Creating an Engine

• Overview
• Defining Inputs and Outputs
• Initializing the Engine Class
• Defining the Constructor
• Implementing an evaluate() Method
• Creating a Simple Engine
• Dealing with Multiple-Value Fields
• Notification and Evaluation
• Creating a New Field Converter

This chapter describes how to create new subclasses of SoEngine. New concepts introduced in this chapter include how notification of changes in field data propagates through the scene graph and how to block notification if desired. Be sure you are familiar with Engines before you continue in this chapter.

The first part of this chapter offers an overview of the steps required to create a new engine. When necessary, additional sections explain key concepts in further detail and list the relevant macros. Chapter examples show how to create six engine classes:

• A simple engine called MultFloatVec3f
• An engine with multiple inputs called SoComposeVec2f
• An engine with multiple outputs called SoDecomposeVec2f
• An engine that simulates fanning in of multiple connections called FanIn
• An engine that controls propagation of its output value called Ticker
• A field converter engine called ConvertSFShortToSFFloat