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On 03/15/2018 06:01 PM, Norbert Kern wrote:
> William F Pokorny <ano### [at] anonymous org> wrote:
...
>>
>> I got a couple small renders done yesterday - with and without the
>> emission - and compared them. At a high level adding in emission the
>> color of the background sky makes the clouds look as if they are sitting
>> in a hazy atmosphere without having modeled the hazy atmosphere. See the
>> attached image.
>>
>> The difference image on the right shows an aspect or pitfall of the
>> method - depending on one's goal I suppose. Once one or more color
>> channels for the media 'interval' being sampled is maxed out (Red here),
>> you get a 'disjoint' color-hue change in the media due the emission
>> adder.
>>
...
>
> Interesting. I wouldn't have thought the effect of small emission value is that
> strong. I've to do more tests...
>
> Norbert
>
>
Sorry slow - busy with real life.
Emission is stronger by nature because the emission intensity increases
with depth of media. If you want to 'sort of' match a scattering
intensity with an emission media, you have to add absorption at about
the same value as the emissive value (1).
I've always used scattering+absorption, emission+absorption or
emission+scattering. Never all three - intentionally at least - as
Gilles did here (2).
Bill P.
(1) - An idea on my to play with list is some method to pre-render or
pre-calculate scattering with attenuation media so as to be able to
create a faster emission+absorption or a scattering without attenuation
+ absorption media model for use in follow-on renders.
(2) - I've wondered some recently about whether POV-Ray should support
two absorption specifications given Gilles technique looks useful.
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