Wednesday, June 25, 2008

VRay Caustics


VRay Caustics

General

VRay 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 information how to make an object a caustics generator/receiver read the Object settings and Lights settings sections in Render parameters > System > Object/Light settings. The settings in this parameter section control the generation of the photon map (an explanation of the photon map can be found in the Terminology section).

Parameters

On - turns caustic on and off.

Multiplier - this 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 then you should use the local light settings. Note: this multiplier is cumulative with the multipliers in the local light settings.

Search dist - when VRay traces a photon that hits an object in some point the raytracer searches for other photons on the same plane in the surrounding area (search area). The search area in fact is a circle with center the original photon and its radius is equal to the Search dist value.

Max photons - when VRay traces a photon that hits an object in some point and counts the photons in the surrounding area it then averages the illumination of that area based on the number of the photons in it. If the photons are more than Max photons VRay will only take the first Max photons of them.

Max density - this parameter allows you to limit the resolution (and this the memory) of the photon map. Whenever VRay 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, VRay will just add the energy of the new photon to the one in the map. Otherwise, VRay 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.

Mode - controls the mode of the irradiance map:

New map - when this option is selected a new photon map will be generated. It will overwrite any previous photon map left over from previous rendering.

Save to file - hit this button if you want to save an already generated photon map in a file.

From file - when you enable this option VRay will not compute the photon map but will load it from a file. Hit the Browse button on the right to specify the file name.

Don't delete - when checked, VRay will keep the photon map in memory after the scene rendering has finished. Otherwise the map will be deleted and the memory it takes will be 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 this is turned on, VRay will automatically save the caustics photon map to the provided file when rendering is complete.

Switch to saved map - this option is only available if Auto save is on. It will cause VRay to automatically set the mode to From file with the file name of the newly saved map.

Notes

Caustics also depend on th

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