Introduction to OpenGL Programming

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Introduction to OpenGL Programming

• Jian-Liang Lin
• 2002

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What is OpenGL? -1

• OpenGL is a cross-platform standard for 3D
  rendering. and software interface to graphics
  hardware.
• The OpenGL Architecture Review Board(ARB), and
  independent consortium formed in 1992, governs
  the OpenGL specification.
• OpenGL routines use the prefix gl.

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What is OpenGL? -2

• Designed as a hardware-independent interface and
  implemented on many different hardware platforms.
  
• No commands for performing windowing tasks or
  obtaining user input are included in OpenGL.
• You must work through whatever windowing system
  controls the particular hardware you're using.

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What is OpenGL? -3

• OpenGL doesn't provide high-level commands for
  describing models of three-dimensional objects.
• With OpenGL, you must build up your desired model
  from a small set of geometric primitives.
• points, lines, triangles, and polygons etc.

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The Advantages of OpenGL

• Industry standard
• Fast
• Portable
• Easy to use
• Well-documented

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OpenGL rendering pipeline
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Color Models

• RGBA color
• Red, Green, Blue, and Alpha channels
• Up to 16M colors
• Color-indexed
• Small numbers of colors accessed by indices from
  a color lookup table(palette)
• 8 bits 256 colors

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Basic Features

• Transformation
• Materials Lighting Smooth Shading
• Texture mapping
• Depth buffer test (Z-Buffer)
• Alpha blending
• Double buffering for animation
• Pixel operations

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OpenGL Buffering -1

• OpenGL supports a variety of buffers for advanced
  rendering
• Depended on driver implementation
• Color buffers
• Front-left, front-right, back-left, back-right,
  and any number of auxiliary buffers
• Depth buffer
• Also known as Z-Buffer for HSR

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OpenGL Buffering -2

• Alpha buffer
• Blending
• Stencil buffer
• To restrict drawing to certain portions of the
  screen. (basic application)
• Accumulation buffer
• Full scene manipulation

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API Hierarchy
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OpenGL library -1

• SGIs OpenGL SDK
• OpenGL.DLL GLU.DLL
• Open source implementation for hardware vendor
  reference.
• Best software rendering library.
• Can be downloaded from SGIs website.

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OpenGL library -2

• Microsofts implementation
• From Win95 OSR2, Microsoft Windows ship with
  OpenGL32.DLL.
• For old Win95 users, you still can download
  OPENGL95.EXE via Microsoft website.
• Header files and import library files are already
  included in Win32 Platform SDK.

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OpenGL library -3

• Microsofts OpenGL32.DLL applies a hardware
  accelerated driver registered in Registry.
• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows
  NT\CurrentVersion\OpenGLDrivers
• You can search it by using REGEDIT.EXE

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Mesa Graphics Library

• A OpenGL clone library.
• You can use it as using OpenGL.
• Portable on many OS.
• You can download it in the following website
• http//www.mesa3d.org/

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OpenGL Utility Library

• The OpenGL Utility Library(GLU) provides many of
  the modeling features, such as quadric surfaces
  and NURBS curves and surfaces.
• GLU is a standard part of every OpenGL
  implementation
• GLU routines use the prefix glu.
• gluLookAt( )

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Windows system related helper library

• For every window system, there is a library that
  extends the functionality of that window system
  to support OpenGL rendering.
• X Window System -gt GLX
• Microsoft Windows -gt WGL
• IBM OS/2 -gt PGL

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OpenGL Utility Toolkit -1

• The OpenGL Utility Toolkit (GLUT) is a window
  system-independent toolkit, written by Mark
  Kilgard, to hide the complexities of differing
  window system APIs.
• GLUT routines use the prefix glut.
• glutPostRedisplay()

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OpenGL Utility Toolkit -2

• You can download this toolkit in the following
  website
• http//reality.sgi.com/mjk_asd/glut3/glut3.html
• We focus on this toolkit.

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Programming Environment -1

• PC(X86)
• OpenGL v1.1 software runtime is included as part
  of operating system for Win 2000, Windows 98,
  Windows 95 (OSR2) and Windows NT
• Linux, FreeBSD, other UNIX-like OS can use Mesa
  graphics library.

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Programming Environment -2

• SGI workstation
• Personal IRIS, Indigo, Indy, Indigo2 O2,
• Octane in CGGM Lab.
• All with IRIS Operating System and X Window System

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Compilers Microsoft Visual C

• Start a new workspace of Win32 Console
  application.
• Add OpenGL32.lib glu32.lib glut32.lib in
  Projects/Setting/Link/Library modules column for
  linking

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Compilers Unix-like OS

• Library files needed
• libGL.so, libGLU.so, libglut.a, libX11.a,
  libX11.so etc
• Command line
• gcc source files o output file lglut lGLU
  lGL lX11 lm
• The ordering of the linking flags is not
  changeable.
• Suggest to write a Makefile.

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Where is the reference?

• OpenGL official site
• http//www.opengl.org
• You refer to OpenGL API documentation in MSDN
  Library.

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How can you start?

• Choose your platform
• Get your desire OpenGL related library.
• Start a GLUT simple program, build and test.
• Refine the code as you wish.
• Refer to some reference materials.
• Consult with TA ?
• Feel happy to see the result.

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Any Question?

• ?