As a renderer I used Arnold and was pretty satisfied with the workflow. However I was wondering how difficult would it be to use the same OSL shaders in another renderer, e.g. Blender’s Cycles. Especially because I was trying to mimick OpenCL’s syntax in OSL (not the best idea, but helped me port OpenCL shaders which I built first), included couple of header files etc..
As it turned out it was a pretty quick process and everything worked out of the box, requiring only minimal changes. The only thing I had to change was to properly set up multiple node outputs. Arnold doesn’t support multiple outputs for an OSL node so I worked around it by outputting a 4×4 matrix type with encoded values in it and extracting them afterwards. This makes Blender’s shaders nicer and more readable, you can check the diff here.
The shading setup in Blender looks pretty similar to the one used in Arnold and also outputs similar results.
For the testing I used Blender 2.80 beta running in a Docker container.
Keep in mind that rendering such volumes is pretty slow and neither Arnold nor Cycles support OSL on GPU. I included the changes in blender branch of the repository (not for all OSL shaders yet, but you get the idea :)).