POV-Ray : Newsgroups : povray.bugreports : Ambient Hates Radiosity : Re: Ambient Hates Radiosity Server Time
30 May 2023 10:21:53 EDT (-0400)
  Re: Ambient Hates Radiosity  
From: clipka
Date: 6 Dec 2015 05:57:04
Message: <56641480@news.povray.org>
Am 06.12.2015 um 09:38 schrieb Sven Littkowski:
> Not sure if this error was fixed with the latest updates: using
> radiosity, ambient 1.0 does not function, it is like a regular color (no
> ambient glow).

This breaking change is entirely intentional, and is related to the
"ambient" mechanism having previously been used for two entirely
different things:

(1) To model light a surface emits in and of itself, making the object
appear to glow; that's what you're attempting to do.

(2) To model illumination an object receives from other nearby objects
(aka "ambient illumination"), brightening shadows that would otherwise
appear pitch black; that's what the mechanism was originally designed to to.

Now in classic non-radiosity scenes these uses can happily coexist, and
everything is fine there.

In radiosity scenes however, (2) is covered by the radiosity mechanism
itself, so in this respect the ambient mechanism needs to be disabled.
This can be done by setting all textures to "ambient 0", but this
precludes using the same texture definitions for both radiosity and
non-radiosity scenes; or it can be done by setting "ambient_light 0" in
the global settings, but this precludes the use of the ambient mechanism
for (1).

During development of 3.7, it was therefore decided to provide an
entirely separate mechanism dedicated to (1), which uses the keyword
"emission" instead of "ambient". The new mechanism works almost exactly
the same as the "ambient" mechanism used to, except that there is no
global "emission_light" setting.

To make people aware of the new emission mechanism, and to more or less
gently nudge them towards using it when they want to model glowing
materials, it was also decided to go the whole length and entirely
disable the ambient mechanism in radiosity scenes (unless the scene is
identified as a pre-3.7 legacy scene).

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