Chapter 4. Application Authoring Basics

Chapter 4. Application Authoring Basics
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Table of Contents

Basic Application Information
Draw Manager-Specific Application Classes

How to Get Input
Where to Get Input
Tutorial: Getting Input

In this chapter, we build upon the information presented in the previous chapters to explain the basics of writing VR Juggler applications. This information will apply to all applications regardless of the graphics programming interface used to render the immersive space. Understanding this chapter will be critical in being able to write effective, portable VR Juggler applications.

Application Review

Before getting into too much detail, we present this section as a review from earlier chapters. There is no new information here; it is simply a quick overview of the basics of VR Juggler applications.

Basic Application Information

As described in previous chapters (see Chapter 1, Getting Started, for example), all VR Juggler applications derive from a base application object class (vrj::App). This class defines the basic interface that VR Juggler expects from all application objects. This means that when constructing an application, the user-defined application object must inherit from vrj::App or from a Draw Manager-specific application class that has vrj::App as a superclass. For example:

class userApp : public vrj::App
{
public:
   init();
   preFrame();
   postFrame();
}

This defines a new application class (userApp), instances of which can be used anywhere that VR Juggler expects an application object.

Draw Manager-Specific Application Classes

A user application does not have to (and in most cases does not) derive from vrj::App directly. In almost all cases, an application class is derived from a Draw Manager-specific application class. For example:

class userGlApp : public vrj::GlApp
{
public:
   init();
   preFrame();
   postFrame();
   
   draw();
}

This is an example of an OpenGL application. The application class (userGlApp) has derived directly from the OpenGL Draw Manager-specific vrj::GlApp application base class. This class provides extra definitions in the interface that are custom for OpenGL applications.