This page provides information about the Volumetric Overrides rollout of the Render Settings Overrides tab.
Overview
The Volumetrics Overrives allow you to enable probabilistic sampling for volumetrics.
UI Path: ||Render Settings|| > V-Ray > Overrides tab > Volumetrics rollout
Parameters
Enable Probabilistic Volumetrics – When Probabilistic Volumetrics is enabled, the volumetrics select only a few samples (based on the smoke density) along each camera ray. Then, evaluate the volume lighting at those points. When disabled, the volumetrics evaluate the lighting at regular intervals using many steps along each camera ray, and thus each pixel takes longer to render. However, when it's finished, it has no noise at all. Enabling Probabilistic Volumetrics is particularly useful when using the Progressive Image Sampler in V-Ray, as well as when using complex lighting on the volume. The Probabilistic Volumetrics option makes the shading much faster, but also it can result in noisier renders with low sample counts. This mode applies to the Volumetric Grid (VRayVolumeGrid) only. When using the V-Ray GPU renderer, this option is not available in the UI, but is automatically turned on and the are set to 1.
Number of Direct Samples – Specifies the number of probabilistic samples to use when Probabilistic Volumetrics is enabled. For the best render performance, use a higher number of samples for transparent smoke, and a lower number for dense smoke. A very high number of samples will converge to standard ray-marching.
Number of GI Samples – Specifies the number of probabilistic samples to use for GI rays when Probabilistic Volumetrics is enabled. This should be kept at a relatively small number in order to speed up GI calculations.
