clipka <ano### [at] anonymousorg> wrote:
> Am 22.12.2016 um 05:08 schrieb Dave Blandston:
> > clipka <ano### [at] anonymousorg> wrote:
> >> The second image shows essentially the same scene with `assumed_gamma
> >> 2.2`, with the diffuse settings (`diffuse` and `brilliance`) adjusted to
> >> get exactly the same diffuse effect out of the different colour math.
> >
> > Please forgive my ignorance, but does that mean the default settings for diffuse
> > and brilliance are meant to give the most visually appealing results with an
> > assumed_gamma of 2.2?
>
> It is more complicated than that.
>
> > I never really gave assumed_gamma much thought. I just noticed that setting it
> > to 1.0 produced a washed-out result so I picked 2.2 and never thought about it
> > again.
>
> Here are a few facts:
>
> - The brilliance default of 1 fits /perfectly/ with `assumed_gamma 1.0`,
> because the developers back then naively implemented a formula that was
> designed for linear colours. The whole `brilliance` mechanism is an
> awfully hackish thing, and it so happens that it can be used to achieve
> the same proper look with other gamma settings (as far as diffuse goes),
> so my guess is that it was introduced specifically for the purpose of
> fixing the look of diffuse objects, in times when people probably didn't
> even know what gamma handling was.
>
> - The diffuse default of 0.7 was presumably introduced in times when bad
> gamma handling was the norm, and it can be assumed that it was set in
> such a way as to get pleasing results in /that/ environment. In a gamma
> 1.0 scenario, that would correspond to a setting of about 0.45.
>
>
> - As Warp demonstrated not long ago, one main reason (besides trying to
> use gamma-pre-corrected colours without the "srgb" keyword) for the
> washed-out look in gamma 1.0 mode seems to be the "ambient" default:
> That setting, too, was quite certainly designed for a gamma of about
> 2.2, and in a gamma 1.0 scenario that would correspond to an ambient
> setting of 0.006 (though that number is difficult to nail down, as
> ambient is always added to colours, and adding colours without proper
> gamma handling greatly distorts them, particularly if their absolute
> value is rather small.)
>
>
> - Without proper gamma handling, there is stuff that you just simply
> /cannot/ get right simultaneously (as demontrated with these images); so
> you may need a /lot/ of tweaking to get /somewhat/ close to a realistic
> look, and you'll have to do this /over and over again/ for virtually
> each and every scene, as you'll need to fine-tune yor materials for the
> given lighting conditions and vice versa. On the other hand, with gamma
> 1.0 all it takes is some experience, and once you get your materials
> right you can re-use them quite easily in virtually every lighting
> condition. (Also, with proper gamma handling the number of knobs to
> tweak is smaller, since you never need to fiddle with any of those
> unrealistic hacks like brilliance, reflection exponent, or light source
> fade_power values other than 2.0.)

Interesting. Do the default values now reflect assumed gamma 1.0 then or do we
still have to tweak them for assumed gamma 1.0?

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