I have an issue every time I try to render volumes with Octane, the same issue with both Octane 4 latest build and 2018.1.
When I interactively change some of the settings on the volume shader, the IPR updates to what looks to be the correct changes that I would expect, but then when I refresh the IPR it changes back to a much higher density. It also renders the much darker/denser volume. The step length seems to have the biggest affect on it, but I'm finding it incredibly difficult to get any reliable sense of how it will come out by changing the parameters without being able to see interactively how it will look once refreshed.
I hope this makes sense and I've attached images to try and illustrate the issue. Since nobody else has posted about this on the forums, I imagine it must just be something I'm doing, but I have tried at different points with different scenes in the last couple of months to get it working, without any luck. I'm also attaching a test scene, in case there's anything obvious in there that I'm doing wrong.
If you are able to take a look, that would be amazing!