OctaneRender supports participating media inside objects (AbsorptionDefines how fast light is absorbed while passing through a medium., Subsurface ScatteringDefines how fast light gets scattered when traveling through the medium., and Volume). These settings are stored in Medium nodes, which are attached to the corresponding medium inputs on material nodes.
Medium nodes can be accessed from Create Nodes > New Medium
NOTE: MediumsThe behavior of light inside a surface volume described by scatter, absorption, and transmission characteristics. will only work correctly on Meshes that have thickness (a closed volume). A single-sided plane will not produce correct results. e.g. A plane representing a leaf will not work correctly if a MaterialThe representation of the surface or volume properties of an object. with a Medium is applied to it.