argc, argv); To create Display Window: glutCreateWindow(“My First OpenGL Window”); What a Display Window is to contain? glutDisplayFunc(lineSegment); Display Window is not yet on the screen All Display Windows we have created are activated by using the following function: glutMainLoop(); It must be put at the last in the program argv is a pointer to an array of null terminated strings, and argc says how large this array is. These are automatically passed to you when you start your program and enter main(). argv[0] is a pointer to a string which holds the name of the executable file, including full path. argv[1] is the first argument you pass to you program when starting it, and so on. Like this: c: est.exe hello world Then argc=3 argv[0]=“c: est.exe” argv[1]=“hello” argv[2]=“world”
- 82. Positioning a Window glutInitWindowPosition(50,100); initial Specifying the Window Size: glutInitWindowSize(400, 300); For Display Window, we can choose a background colour (eg. White) : glClearColor(1.0, 1.0, 1.0, 0); R G B Alpha Value 0 = Totally Transparent Object 1 = Opaque Object To actually put display window on screen with the colour values, we need to invoke one more function glClearColor(GL_COLOR_BUFFER_BIT); glClearColor specifies the red, green, blue, and alpha values used by glClear to clear the color buffers. Values specified by glClearColor are clamped to the range [0,1]01.
- 83. Setting Object Color: glColor3f(0.0, 0.4, 0.2); indicates that we are specifying 3 RGB colour components using floating point values glMatrixMode(GL_PROJECTION); gluOrtho2D(0.0, 200.0, 0.0, 150. 0); OpenGL works for 3D To Display Line Segment (say) in 2D, we still have to use 3D viewing operations. For this, we need following two functions: X Values Y Values The glMatrixMode function specifies which matrix is the current matrix.
- 84. #include<iostream> #include<GL/freeglut.h> void init() { glClearColor(0.0, 0.0, 0.0, 0.0); // Set display window colour to white glMatrixMode(GL_PROJECTION); // Set Projection Parameters gluOrtho2D(0.0, 250.0, 0.0, 150.0); //Values of xMin, yMin, xMax, yMax } void Line() { glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0, 1.0, 1.0); glBegin(GL_LINES); glVertex2i(180,15); glVertex2i(10,145); glEnd(); glFlush(); } int main(int argc, char **argv) { glutInit(&argc,argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowSize(400, 300); glutInitWindowPosition(50, 100); glutCreateWindow(“Line Drawing"); init(); glutDisplayFunc(Line); glutMainLoop(); return 0; } OpenGL Program to plot a line Output Bit mask to select a single buffered window. Bit mask to select an RGBA mode window.
- 85. Anoder Code Example void Display() { glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0, 1.0, 0.0); glBegin(GL_POLYGON); glVertex2f(-0.5, -0.5); glVertex2f(-0.5, 0.5); glVertex2f(0.5, 0.5); glVertex2f(0.5, -0.5); glEnd(); glFlush(); } ….