NVil-Houdini AppLink

This program automates geometry interchange between NVil (Homepage/Steam) and Houdini.

How does it work?

Let’s say you’re modeling an object in Houdini, but soon realize that some things would be faster to complete when done with NVil - a dedicated modeling program.

With NVil open in the background you can select a SOP that you want to edit and click on export button on a toolbar that is included with this AppLink. Your geometry will be immediately exported to NVil via Houdini’s internal OBJ exporter and saved to NVil %APPDATA%\DigitalFossils\NVil\Media\Clipboard\ClipboardObj.obj file.

After you’re done modeling in NVil, you can select objects which you want to export, and execute Export to Houdini composite tool (also included).

On Windows, import process in Houdini is automated via Python RPC module (rpyc~/~hrpyc). On GNU/Linux, you need to manually execute Import shelf tool.

Requirements

Possible setups

The AppLink works and has been tested on the following configurations:

• (Deprecated) NVil and Houdini installed on MS Windows 7. I didn’t test it on later Windows versions and I also will have no plans of supporting this system simply because I no longer have access to a machine running it. Forks and pull requests are welcome.
• NVil installed in WINEPREFIX (GNU/Linux).

Common

Python

Python 2.7.x and pip.

Windows

Python RPC Module

Used for communication with Houdini hrpyc server.

pip install rpyc

Network ports

When running both programs on Windows, port 18811 must be open for communication as this the default port used by hrpyc.

GNU/Linux

Wine

Necessary to run NVil.

Installation

Start by cloning the repo into your $HOUDINI_USER_PREF_DIR. On Windows it’s usually your Documents\houdini_something directory. On GNU/Linux it’s whatever you tell it to be. You can also download the repo manually and unpack it that location.

houdini.env

You need to put the following global variables in your houdini.env file (or define them system-wide):

NVIL_APPLINK_DIR=
WIN_APPDATA=

NVIL_APPLINK_DIR currently it’s only used by the shelf to tell it where the icons are located. WIN_APPDATA is the path to your Windows user’s %APPDATA%, usually found in C:\Users\username\Application Data.

Windows example:

NVIL_APPLINK_DIR="c:\Users\YourUser\Documents\Houdini 17.5"
WIN_APPDATA="c:\Users\YourUser\Application Data"

Theoretically, you could try using %HOME%\Documents\Houdini 17.5 in NVIL_APPLINK_DIR, and %APPDATA% in WIN_APPDATA, but I cannot test it anymore so I can just speculate on whether it would work or not.

GNU/Linux example:

NVIL_APPLINK_DIR="$HOUDINI_USER_PREF_DIR/nvil-houdini-applink"
WIN_APPDATA="$HOME/wineprefix/drive_c/users/youruser/Application Data"

Additional steps for Windows

Open NVil and choose Composite Tools->Import Composite Tools. Point at composite_tools/export-to-houdini.xml in the repo to install it.

Dive into Edit->Customize->Composite Tools, select Export to Houdini tool and then Common Shortcut Tools >> Launch App(*) from Set 1.

In Param input string, modify Path(string) parameter to point at your Python 2.7.x executable, for example: c:\Python27\python.exe. Arguments(path) should by default be okay and set to nvil_houdini_applink.py. This tells NVil to launch the module after Clipboard Copy (obj) command, which will point Python to nvil_houdini_applink.export_from_nvil().

How to use the AppLink?

In both setups, make sure that both: NVil and Houdini have been started. ;)

Windows/Windows

Start hrpyc server by clicking the RPC button located on NVil AppLink shelf, or just type:

import hrpyc
hrpyc.start_server()

in the Houdini’s Python shell. This will get RPC server up and running and listening on default port 18811.

To export your model to NVil, select a SOP containing polygonal geometry and hit Export shelf tool. This saves your geo to $WIN_APPDATA/DigitalFossils/Media/Clipboard/ClipboardObj.obj and instructs NVil to load the file. You will be taken to NVil’s window with import/export options modal window open. After clicking OK, NVil will load the model.

When you’re done editing it, select what you want to export and then launch Export to Houdini composite tool. You will once again be presented with import/export modal window and after clicking OK, the model will be passed to Houdini.

See Importing from NVil for further steps.

Importing from NVil

Importing from NVil happens automatically on Windows/Windows setup. If you’re using Wine/GNU+Linux setup, it requires pressing the Import button.

Import will either succeed or fail, depending on where you were in Houdini network at the moment of importing the modified geometry, and which node you had selected at that moment.

There are two rules guaranteeing successful import:

1. You need to be inside an ObjNode, like geo SOP.
2. You need to have either nothing, or a SopNode selected.

By selecting nothing, a loose and frozen file operator linking to $WIN_APPDATA/DigitalFossils/Media/Clipboard/ClipboardObj.obj will be created in the current network path.

By selecting a SOP node, the same frozen file SOP will be created, but it will become a child of the selected node.

And that’s it.