Houdini 21: How to Create a Package

Check out the template here.

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There are a bunch of different ways to create one; what I'm going to show here is the easiest for one individual user. You can check out SideFX's Houdini Package documentation for more detailed information.

1. Navigate to $HOUDINI_USER_PREF_DIR, a Houdini environment variable and create a packages directory if it doesn't already exist.

Windows: C:\Users<your username>\Documents\houdini

MacOS: ~/Library/Preferences/houdini/

2. Create a directory to hold your package in the packages directory. Name it whatever you want your package to be named. I'll use my_package.

3. Create a my_package.json file, named the same as your package directory/package name, and copy/paste the following in, changing my_package to whatever your package is named:

{
  "hpath": "$HOUDINI_USER_PREF_DIR/packages/my_package"
}

When Houdini is starting, it will search $HOUDINI_USER_PREF_DIR/packages for .json files and modify $HOUDINI_PATH as described within them. In this case, all we're doing is letting Houdini know that it needs to look in my_package for stuff, along with its own installation.

4. Add whatever contents you need to your tool. What we'll do in this guide is set up a Python panel that talks to a custom Python library. Inside your package, create two directories: python3.11libs and python_panels. Note that these must match the naming conventions in $HFS/houdini, so HDA's need to go in an otls directory, shelves must go in toolbar, etc.

5. In python3.11libs, create a directory named my_lib. Add an empty __init__.py file and my_script.py, with the following contents:

def hello_world():
    return "Hello, world!"

6. In Houdini, go to Window > Python Panel Editor > New Interface.

   • Save To: wherever your package is / python_panels, ex "/Users/Ben/Library/Preferences/packages/my_package/python_panels/my_panel.pypanel"
   • Name: my_interface
   • Label: My Interface
   • Check "Include in Pane Tab Menu"
   • Check "Create Preceding Separator"
   • Hit Apply
   • Hit Accept
   • Quit Houdini

7. You should now have a .pypanel file that looks something like this (likely your default script is a little different):

<?xml version="1.0" encoding="UTF-8"?>
<pythonPanelDocument>
  <!-- This file contains definitions of Python interfaces and the
 interfaces menu.  It should not be hand-edited when it is being
 used by the application.  Note, that two definitions of the
 same interface or of the interfaces menu are not allowed
 in a single file. -->
  <interface name="my_interface" label="My Interface" icon="MISC_python" showNetworkNavigationBar="false" help_url="">
    <script><![CDATA[########################################################################
########################################################################
# Replace the sample code below with your own to create a
# PySide interface.  Your code must define an
# onCreateInterface() function that returns the root widget of
# your interface.
#
# The 'hutil.PySide' is for internal-use only.
#
# When developing your own Python Panel, import directly from PySide
# instead of from 'hutil.PySide'.
########################################################################

#
# SAMPLE CODE
#
from hutil.PySide import QtWidgets

def onCreateInterface():
    widget = QtWidgets.QLabel('Hello World!')
    return widget

]]></script>
    <includeInPaneTabMenu menu_position="0" create_separator="true"/>
    <includeInToolbarMenu menu_position="201" create_separator="false"/>
    <help><![CDATA[]]></help>
  </interface>
</pythonPanelDocument>

8. Copy/paste this into the script section to replace the current contents, so your new file looks something like this:

from PySide6 import QtWidgets
from my_houdini_lib import my_script

def onCreateInterface():
    # Must return the root QtWidget of your pane.
    widget = QtWidgets.QLabel(my_script.hello_world())
    return widget

---

<?xml version="1.0" encoding="UTF-8"?>
<pythonPanelDocument>
  <!-- This file contains definitions of Python interfaces and the
 interfaces menu.  It should not be hand-edited when it is being
 used by the application.  Note, that two definitions of the
 same interface or of the interfaces menu are not allowed
 in a single file. -->
  <interface name="my_interface" label="My Interface" icon="MISC_python" showNetworkNavigationBar="false" help_url="">
    <script><![CDATA[
from PySide6 import QtWidgets
from my_houdini_lib import my_script

def onCreateInterface():
    # Must return the root QtWidget of your pane.
    widget = QtWidgets.QLabel(my_script.hello_world())
    return widget
]]></script>
    <includeInPaneTabMenu menu_position="0" create_separator="true"/>
    <includeInToolbarMenu menu_position="212" create_separator="false"/>
    <help><![CDATA[]]></help>
  </interface>
</pythonPanelDocument>

9. Open Houdini and in the menu for a new pane, you'll see "My Interface". It displays a label that says "Hello, world!".

Now you can write whatever Python logic you'd like in your library and build a UI to interact with it.