Overview#

This extension is based on the omni.graph.template.python template extension for creating a Kit extension that contains only Python OmniGraph nodes.

The Files#

The convention of having implementation details of a module in the _impl/ subdirectory is to make it clear to the user that they should not be directly accessing anything in that directory, only what is exposed in the __init__.py.

The Build File#

Kit normally uses premake for building so this example shows how to use the template premake5.lua file to customize your build. By default the build file is set up to correspond to the directory structure shown above. By using this standard layout the utility functions can do most of the work for you.

lightspeed.trex.logic.ogn/premake5.lua

By convention the installed Python files are structured in a directory tree that matches a namespace corresponding to the extension name, in this case omni/graph/template/python/, which corresponds to the extension name the extension name, in this case lightspeed/trex/logic/ogn/, which corresponds to the extension name lightspeed.trex.logic.ogn. You’ll want to modify this to match your own extension’s name. Changing the first highlighted line is all you have to do to make that happen.

The Configuration#

Every extension requires a config/extension.toml file with metadata describing the extension to the extension management system. Below is the annotated version of this file, where the highlighted lines are the ones you should change to match your own extension.

Contained in this file are references to the icon file in data/icon.svg and the preview image in data/preview.png which control how your extension appears in the extension manager. You will want to customize those.

Documentation#

Everything in the docs/ subdirectory is considered documentation for the extension.

README.md The contents of this file appear in the extension manager window so you will want to customize it. The location of this file is configured in the extension.toml file as the readme value.
CHANGELOG.md It is good practice to keep track of changes to your extension so that users know what is available. The location of this file is configured in the extension.toml file as the changelog value, and as an entry in the [documentation] pages.
Overview.md This contains the main documentation page for the extension. It can stand alone or reference an arbitrarily complex set of files, images, and videos that document use of the extension. The toctree reference at the bottom of the file contains at least GeneratedNodeDocumentation/, which creates links to all of the documentation that is automatically generated for your nodes. The location of this file is configured in the extension.toml file in the [documentation] pages section.
directory.txt This file can be deleted as it is specific to these instructions.

The Node Type Definitions#

You define a new node type using two files, examples of which are in the nodes/ subdirectory. Tailor the definition of your node types for your computations. Start with the OmniGraph User Guide for information on how to configure your own definitions.

Tests#

While completely optional it’s always a good idea to add a few tests for your node to ensure that it works as you intend it and continues to work when you make changes to it. Automated tests will be generated for each of your node type definitions to exercise basic functionality. What you want to write here are more complex tests that use your node types in more complex graphs.

The sample tests in the tests/ subdirectory show you how you can integrate with the Kit testing framework to easily run tests on nodes built from your node type definition.

That’s all there is to creating a simple Python node type! You can now open your app, enable the new extension, and your sample node type will be available to use within OmniGraph.