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In order to calculate the caustics effects, V-Ray uses a technique known as photon mapping. It 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.

UI Path

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||Renderer tab|| > Caustics tab

(with the V-Ray Renderer node selected)

 

Parameters

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Enable Caustics – Turns the rendering of caustics on and off.

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Max Photons – Specifies the maximum number of photons within the search area circle that are considered when rendering the caustics effect on a surface. Smaller values cause less photons to be used and the caustics are sharper, but perhaps noisier. Larger values produce smoother but blurrier caustics. The special value of 0 means that V-Ray uses all the photons that it can find inside the search area.

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File – File name with the caustics photon map to be loaded when Mode is set to From File.

Don't Delete from Memory – When enabled, V-Ray keeps the photon map in memory after the scene has finished rendering. Otherwise, the map is deleted, so that the memory it takes up is freed. This option can be especially useful if you want to compute the photon map for a particular scene only once and then reuse it for further rendering.

Auto Save – When enabled, V-Ray automatically saves the caustics photon map to the file specified in the Auto save file field when rendering is complete.

Auto Save File – Specifies the file to which the caustics photon map is saved when Auto save is enabled. Click the Browse button to the right to specify the file name.

Show Caclulation PhaseCalculation Phase – When enabled, displays the calculation of the caustics map.

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For this image, the Caustics Subdivs parameter of the V-Ray light is set to 50to 50. This makes the separate photons more distinct. In the V-Ray Renderer Caustics tab, the global caustics Multiplier is 1is 1, and Max Photons is set to 0to 0. As seen from the images, the larger Search Distance produces blurrier caustics.

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This example is similar to the previous one, but the Caustics Subdivs parameter for the V-Ray Light is increased to 300to 300. The other Caustics parameters in the V-Ray Renderer are the same as in the previous example. As can be seen in the images, the larger number of photons produces smoother caustics effects than in the previous example. 

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