How to Write Plugins?

What is a plugin?

A plugin can be used to add functional logic to the ARPen app. Some example plugin functionalities: draw a line, create a cube, and change texture.

Do you want to write a plugin?

Nice! Start by creating a new swift file in the folder Plugins and create a new class inherited from Plugin. Plugin is a protocol that defines one method and two properties, which are explained below. For now, add your plugin to the PluginManager by opening the file PluginManager.swift and adding the object you had created to the array plugins.

Next, define an identifier and a UIImage for your plugin. These will be used to add your plugin to the menu on the main screen, making it possible to select your plugin. Implement the method didUpdateFrame(scene:buttons:) specified in the Plugin protocol. This method is invoked everytime a new marker position is detected. It is possible that this method is invoked very often — so try to avoid complex computations in this method. The scene elements are children of the "drawingNode" of the penScene.

Where can I find the ARPen's position?

The given PenScene has a SCNNode property named pencilPoint. The position of this node (i.e., penScene.pencilPoint.position) should always be the latest position of the ARPen.

Can I call my plugin with a UIButton?

The plugin menu is automatically populated with the entries of the plugins array in the PluginManager.swift file. Selecting a plugin in the UI activates the selected plugin. Currently, it is not possible to invoke a plugin via events from the ViewController instance. To do so, you need to make changes to ViewController and PluginManager.