OctaneRender® supports participating media inside objects. These settings are stored in Octane Medium nodes, which are attached to the corresponding input pin of Diffuse, Specular, and Universal material nodes.


To render with Medium nodes, the Path Tracing or PMC render kernels are the best choices. You can render mediums using the Direct Light kernel, but only if the Medium node is connected to a Diffuse material, and if you set the kernel's Diffuse Mode to GI.

    • Absorption
    • Random Walk
    • Scattering
    • Schlick
    • Standard volume medium
    • Volume gradient
    • Volume medium

Utility

    • Medium switch
    • Phase function switch
    • Volume ramp switch

Figure 1: Octane Medium Node List


There are some things to keep in mind about using Mediums with Meshes and Specular materials:

Meshes

Add Medium nodes to Materials when you've applied them to Meshes that define a closed volume. A single-sided plane will not work. For example, a plane representing a leaf will not work if a Material with a Medium is applied to it. The one exception is a plane representing the ground: OctaneRender treats the ground plane as an infinitely deep surface.

Specular and Null Materials

Specular materials were the best choice when using a Medium node. When using a Specular material, set the value of the Reflection parameter to a low value because only the part of the spectrum that is not reflected can enter the object for scattering. If you set Reflection to 1, all light reflects regardless of the Transmission value. If Reflection is set to 0, all light transmits through the surface, but the result is an unnatural appearance. Reflection values of 0.1 - 0.2 are good starting points.


However, the Null Material node can now be used for mesh objects that have an invisible surface but contain a medium. This is equivalent to setting up a specular material with IOR 1 and a reflection of 0 and a transmission of 1. However, that methodology no longer makes sense with nested dielectric. The Null Material was created to make a medium with no surface work in all cases.