UI Path for V-Ray 5 and earlier V-Ray versions: ||Environment and Effects window|| > Environment tab > Atmosphere rollout > Effects > PhoenixFD
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UI Path for V-Ray 6: ||Render Setup window|| > V-Ray tab > Global switches rollout > Advanced > Probabilistic volumetrics
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Atmosphere settings
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Gamma Correction | gamma_mult – – A multiplier for the gamma of all Phoenix objects in the scene.
Export and render in V-Ray GPU as VRayVolumeGrid | atmosexportasvolgrid – (V-Ray only) This option forces the Phoenix simulators to convert to VRayVolumeGrid objects when rendering in V-Ray RT or when they are exported to a .vrscene file, which enables them to render on machines that do not have a Phoenix license. Note that an exported Volume Grid will correspond to the features available in the respective V-Ray version that will be used to render it.
Use Probabilistic Shading | prob_rend – This option is available only with Phoenix for V-Ray 5 and older earlier V-Ray versions. Since V-Ray 6, this option is in the called Probabilistic volumetrics and is located in Render Setup window →V-Ray settingstab → Global switches rollout. This mode works only for Simulators in Volumetric render Mode and Particle Shaders which have their Render as Geometry option disabled. This option can speed up rendering of fire/smoke or particles, but could also slow it down in some setups, so you have to experiment with the Samples and GI Samples optionsthe Samples and GI Samples options. When Use Probabilistic Shading is enabled, the volumetrics will select a only few samples (based on the smoke density) along each camera ray, and evaluate the volume lighting at those points. When disabled, the volumetrics will evaluate the lighting at regular intervals using many steps along each camera ray, and thus each pixel will take longer to render, but when it's finished, it will have no noise at all. Enabling Use Probabilistic Shading is particularly useful when using the Progressive Image Sampler in V-Ray, as well as when using complex lighting on the volume. Please read through the Volumetric Rendering In-Depth section for examples on setting up fire/smoke and particle rendering for the best performance. When using V-Ray GPU, this option is not available in the UI, but is turned on and the Samples and GI Samples are set to 1.
Samples | prob_samples – Specifies the number of probabilistic samples to use when Use Probabilistic Shading is enabled. For the best rendering performance, use a higher number of samples for transparent smoke, and lower number for dense smoke. A very high number of samples will converge to standard ray-marching.
GI Samples | prob_samples_gi – Specifies the number of probabilistic samples to use for GI rays. The number of samples depends on whether the volumetric has an emissive component. Brighter emission requires more samples, while pure smoke can work with fewer.
