Environment Variables

You can use the hconfig command line utility to display all Houdini environment variables. Here are those relevant to HtoA, set them in houdini.env or in a wrapper script:


This documentation you are reading is linked in the HtoA components inside Houdini, so that when you click the Help button or press F1, the appropriate page shows in your browser.

However, the default Houdini help browser does not support the HTTPS secure protocol necessary to access the Solid Angle support and documentation server. Let's define the command to open the default browser on the system to open the help URLs:



Setting this environment variable will print any error related to loading the HtoA plugin on the command line, which is very useful to diagnose installation issues:


These environment variables are useful to the HtoA developer and enable more verbose console output and additional features in Houdini. Please refer to the Houdini documentation for details.


If you are getting errors such as these:

Then you might be using the wrong Python version, probably one installed on your system when HtoA needs Python 2.6. You can fix this by forcing the use of Houdini's built-in version of Python:


If this environment variable exists and is set to 0, the startup log listing the Arnold shaders that were loaded will be silenced:


In interactive and batch modes, HtoA needs to export the scene as a temporary .ass file. This temporary file is deleted after reading. You can control the temporary .ass file location and timeout with the HTOA_TMP and HTOA_TMP_TIMEOUT environment variables. The timeout is specified in minutes.


The number of maketx processes to execute in parallel when the number of workers passed to htoa.material.updateAllTx() or set on the Arnold ROP is 0. If this environment variable is not set, the default number of workers is the number of logical cores, clamped to a maximum of 10.

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