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The basic goal of the photon map is to render true reflective and refractive caustics. The photon map was first introduced by Henrik Wann Jensen (see Suggested Reading).
Photon mapping is a technique which uses a backwards ray-tracing pre-processing step to render refractive and reflective caustics realistically. This means that mirrors can reflect light rays and lenses can focus light. Photons can also interact with media, to show the path the light travels.
A code example:
global_settings {
photons {
count 20000
autostop 0
jitter .4
}
}
light_source {
MyLight
photons {
refraction on
reflection on
}
}
object {
MyObject
photons {
target
refraction on
reflection on
collect off
}
}
Dispersion
Since the refractive index of a material changes as a function of the lights wavelength, light passing through a material will be separated according to wavelength. This is known as chromatic dispersion. It creates a prismatic color effect inside the object.
As POV-Ray does not use wavelengths for rendering, the effect is simulated. Dispersion can also be used in combination with photons (to recreate that famous record sleeve)
Improved RadiosityMany things have changed in radiosity, compared to POV-Ray 3.1. A short overview:
diffuse property of the surface finish.nearest_count to specify the minimum number of old values blended together.
The total number blended will vary depending on error_bound. recursion_limit is not limited to 2. You can specify any
recursion_limit up to 20.adc_bailout for radiosity rays.normal on
to the radiosity block within global_settings.media on to the
radiosity block within global_settings.save_file "file_name" and load the same data
later using load_file "file_name".pretrace_start
and pretrace_end within the radiosity block inside global_settings.radiosity block exists in POV file.max_sample. It takes a float parameter which specifies the brightest that
any gathered sample is allowed to be.Radiosity is still an experimental feature. We cannot guarantee that scenes using these features in this version will render identically in future releases or that full backwards compatibility of language syntax can be maintained.
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