OpenSceneGraph 3.0: Beginner's Guide

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.

OpenSceneGraph 3.0

Credits

Foreword

About the Authors

Acknowledgement

About the Reviewers

www.PacktPub.com

Preface

Free Chapter

The Journey into OpenSceneGraph

A quick overview of rendering middleware

Scene graphs

The Birth and development of OSG

Time for action—say "Hello World" OSG style

Live in community

Summary

Compilation and Installation of OpenSceneGraph

System requirements

Using the installer

Time for action—installing OSG

Running utilities

Time for action—playing with osgviewer

Using the project wizard

Time for action—creating your solution with one click

Prebuilts making trouble?

Cross-platform building

Starting CMake

Time for action—running CMake in GUI mode

Setting up options

Generating packages using Visual Studio

Time for action—building with a Visual Studio solution

Generating packages using gcc

Time for action—building with a UNIX makefile

Configuring environment variables

Summary

Creating Your First OSG Program

Constructing your own projects

Time for action—building applications with CMake

Using a root node

Time for action—improving the "Hello World" example

Understanding memory management

ref_ptr<> and Referenced classes

Collecting garbage: why and how

Tracing the managed entities

Time for action—monitoring counted objects

Parsing command-line arguments

Time for action—reading the model filename from the command line

Tracing with the notifier

Redirecting the notifier

Time for action—saving the log file

Summary

Building Geometry Models

How OpenGL draws objects

Geode and Drawable classes

Rendering basic shapes

Time for action—quickly creating simple objects

Storing array data

Vertices and vertex attributes

Specifying drawing types

Time for action—drawing a colored quad

Indexing primitives

Time for action—drawing an octahedron

Using polygonal techniques

Time for action—tessellating a polygon

Rereading geometry attributes

Customizing a primitive functor

Time for action—collecting triangle faces

Implementing your own drawables

Using OpenGL drawing calls

Time for action—creating the famous OpenGL teapot

Summary

Managing Scene Graph

The Group interface

Managing parent nodes

Time for action—adding models to the scene graph

Traversing the scene graph

Transformation nodes

Understanding the matrix

The MatrixTransform class

Time for action—performing translations of child nodes

Switch nodes

Time for action—switching between the normal and damaged Cessna

Level-of-detail nodes

Time for action—constructing a LOD Cessna

Proxy and paging nodes

Time for action—loading a model at runtime

Customizing your own NodeKits

Time for action—animating the switch node

The visitor design pattern

Visiting scene graph structures

Time for action—analyzing the Cessna structure

Summary

Creating Realistic Rendering Effects

Encapsulating the OpenGL state machine

Attributes and modes

Time for action—setting polygon modes of different nodes

Inheriting render states

Time for action—lighting the glider or not

Playing with fixed-function effects

Time for action—applying simple fog to models

Lights and light sources

Time for action—creating light sources in the scene

The Image class

The basis of texture mapping

Time for action—loading and applying 2D textures

Handling rendering order

Time for action—achieving the translucent effect

Understanding graphics shaders

Using uniforms

Time for action—implementing a cartoon cow

Working with the geometry shader

Time for action—generating a Bezier curve

Summary

Viewing the World

From world to screen

The Camera class

Rendering order of cameras

Time for action—creating an HUD camera

Using a single viewer

Digging into the simulation loop

Time for action—customizing the simulation loop

Using a composite viewer

Time for action—rendering more scenes at one time

Changing global display settings

Time for action—enabling global multisampling

Stereo visualization

Time for action—rendering anaglyph stereo scenes

Rendering to textures

Frame buffer, pixel buffer, and FBO

Time for action—drawing aircrafts on a loaded terrain

Summary

Animating Scene Objects

Taking references to functions

List of callbacks

Time for action—switching nodes in the update traversal

Avoiding conflicting modifications

Time for action—drawing a geometry dynamically

Understanding ease motions

Animating the transformation nodes

Time for action—making use of the animation path

Changing rendering states

Time for action—fading in

Playing movies on textures

Time for action—rendering a flashing spotlight

Creating complex key-frame animations

Channels and animation managers

Time for action—managing animation channels

Loading and rendering characters

Time for action—creating and driving a character system

Summary

Interacting with Outside Elements

Various events

Handling mouse and keyboard inputs

Time for action—driving the Cessna

Adding customized events

Time for action—creating a user timer

Picking objects

Intersection

Time for action—clicking and selecting geometries

Windows, graphics contexts, and cameras

The Traits class

Time for action—configuring the traits of a rendering window

Integrating OSG into a window

Time for action—attaching OSG with a window handle in Win32

Summary

Saving and Loading Files

Understanding file I/O plugins

Discovery of specified extension

Supported file formats

The pseudo-loader

Time for action—reading files from the Internet

Configuring third-party dependencies

Time for action—adding libcurl support for OSG

Writing your own plugins

Handling the data stream

Time for action—designing and parsing a new file format

Serializing OSG native scenes

Creating serializers

Time for action—creating serializers for user-defined classes

Summary

Developing Visual Components

Creating billboards in a scene

Time for action—creating banners facing you

Creating texts

Time for action—writing descriptions for the Cessna

Creating 3D texts

Time for action—creating texts in the world space

Creating particle animations

Time for action—building a fountain in the scene

Creating shadows on the ground

Time for action—receiving and casting shadows

Implementing special effects

Time for action—drawing the outline of models

Playing with more NodeKits

Summary

Improving Rendering Efficiency

OpenThreads basics

Time for action—using a separate data receiver thread

Understanding multithreaded rendering

Time for action—switching between different threading models

Dynamic scene culling

Occluders and occludees

Time for action—adding occluders to a complex scene

Improving your application

Time for action—sharing textures with a customized callback

Paging huge scene data

Making use of the quad-tree

Time for action—building a quad-tree for massive rendering

Summary

Pop quiz—Answers

Index

Customer Reviews

5 star

4 star

3 star

2 star

1 star

Time for action—generating a Bezier curve

OpenGL has provided functions to generate Bezier and NURBS curves and surfaces for years, but they are not as good as we wish. Today's geometry shader can do the same work in a more convenient and efficient way. Take the generation of a Cubic Bezier curve as an example. Given two endpoints, and two control points to the shader, it will then produce a smooth curve, with specific segments, that begins and ends at two different endpoints, and be pulled away towards the control points.

Include the necessary headers. We'd like to change the output line width, so the osg::LineWidth class is used here, too:
```
#include <osg/Program>
#include <osg/LineWidth>
#include <osgDB/ReadFile>
#include <osgViewer/Viewer>
```

The vertex shader is always required. But this time it only transforms vertices to successive shaders:

static const char* vertSource = {
    "#version 120\n"
    "#extension GL_EXT_geometry_shader4 : enable\n"
    "void main()\n...

OpenSceneGraph 3.0: Beginner's Guide

OpenSceneGraph 3.0: Beginner's Guide

Overview of this book

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OpenSceneGraph 3.0: Beginner's Guide

Time for action—generating a Bezier curve