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<h2>Introduction to the OpenSceneGraph</h2>

<p>Welcome to OpenSceneGraph project!
</p>
<p>In this document I'll introduce what a scene graph is, what the OpenSceneGraph project encompasses, and provide tips on how to learn how to use it
and to contact or contribute to the OpenSceneGraph community.
</p>

<i><NAME>,
Project Lead.
April 2002.</i>

<hr>

<h2>What is a Scene Graph?</h2>
</p>Its a tree! Quite simply one the best and most reusable datastructures invented.Typically drawn schematically as
root at the top, leaves at the bottom. It all starts with a topmost root node which
encompasses your whole virtual world, be it 2D or 3D. The world is then broken down
into hierachy of nodes represent either a spatial grouping of objects,
set the position of or animate objects,. or define a logical relationship between objects such as to manage
the various states of a traffic light.The leaves of the graph represent the phyical objects
themselves, the drawable geometry and their material properties.
</p>

<hr>

<h2>Why use a Scene Graph - Performance, Productivity, Portability and Scalability.</h2>

</p><i>Performance</i> - scene graphs provide an excellent framework for maximize graphics
performance. A good scene graph employs two key techinques - culling of the objects that won't
be seen on screen, and state sorting of properties such as textures and materials
so that all similar objects are drawn together. Without culling the CPU, buses and
GPU will all become swamped by many times the amount of data tham they acual require.to represent
you work accurately. The hierachical structure of the scene graph makes this culling
process.very efficient.with whole town being culled with just a few operations! Without state storting, the the buses and GPU will thrash between
states, stalling the graphics and destroying graphisc throughout.  As GPU's get faster and faster, the cost of
stalling the graphics is also going up, so scene graph are become ever more important.
</p>

</p><i>Productivity</i> - scene graphs take much of the hardwork required to develop
high perftomance graphics applications. The scene graphs manage all the graphics for you,
reducing what would be thousands of lines of OpenGL down to a few simple calls..Furthermoe,
one of most powerfukl concepts in Object Orientated programming is that of object
compotsition, enshrined in <i>Composite Design Pattern</i>, which fits the scene graph
tree strucutre perfectly which makes it highly flexible and reusable design - in real terms
this means that it can be easily adapted it to solve your problems. Scene graph also often come
additional utilitie libraries which range for helping users set up and manage graphics
windows to import of 3d modes and images.  All this together allows the user to achieve
a great deal with very little coding.A dozen lines of code can be enough to load your data
and create an interactive viewer!
</p>

</p><i>Portability</i> - scene graphs encapsulate much of the lower level tasks of rendering
graphics and reading and writing data, reducing or even eradicating the platform specific
coding that you require in your own application. If the underlying scene graph is portable
then moving from platform to platform can be a simple as recompiling your source code.
</p>

</p><i>Scalability</i> - along with being able to dynamic manage the complexity of scenes
automatically to account for differences in graphics performance across a range of machines,
scene graphs also make it much easier to manage complex hardware configurations, such as clusters
of graphics machines, or multiprocessor/multipipe systems such as SGI's Onyx. A good scene graph
will allow the developer to concentrate on developing their own application while rendering
framework of the scene graph handles the differnt underlying hardware configurations.
</p>

<hr>

<h2>What the OpenSceneGraph encompasses?</h2>

<hr>
<commit_msg>updated the introduction.html, still not complete but getting there. No edited for typo's yet :-)<commit_after><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<html>
<head>
  <title>introduction to the OpenSceneGraph</title>
</head>
<body bgcolor="white">

<img src="OpenSceneGraphBanner_Distribution.jpg" width=640 height=77 border=0>

<h2>Introduction to the OpenSceneGraph</h2>

<p>Welcome to OpenSceneGraph project!
</p>
<p>The OpenSceneGraph is an Open Source, Cross Platform (Widows, Linux, Mac OSX, FreeBSD, Irix, Solaris),
Standard C++ and OpenGL based graphics development library, uses range from visual simulation, games,
virtual reality, sceintific visualization and graphics research. This pages introduces a
what scene graphs are, why graphics developers use them, and details about the OpenSceneGraph,
project, how to learn how to use it and contribute to the OpenSceneGraph community.
</p>

<i><NAME>,
Project Lead.
April 2002.</i>

<hr>

<h2>What is a Scene Graph?</h2>
</p>Its a tree! Quite simply one the best and most reusable datastructures invented.Typically drawn schematically as
root at the top, leaves at the bottom. It all starts with a topmost root node which
encompasses your whole virtual world, be it 2D or 3D. The world is then broken down
into hierachy of nodes representing either a spatial grouping of objects,
setting the position of objects, animating objects,. or define a logical relationship between objects such as to manage
the various states of a traffic light.The leaves of the graph represent the phyical objects
themselves, the drawable geometry and their material properties.
</p>

</p>A scene graph isn't a complete game or simulation engine, although may be one of the main
components of such an engine, it's primary focus is representing your 3d worlds, and rendering it efficiently.  Physics models, collision detection and audio are left to other development libraries that a user will
integrate with.. The fact that scene graphs don't typically integrate all these features
is actually a really good thing, it aids interoprability with clients own applications
and tools they wish to use and allows them to serve many varied markets from games, visual
simulation, virtual reality, scientific and commerical visulasation, training thruogh to modelling
programs.
</p>

<hr>

<h2>Why use a Scene Graph - Performance, Productivity, Portability and Scalability.</h2>

</p><i>Performance</i> - scene graphs provide an excellent framework for maximize graphics
performance. A good scene graph employs two key techinques - culling of the objects that won't
be seen on screen, and state sorting of properties such as textures and materials
so that all similar objects are drawn together. Without culling the CPU, buses and
GPU will all become swamped by many times the amount of data tham they acual require.to represent
you work accurately. The hierachical structure of the scene graph makes this culling
process.very efficient.with whole town being culled with just a few operations! Without state storting, the the buses and GPU will thrash between
states, stalling the graphics and destroying graphisc throughout.  As GPU's get faster and faster, the cost of
stalling the graphics is also going up, so scene graph are become ever more important.
</p>

</p><i>Productivity</i> - scene graphs take much of the hardwork required to develop
high perftomance graphics applications. The scene graphs manage all the graphics for you,
reducing what would be thousands of lines of OpenGL down to a few simple calls..Furthermoe,
one of most powerfukl concepts in Object Orientated programming is that of object
compotsition, enshrined in <i>Composite Design Pattern</i>, which fits the scene graph
tree strucutre perfectly which makes it highly flexible and reusable design - in real terms
this means that it can be easily adapted it to solve your problems. Scene graph also often come
additional utilitie libraries which range for helping users set up and manage graphics
windows to import of 3d modes and images.  All this together allows the user to achieve
a great deal with very little coding.A dozen lines of code can be enough to load your data
and create an interactive viewer!
</p>

</p><i>Portability</i> - scene graphs encapsulate much of the lower level tasks of rendering
graphics and reading and writing data, reducing or even eradicating the platform specific
coding that you require in your own application. If the underlying scene graph is portable
then moving from platform to platform can be a simple as recompiling your source code.
</p>

</p><i>Scalability</i> - along with being able to dynamic manage the complexity of scenes
automatically to account for differences in graphics performance across a range of machines,
scene graphs also make it much easier to manage complex hardware configurations, such as clusters
of graphics machines, or multiprocessor/multipipe systems such as SGI's Onyx. A good scene graph
will allow the developer to concentrate on developing their own application while the rendering
framework of the scene graph handles the differnt underlying hardware configurations.
</p>

<hr>

<h2>So what about the OpenSceneGraph project?</h2>

<p>
The OpenSceneGraph is Open Source, all the source to is published under the
GNU Library General Public License (LGPL) which allows both open source and closed source
projects to use, modify and distribute it freely as long its usage complies with the
LGPL. The project has been developed over the last four years, initliated by <NAME>, and
then taken over by <NAME> who leads the continues to lead project, there are many
other contributors to the library, for a full list check out the AUTHORS file. Both Robert
and Don now work on the OpenSceneGraph in a professional capaciity provide consultancy
and bespoke developments ontop the library, and are also colloborating on the book.Work on
the core scene graph and support of public mailing list remains unpaid as are the
contributions of the rest of the communinity, but this hasn't impacted the quality of the
source or support which once you get stuck in you grow to appreciate.
</p>

<p>
The project itself is written entitely in Standard C++ and OpenGL, makes full use of STL
and Design Patterns, and leverages the open source development model to provide clean, highly portable,
and flexible scene graph. The project is current in alpha, which means part of the API are still to be
developerd, or subjec to change, but the vast majority of the scene graph is there, and a beta will
be published within the next few months, wiht a 1.0 release in late summer. Despite the
alpha development status, the project has alrady earned the reputation as one of the leading
open source scene graph, and is establishing itself a vialbe alternative to the commericial
scene graphs. Numerous companies, university researchers and graphics enthusasts have
already adopted their project, and a from all over the world.</p>

<hr>

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