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computer graphics

computer graphics. TA: Nouf Al- harbi. NoufNaief.net nouf200@hotmail.com. What’s Computer Graphics..?. Image Description. Computer. Computer Graphics. How we look at an image!. Color: B/W or color (RGB) Frame: length, width Size: length, width, area, height and volume if 3D

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computer graphics

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  1. computer graphics TA: Nouf Al-harbi NoufNaief.net nouf200@hotmail.com

  2. What’s Computer Graphics..? Image Description Computer Computer Graphics

  3. How we look at an image! • Color: B/W or color (RGB) • Frame: length, width • Size: length, width, area, height and volume if 3D • Type: Static or animated • Content: The scene: Objects, characters • Background/ Foreground • lighting, shading • Textures • Viewing angle: camera location

  4. How The computer see an image! • The computer generally sees an image as a set of square points or PIXELS (Picture Elements) • Each Pixel having a defined RGB color • These pixels and their colors are processed to extract information about the image content

  5. Introductiom to OpenGL Computer Graphics LAB Objective To give you a good practical experience in programming graphics using C++ and OpenGL

  6. Introductiom to OpenGL LAB Marks

  7. Introductiom to OpenGL Lab Materials .. NoufNaief.net

  8. Computer graphicslab 1 Introduction to OpenGL

  9. Introductiom to OpenGL objectives • By the end of this lab you will be able to know : • What’s OpenGl ..? • What does it do ? And what doesn’t it do..? • What’s GLUT and why do we use it ..? • Write the 1st OpenGL program

  10. Introductiom to OpenGL What is OpenGL? • OpenGL stands of Open Graphical Library • It is a software interface to graphics hardware. • It consists of about 120 distinct commands • to specify the objects and operations needed to produce interactive 3D applications • It is developed by many companies and it is free to use • You can develop OpenGL-applications without Licensing • OpenGL is a system-independent interface • it can work with any programming language and any operating system

  11. Introductiom to OpenGL What I can do with OpenGL ..? • This picture may give you an idea of the kinds of things you can do with the OpenGL graphics system • This picture is the cover of the ‘Red Book’: OpenGl Programming user guide

  12. Introductiom to OpenGL What OpenGL doesn’t do ?

  13. Introductiom to OpenGL The support libraries GLU and GLUT

  14. Introduction to OpenGL GLUT • The OpenGL UtilityToolkit (GLUT) is a Programming interface • It implements a simple windowing application programming interface (API) for OpenGL • The toolkit supports the following functionality : • Create Display windows. • Interactive with input devices and detect user input. • An “idle” routine and timers. • Utility routines to generate various solid and wire frame objects.

  15. Introductiom to OpenGL GLU • GLU: OpenGL Utility Library • provides functions for drawing more complex primitives than those of OpenGL • such as curves and surfaces

  16. Introductiom to OpenGL OpenGL Basics • Function names: • Begins with gl . • Each component word starts with capital letter. • Examples: • glClear( ) • glClearColor( )

  17. Introductiom to OpenGL OpenGL Basics • Basic Constants: • Starts with GL • Component words are written in Capital letters and separated by underscore ( _ ). • Examples: • GL_COLOR_BUFFER_BIT • GL_POINTS • GL_LINES

  18. Introductiom to OpenGL OpenGL Basics • All the functions in GLUT starts with glut • All the functions in GLU starts with glu

  19. Introductiom to OpenGL your first OpenGL Program • Preparing the graphics work environment • We will use VC++ • You need to include these files to your computer

  20. your first OpenGL ProgramGenerate a square on a solid background • Open VC++ • New  source file • Write the following code • Compile and build it

  21. Introductiom to OpenGL your first OpenGL Program • You have to link used libraries to your project • Select Project/Settings from the main menu. • A dialog box appears, select the Link tab. • Add the following files to the Object/library modules: opengl32.lib glut32.lib glu32.lib

  22. Introductiom to OpenGL your first OpenGL Program • To write OpenGL program, we must include these files • glut. h • glu. h • gl. h • #include <GL/glut.h> should automatically include the others

  23. Introductiom to OpenGL your first OpenGL Program • There are 2 functions in our program • Display function • Main function • Each of them calls a number of OpenGL/glut functions 1 2

  24. Introductiom to OpenGL Main Function Commands • Initializes GLUT • should be called before any OpenGL command • takes the arguments from main()

  25. Introductiom to OpenGL Main Function Commands • Creates a window on the screen with the title • Parameters: • Title of the window would be created • Returns an integer that can be used to refer to the window in multi-window situations.

  26. Introductiom to OpenGL Main Function Commands In order to respond to the input event, the application must provide a function – known as a callback function – to handle the event; OpenGL automatically calls the application’s function, passing it the event data. • The function display() is called each time there is a display callback • Parameters: • A function that contains what we want to draw in the screen

  27. Introductiom to OpenGL Main Function Commands • Causes the program to enter an event-processing loop • Once called, this routine will never return. • It will call as necessary any callbacks that have been registered. • This statement should be the last one in the main() function

  28. Introductiom to OpenGL Display Function Commands • called by GLUT when the window is redrawn. • we should specify what we want to output to screen.

  29. Introductiom to OpenGL Display Function Commands OpenGL doesn’t draw its graphics directly to the window. It actually draws into a data structure (an array of pixels) inside OpenGL called the frame-buffer. Periodically, OpenGL copies the pixels in the frame buffer into the window. • clears one or more of OpenGL’s buffers. • When glClear() is called, each pixel in the buffer is set to the current clear color, which is set to black by default. • Parameters: • GL_COLOR _BUFFER_BIT: • frame buffer, which holds the pixels which will be copied to the window

  30. Introductiom to OpenGL Display Function Commands • Specifies the beginning of an object of type mode • Modes include: • GL_POINTS • GL_LINES • GL_POLYGON , …etc.

  31. Introductiom to OpenGL Display Function Commands glVertex{234}{sifd}(X_coordinate, Y_coordinate,...) • {234} Specifies the location of a vertex in two, three, or four dimensions with the types short (s), int (i), float (f), or double (d)

  32. Introductiom to OpenGL (0,1) x (1,0) (-1,0) (0,0) (0, -1)

  33. Introductiom to OpenGL Display Function Commands • Specifies the end of a list of vertices.

  34. Introductiom to OpenGL Display Function Commands • instructs OpenGL to make sure the screen is up to date. • it causes the contents of any internal OpenGL buffers are “flushed” to the screen

  35. Introductiom to OpenGL REFERENCES: • Materials of this lab are prepared using: • An Introduction to Graphics Programming with OpenGL by : Toby Howard, School of Computer Science, University of Manchester • Lighthouse3d: http://www.lighthouse3d.com/opengl/glut/index.php?1 • OpenGL Programming Guide 'The Red Book’ • Computer Graphics Lab -1st semester – 2010-2011 by : Ins. Ruwaida Al-harbi & Ins. Nouf Al-harbi • Computer Graphics Lectures – 1st semester 2009-2010 by Dr.AhmedGhali

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