The Random Walk node is a newer variant of subsurface scattering that utilizes a stochastic or random process for the scattering of light through an object. This provides the most realistic result when rendering scatter volumes. The Random Walk parameters are similar to the Scattering node's parameters with a few exceptions (Figure 1).

Figure 1: Random walk Node

Parameters

    • Compatibility version - The Octane version that the behavior of this node should match.
    • Density - Determines the density of the particles in the surface. The larger the scale value, the more likely light will be absorbed when passing through the surface.
    • Volume Step Length - Depending on the surface, you may need to adjust this parameter. The default value is 4, but if the volume is smaller than this, you need to decrease the value. Decreasing this value decreases render speed, and increasing the value causes the ray marching algorithm to take longer steps. If Volume Step Length exceeds the volume's dimensions, then the ray marching algorithm takes a single step through the whole volume. To get the most accurate results, keep Volume Step Length as small as possible.
    • Volume Shadow Ray Step Length - The step length that is used by the shadow ray for marching through volumes.
    • Use Volume Step Length for Volume Shadow Ray Step Length - If active, uses Volume Step Length as Volume Shadow Ray Step as well.
    • Single scatter amount - Determines how often we calculate direct light in volumes, as a ratio of scatter events.
    • Sample Position Displacement - Allows a texture to control a volume's sample position displacement.
    • Volume padding - Expands the volume bounding box by the given percentage in all 6 directions, but only if sample position displacement is being used.
    • Albedo - Determines the color that is being scattered.
    • Radius - Determines the depth that the light scatters in the medium where black provides no scattering and white fully scatters.
    • Bias - The bias of the subsurface scattering. Higher values use biased sampling, which usually yields better results with lower depth settings. Visually, lower values will bias towards the Radius color and higher values will bias towards the Albedo color.