The Persistence of Vision Raytracer (POV-Ray).

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Attached to Project: POV-Ray
Opened by Christian Froeschlin - 2010-05-30
Last edited by William F Pokorny - 2017-01-19

FS#118 - More efficient handling of fading lights

Currently, fading light sources are used for lighting and shadow
calculations even when so far away as to no longer have any effect
on the outcome. The proposed solution is to add a new keyword
fade_cutoff_distance which tells povray to ignore the light
source when alluminating a point at larger distance.

A sample implementation is provided in the attached files. These
changes are still based on beta 34 as sources for the current beta
are not yet available, and starting to merge changes to beta 35
only at this time didn’t seem worth the effort. Also, please
disregard, changes in the CVS header comments (I also use
CVS locally for managing source files).

Further considerations regarding this feature:

- For special effects this feature can also be used if the light
source does not actually use fading. On the other hand, cutting
the light at some distances can be considered an extreme form
of fading which may justify the keyword name anyhow.

- Depending on how  FS#46  is implemented, the test for cutoff may
then be needed at another location as well.

- The default value currently is 0 (or *no* cutoff distance). For
#version 3.7 of higher, the default could be chosen automatically
based on the light source intensity and adc_bailout, although it
may then need to be overriden by the user for extreme pigments.

Christian Froeschlin commented on Sunday, 06 June 2010, 13:19 GMT

Argh .. just noticed that the files in the first zip file
accidentally contained other changes not related to this patch,
so here is an updated version.

I need to find a better way to manage povray sources here.

Thorsten Fröhlich commented on Tuesday, 23 August 2011, 06:05 GMT

I think this could be added after 3.7 release assuming this code is licensed until GPL/AGPL. Then Chris Cason could merge it, I suppose.

Christian Froeschlin commented on Tuesday, 23 August 2011, 22:15 GMT

The changes are mine, feel free to use them under any license desired.

William F Pokorny commented on Thursday, 19 January 2017, 15:34 GMT

Now tracked on github as issue #195.


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