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Understanding OpenGL: Core Concepts and Related Libraries for Computer Graphics

This guide provides an overview of OpenGL and its key components, including GLU and GLUT. It covers fundamental concepts such as drawing primitives (points, lines, polygons), data types, and the OpenGL rendering pipeline. The discussion explores various libraries (GLX, WGL, AGL) and utility functions for texture mapping and object space transformations. OpenGL's functionality is explained through common functions and the state machine model. Learn about the attributes and viewing functions, essential for creating stunning graphics in any application.

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Understanding OpenGL: Core Concepts and Related Libraries for Computer Graphics

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  1. CS 470 Introduction to Computer Graphics OpenGL Concepts

  2. Opengl – several related components • OpenGL • glu • glut (freeglut, glow, glutmaster(c++)…) • Others • glx • wgl • apl • pgl • GLUI

  3. gl • 200 functions • Primitives • Geometric • Discrete (bitmaps) • Attribute functions • Viewing functions

  4. glu – Opengl Utility Library • GLU is the OpenGL Utility Library. This is a set of functions to create texture bitmaps from a base image, map coordinates between screen and object space, … • about 17 functions • about 4 drawing primitives

  5. glut – Opengl Utility Toolkit • …a window system independent toolkit for writing OpenGL programs • Generic windows API – • same program/calls work across different gui/windows environments • Provides user interaction functions • mouse, keyboard, menus

  6. Sample Drawing Primitives • gl • Pixels • Bitmaps • Vertice • glu • Cylinder • Disk • Sphere

  7. Sample Drawing Primitives • glut • wire cube / solid cube • wire sphere / solid sphere • wire octahedron / solid octahedron • wire torus / solid torus • wire teapot / solid teapot

  8. OpenGL • Written in C • No overloading of functions • No object oriented programming • but be used from C++

  9. OpenGL Function syntax • glxxxx*() – all opengl functions begin with “gl” • gluxxx*() – all glu functions begin with “glu” • glutxxx*() – all glut functions begin with “glut”

  10. Other libraries syntax • glx – opengl library for X windows • wgl – opengl library for MS Windows • agl – opengl library for Apple Macintosh OS • pgl – opengl library for OS/2 Warp glxCreateWindow() Not same across libraries

  11. OpenGL • general function syntax • glVertex{2|3|4}{s|i|f|d}(TYPE arg1,…); • glVertex{2|3|4}{s|i|f|d}v(TYPE *arg); • glVertex*() manual notation

  12. OpenGL • Data types • standard data types – int, float, double, char • OpenGL types • GLbyte – signed char • GLushort – unsigned short • GLint – int • GLuint – unsigned int • GLfloat – float • GLdouble – double • GLchar – char

  13. OpenGL • Other Data Types – • GLclampf – float from 0.0 to 1.0 • GLsizei – largest nonnegative integer on system • other enumerated GL types • Also some GLU types

  14. OpenGL • OpenGL constants • Predefined constants for setting or testing values • GL_RGB • GL_LINE • GL_POLYGON • GLUT_RGB • GLUT_SINGLE • GLUT_KEY_F1 • GLUT_LEFT_BUTTON • Hundreds of them

  15. OpenGL • OpenGL rendering pipeline • simplified pipeline model Primitive Generation Transform-ation Clipping Projection Rasterization Display

  16. OpenGL as a state machine • OpenGL can be viewed as a state-machine • The action of a function depends on the machines current state • Hundreds of properties (state variables) define the state of OpenGL • A state is in effect until it is changed • glColor3f(1.0,0.0,0.0) • State variables not like object properties

  17. OpenGL Buffers • Frame Buffers • Single • Double

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