Arion is described as 'is the hybrid-accelerated and physically-based light simulator developed by RandomControl. It inherits all our expertise in light simulation and makes it run on steroids, thanks to our very unique approach to massive CPU+GPU+LAN computation' and is an app in the System & Hardware category. There are more than 25 alternatives to Arion for a variety of platforms, including Windows, Mac, Linux, Autodesk 3ds Max and Sketchup. The best alternative is Adobe Dimension. It's not free, so if you're looking for a free alternative, you could try LuxCoreRender or POV-Ray. Other great apps like Arion are Keyshot (Paid), V-Ray (Paid), appleseed (Free, Open Source) and RenderMan (Free Personal).
fryrender is the physically-based light simulator developed by RandomControl. It is a photo-realistic render engine where all the elements involved in the generation of the final image (materials, lights and cameras) are based on physically accurate models.