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 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).
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.
![[Caustics parameters]](vray_for_3ds_max_manual/caustics/caustics.png)
On
- turns rendering of caustics 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 distance - 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 in fact is a circle with center the original
photon and its radius is equal to the Search
distance value. Smaller values produce sharper, but perhaps more
noisy caustics; larger values produce smoother, but blurrier caustics.
Max photons - this is the maximum
number of photons 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.
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.
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
V-Ray 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.
File - the file name with the caustics
photon map to be loaded when the Mode is set
to From file.
Don't delete - when checked, V-Ray 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, V-Ray
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
V-Ray to automatically set the Mode to
From file with the file name of the newly saved
map.
