Mediums are used to create complex translucent materials. The light will change depending on the characteristics of the surface after entering a "medium". When photons enter the surface they are either scattered or absorbed (actually both). Then they come out of the surface. This process is a very complex process and the Octane Medium is about this phenomenon. Complex materials such as vax, skin, milk and leaf can be produced by this medium. There are 3 different Mediums in Octane: absorption, scattering and volume.
If you want to get realistic and accurate result, you can use Diffuse and Specular materials when using Medium. We also recommend Path Tracing or PMC as Render Kernel. You have to increase the sample count a lot depending on the scene you have. But render times can be a bit long. Unfortunately, the price we will pay for a realistic result is the time unit. We will explain how to optimize your kernel settings at the end of this topic.
Also, make sure your object is closed or thick when using Mediums. In single sided objects, mediums will not work. We also recommend that you keep the Material Reflection low, if the reflection is high enough rays do not enter the object and reflected back. These requirements will be enough that the medium works effectively for the most scenarios.
Finally, the Absorption and Scatter phenomena usually coexist. We have distinguished these 2 things in order to be regular in explaining, but in fact these two should work together for the correct results. Keep this in mind.
ACCESS MEDIUM CHANNEL
Medium channel is available only in Specular and Diffuse Materials. You can use it from one of these.