V-Ray supports the rendering of the caustics effects. In order to produce this effect you must have proper caustics generators and caustics receivers in the scene (for more information on how to make an object a caustics generator/receiver read the VRayObjectProperties and Light Attributes documents).
The new Progressive caustics solver uses advanced sampling techniques, and is able to trace as many photons as required without suffering the memory constraints of traditional Photon Mapping techniques.
The other method, New Map (Photon Mapping), is a two-pass technique. The first pass consists of shooting particles (photons) from the light sources in the scene, tracing them as they bounce around the scene, and recording the places where the photons hit the object surfaces. The second pass is the final rendering, when the caustics are calculated by using density estimation techniques on the photon hits stored during the first pass.
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Progressive and From File modes are not available with V-Ray GPU.
New Map (Photon Mapping) works with When the render engine is set to V-Ray GPU , the Caustics rollout is not availableprovided there is a GI calculation in the scene. Some limitations apply.
Multiplier– Controls the strength of the caustics. It is global and applies to all light sources that generate caustics. If you want different multipliers for the different light sources, use local light settings.
Note: This multiplier is cumulative with the multipliers in the local light settings. Changing multipliers, while useful for artistic purposes, will result in physically-inaccurate scenes.
Search distance units – Determines in what units the Search distance parameter is specified - World units or Pixels. The Progressive mode works only with Pixels.
Search distance (World)/(Pixels) – Radius of search area circle.
The Progressive mode works only in Pixels. The value set initially is automatically reduced by the solver during successive passes by up to a fourth of the initial value. For example, with the default value of 4, the search radius after being reduced becomes 1 pixel, allowing for detail to be resolved with that accuracy. If the initial radius is set to 16, the final radius is 4 pixels making the caustics look blurrier. As of V-Ray 5 update 1, it is recommended to leave the radius at its default value of 4.
For the New map mode, when V-Ray needs to render the caustics effect at a given surface point, it searches for a number photons on that surface in the area surrounding the shaded point (search area). The search area is a circle with its center at the original photon and a radius equal to the value. Smaller values produce sharper, but perhaps noisier caustics; larger values produce smoother but blurrier caustics. For more information, see The Search Distance Parameter example or The Light Caustics Subdivs Parameter example below.
Max photons – Maximum number of photons within the search area circle that will be considered when rendering the caustics effect on a surface. Smaller values cause less photons to be used and the caustics will be sharper, but perhaps noisier. Larger values produce smoother but blurrier caustics. The special value of 0 means that V-Ray will use all the photons that it can find inside the search area. See the Max Photon Example below for more information.
Max density – This parameter allows you to limit the resolution (and thus the memory) of the caustics photon map. Whenever V-Ray needs to store a new photon in the caustics photon map, it will first look if there are any other photons within a distance specified by Max density. If there is already a suitable photon in the map, V-Ray will just add the energy of the new photon to the one in the map. Otherwise, V-Ray will store the new photon in the photon map. Using this options allows you to shoot many photons (and thus get smoother results) while keeping the size of the caustics photon map manageable.
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To write and load *.vrpmap files vrpmap files per frame, use %04d %04d frame formatting token.
Caustics also depend on the individual light settings (see Light Attributes).
For accurate caustic calculations, disable the VRayMtl'sAffect Shadows parameter when using caustics. Simultaneous usage of both Caustics and Affect Shadows can be used for artistic purposes but will not produce a physically correct result.
V-Ray GPU supports Caustics rendering within the following limitations:
Texture lights are not supported.
Rendering with V-Ray GPU with RTX is not supported.
VRayBlendMtl is not supported.
Dispersion is not supported.
The supported lights are: VRayLightRect and VRaySun.
