Book Image

OpenSceneGraph 3.0: Beginner's Guide

Book Image

OpenSceneGraph 3.0: Beginner's Guide

Overview of this book

Virtual reality has quite a lot of demand in computer science today and OpenSceneGraph, being one of the best 3D graphics toolkits, is being used widely. Although you can use the powerful OpenSceneGraph, based on the low-level OpenGL API, to implement virtual-reality applications that simulate different environments in the 3D world, developing picture-perfect applications is easier said than done.This book has been written with the goal of helping readers become familiar with the structure and main functionalities of OpenSceneGraph (OSG), and guide them to develop virtual-reality applications using this powerful 3D graphics engine. This book covers the essence of OpenSceneGraph (OSG), providing programmers with detailed explanations and examples of scene graph APIs.This book helps you take full advantages of the key features and functionalities of OpenSceneGraph (OSG). You will learn almost all of the core elements required in a virtual reality application, including memory management, geometry creation, the structure of the scene graph, realistic rendering effects, scene navigation, animation, interaction with input devices and external user interfaces, file reading and writing, and so on. With the essential knowledge contained in this book, you will be able to start using OSG in your own projects and research fields, and extend its functionalities by referring to OSG's source code, official examples and API documentation. This handy book divides the core functionalities of the proved and comprehensive OpenSceneGraph (OSG) 3D graphics engine into different aspects, which are introduced in separate chapters. Each chapter can be treated as an individual part that covers one important field of OSG programming, along with several examples illustrating concrete usages and solutions. But the sequence of chapters is also organized from the easy to the more difficult, to help you get to grips with OSG.By the end of the whole book, you will have gained a ready-to-use OSG development environment for yourself and have the general ability to develop OSG-based applications and extend practical functionalities for your own purposes.
Table of Contents (22 chapters)
OpenSceneGraph 3.0
About the Authors
About the Reviewers

Time for action—say "Hello World" OSG style

Can't wait to have a taste of OSG programming? Here is the simplest example, which shows how to load an existing model file and render it on the screen. It is much more interesting than just printing a "Hello World" text on the console:

  1. Create a new project with any source code editor:

    #include <osgDB/ReadFile>
    #include <osgViewer/Viewer>
    int main( int argc, char** argv )
        osgViewer::Viewer viewer;
        viewer.setSceneData( osgDB::readNodeFile("cessna.osg") );
  2. Specify the OSG header location and dependent libraries. You need to tell the linker to link your project with five libraries: OpenThreads, osg, osgDB, osgUtil, and osgViewer. You will learn more about configuring an OSG application in the next chapter.

  3. Build your project. Make sure the file cessna.osg already exists in the same directory as the executable file, or in the path specified with the OSG_FILE_PATH environment variable.

  4. Check it out! You get a full-screen display with a flight model shown in the middle:

  5. Try to make some changes to what you are observing simply with your mouse. Press and hold the left, middle, and right mouse buttons when you are moving the mouse, to rotate, move, and scale the Cessna. Note that you are not actually modifying the model but changing the virtual view point instead.

What just happened?

An easy-to-read example was just created to show how powerful and clear OSG is. The osgDB::readNodeFile() function is used to read an existing node file, that is, a scene graph that represents the Cessna model. The osgViewer::Viewer instance is then created to set the scene data and provide a simulation loop for the application.

Here, osgDB and osgViewer are namespaces, and Viewer is a class name. The naming style of a function or class member uses the same convention as the famous "camel-case", that is, the first word of the function name starts with a lowercase letter, and additional ones start with upper-case letters.