The release archive contains everything you need to run HtoA, including the Arnold libraries, executables and Python modules.

Compatible Houdini Products

  • The HtoA build must match exactly your Houdini install, down to the build number, or random crashes and glitches will occur.
  • HtoA requires a 64-bit Houdini, Houdini FX or Houdini Education.

Houdini Apprentice unfortunately cannot run HtoA as they lack support for third party renderers, see Houdini products comparison.

Using the Graphical Installer

Here are step by step instructions to install HtoA for the current user.

  • Download the installer matching your exact Houdini version and platform from Solid Angle Downloads.
  • Launch the installer:


  • Select the folder where you want the HtoA files to be extracted:


  • You can choose to either have the installer set up your Houdini config file for HtoA automatically for you, or just extract the contents to do a manual installation. The automatic installation will modify a few lines in your houdini.env file and create a backup.
  • You need to accept the End User License Agreement to continue the installation:


  • You are now ready to install HtoA on your computer:


  • The actual installation is then performed:


  • Done! You can now launch Houdini and start using Arnold:


Manual Installation

If you need to have complete control of the HtoA installation, can you select to only extract the contents off the installer and configure Houdini to pick up HtoA as shown below.

Modifying the HOUDINI_PATH

The installation boils down to inserting the HtoA folder first in the HOUDINI_PATH environment variable. On Windows, you also need to update the PATH environment variable. 

The path to the HtoA folder must be inserted before the factory Houdini folders in the HOUDINI_PATH. We suggest you put it first.

The instructions below were written for Houdini 13.0.509 and HtoA 1.0.0, please replace the versions numbers where appropriate.

In case you are also setting one of the following environment variables, make sure you are appending ";@;&", at the end of its value, or alternatively add the corresponding HtoA sub-folder path to it:

Environment variableSub-folderNotes
HOUDINI_DSO_PATH <htoa_folder>/dso 
HOUDINI_SOHO_PATH<htoa_folder>/sohoIt is critical that the HtoA soho sub-folder be placed before the factory Houdini folder.

Simple installation with houdini.env

The simplest installation is to insert the HtoA folder path to the houdini.env file. This file is created by Houdini after your first run, its location varies per platform:

WindowsC:\Documents and Settings\<username>\My Documents\houdini13.0\houdini.env

On Linux and Mac, append a single line to enable HtoA for the user: 

houdini.env (Linux)
houdini.env (Mac)


On Windows, you need to set the PATH to point to the scripts/bin as well:

houdini.env (Windows)
  • Prior to Houdini 15.5.559, must use forward slashes ("/") on Windows instead of backslashes as path separators. For example: "C:/solidangle/htoadeploy/12".
  • In the PATH, the HtoA binaries folder must be appended (not prepended) to avoid issues with the Houdini Engine plugin in other applications.


Using a wrapper script

The most flexible way to deploy HtoA is to use a wrapper to launch Houdini. On Linux for example, you could use this script:

Further information


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