Editing Simulation Extensions

By using OpenRocket's extension and listener mechanism, it's possible to modify the program itself to add features that are not supported by the program as distributed; some extensions that have been created already provide the ability to air-start a rocket, to add active roll control, and to calculate and save extra flight data.

This page will discuss extensions and simulations.  We'll start by showing how a simulation is executed (so you can get a taste of what's possible), and then document the process of creating the extension.  '''WARNING: writing an extension inserts new code into the program. It is entirely possible to disrupt a simulation in a way that invalidates simulation results, or can even crash the program.  Be careful!'''

== Adding an Extension to a Simulation ==
Extensions are added to a simulation through a menu in the "Simulation Options" tab.
# Open a .ork file and go to the '''Flight Simulations''' tab
# Click the ''Edit simulation'' button to open the '''Edit simulation''' dialog.
# Go to the '''Simulation options''' tab.
# Click the '''Add extension''' button
This will open a menu similar to the one in the following screenshot:

[[File:Extension-menu.png]]

Clicking on the name of an extension will add it to the simulation; if it has a configuration dialog the dialog will be opened:

[[File:Air-start-configuration.png]]

In the case of the air-start extension, the configuration dialog allows you to set the altitude and velocity at which your simulation will begin.  After you close the configuration dialog (if any), a new panel will be added to the '''Simulation options''' pane, showing the new extension with buttons to reconfigure it, obtain information about it, or remove it from the simulation:

[[File:Air-start-pane.png]]

== Writing Simulation Extensions and Listeners ==
The remainder of this page will discuss the process for writing simulation extensions and listeners.  It is expected that the reader will be familiar with programming in Java.

Creating an extension for OpenRocket requires writing three classes:
- A listener, which extends <code>AbstractSimulationListener</code>,
- An extension, which extends <code>AbstractSimulationExtension</code>, and
- A provider, which extends <code>AbstractSimulationExtensionProvider</code>.