Deborah R. Fowler
Command Line Rendering in Houdini with Karma
Posted on Aug 21 2018Updated June 4 2025 and Oct 4 2024 video
Updated Feb 13 2026 to add animated script
USD Table of Contents
also on https://youtu.be/jmOyAcHTFC0
Example commands (use in the houdini command tools "terminal" window or on linux, a terminal - both should have the houdini env installed)
Single Frame
If you want to use husk to test a frame you can also make it lower res on command line with the -r flag
husk -f 1 -r 320 180 nameOfYourFile.usd
NOTE: when rendering command line, if there does not exist a render folder type either make one, or use the flag below (Rendering from gui will automatically create the folder)
mkdir folderName
You can also add the flag to your command line for example (note for linux, add ticks to '$F4')
husk --make-output-path -o render/test.$F4.exr --engine xpu -f 1 -n 100 -r 320 180 kermit.usd
- --make-output-path will force it to create the folder (directory) if it does not exist
- -o redirects the output, in this case to the render
folder and labels them test.0001.exr, test.0002.exr etc
- --engine xpu specifics the engine you want to use, options cpu or xpu
- -f start frame
- -n how many frames - leave this off and you will get a
single frame (see note below about troubleshooting
sequences)
- -r 320 180 is the frame resolution
In Windows
Easiest way to get a terminal window with the Houdini environment set up is to use the Houdini Launcher and under Launch select Command Line Tools
(This is just a shortcut to the hcmd command in the Houdini bin)
The method we will use differs from the one used for Redshift and Mantra. We were able to use the hipnc directly. Now with command line you will be using a usd file. For those of you familiar with other rendering engines, this would be similar to Renderman: prman file.rib or Arnold: kick file.ass or for that matter if we had written ifd files with Mantra. One of the reasons for moving to Karma was to use USD file format and introduce the USD environment.
USD - no, not US dollar, but "Universal Scene Description" developed by Pixar. For more on USD see my section on Houdini and USD
USD is a toolset for reading, writing, editing and previewing 3D data. It is "stackable" in non-destructive layers (think Photoshop).
Hydra is an API for generating an image from a USD scene. USD consists of C++ libraries with Python bindings for scripting.
Using karma in a lop network (either solaris or in sop/lopnet1) tab and select karma. You will see the karma rendersettingsnode and a usdrender_rop1. The usdrender_rop will render from gui. What you need is a usd_rop to write your usd file. In addition, your geo must be written out to avoid specific path references.
Example files here (these files have been tested on the renderfarm as well for 19.5.640 - once the image is in place and the version of 20 is determined those will be tested as well. Both versions have been tested locally on my desktop).
- command line rendering works on your usd scene file. With the above example file do the following:
- run Command Line Tools and cd to the directory where your
usd file is located
- husk scene.usd (in Houdini Indie, if on apprentice it will tag it with usdnc)
- (husk or husk.exe -f 3 scene.usd would render frame 3 for
example, type husk to see all flags)
- this command will produce your render in exr format - in the
example file I have set it to not go to a folder since karma
will not automatically create a render folder
In the example files I also included a usda file to look at to
aid understanding.
- if you are using a usd file (will not work on usdnc files) you can examine the ascii version of your file by converting it using
- usdcat file.usd --out file.usda
- usdcat -o file.usda file.usd
In Linux
In linux, the instructions are the same, however the regular
terminal window is already ready for you.
Troubleshooting Sequence renders
I recommend testing your usd files before sending to the farm with a single frame render. If you wanted to render a sequence locally you can but beward that the behavior of animated time samples may not be as you might expect. A quick local workaround is to run the following script to force single frame renders.
testfile here
Copy this python file into your folder( replace the name with your scene file) and from the command line type:
python huskAsSingleFrames.py
If using an animated texture or light you may need to change your usd (see animated texture) or if single frames are working you can use subprocess to run husk as single frames.
There is a longer explanation of usd from command line from Gridmarkets:
https://support.gridmarkets.com/portal/en/kb/articles/houdini-lops-submitter-properly-exporting-usd-files-rendering-caches-pipeline-v2#:~:text=Houdini%20is%20never%20opened%20on,need%20to%20do%20when%20submitting.