POV-Ray : Newsgroups : povray.documentation.inbuilt : Emission : Re: Emission Server Time
8 Dec 2023 06:45:44 EST (-0500)
  Re: Emission  
From: clipka
Date: 21 Nov 2016 13:37:44
Message: <58333ef8$1@news.povray.org>
Am 21.11.2016 um 18:19 schrieb Jim Holsenback:
> On 11/21/2016 10:16 AM, Mike Horvath wrote:
>> I don't think this is the primary reason to use emission. I think that
>> emission is supposed to be used for glowing objects. The wording makes
>> it seem like it is just a hack to retain old behavior from POV 3.6. This
>> is what threw the developer off in the thread I linked to.
> to quote myself from an earlier post in different NG ... mo betta?
> http://wiki.povray.org/content/Reference:Finish#Emission

Actually, no -- sorry ;)

"There has been a Change as of version 3.7 that allows you to add the
emission keyword to the finish block. One intention is to simplify the
use of materials designed for non-radiosity scenes that are in scenes
with radiosity, or the design of scenes that can be rendered with or
without radiosity. However, emission can also be used with objects that
are intended to glow."

That description implies that there would be two entirely different use
cases: one radiosity-related, and one related to glowing materials. The
truth is that they are one and the same.

Maybe something like this:

The `emission` keyword, NEW in version 3.7, can be used to model glowing
materials, eliminating the need to co-opt `ambient` for this purpose.

The syntax and effect are virtually identical to `ambient`, except that
`emission` is unaffected by the global `ambient_light` parameter, and is
not turned off when using radiosity.

Also, the "Ambient" section may need a bit of love and care as well; I
suggest replacing the last paragraph before the final note with
something like this:

Ambient light affects both shadowed and non-shadowed areas, so if you
turn up the ambient value, you may want to turn down the diffuse and
reflection values.

There has been a CHANGE as of version 3.7 in that the `ambient`
mechanism is now automatically turned off when radiosity is enabled
(provided `#version` is set to 3.7 or higher), allowing you to use the
same material definitions for both radiosity and non-radiosity scenes.
As a consequence, the practice of co-opting `ambient` to model glowing
materials will no longer work in radiosity scenes and is therefore
strongly discouraged altogether; instead, the new `emission` keyword has
been added specifically for this purpose.

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