Robert McGregor schrieb:

> One thing I forgot to mention that I struggled with is differences in display
> gamma, which can really yield a HUGE difference in the *perceived* image output.
> 
> I'm told it affects antialiasing too somehow, but...

It does indeed - somehow. POV-Ray does antialiasing in the same color 
space it uses for rendering, that is linear color space in POV-Ray 3.7 
(unless you use assumed_gamma, which you shouldn't anyway), which has 
the effect that the color difference at which AA kicks in /appears/ much 
higher for dark colors than for bright colors.

Not ideal, but that's how it is at present. Applying output gamma 
adjustment /before/ antialiasing would cause color distortions, depend 
on file type and/or File_Gamma setting, and wouldn't fit in the general 
architecture of 3.7 anyway, so it's no option either.


 > well I must admit that all

> good for compositing" and "Windows is 2.2" and "Mac is 1.6" (or something like
> that). Whatever. I've seen Warp and Clipka going back and forth about it over
> the last few months...

Just let it suffice to say that you really should set Display_Gamma to a 
suitable value as described in the documentation, as from the next beta 
on there really should be no reason left to tamper with the setting.


> Here are three renders of the exact same scene file but with, respectively,
> default gamma (i.e., no command line gamma), Display_Gamma=1.6, and
> Display_Gamma=1.0. I'm not sure why a command line Display_Gamma of 1.0 looks
> *completely* different than the supposed default 1.0 gamma for POV-Ray 3.7
> [i.e., without any Display_Gamma in the command line])?

That's because 1.0 is /not/ the default Display_Gamma; depending on your 
system, it should be 2.2 (PC and Unix), or... well, don't know, maybe 
1.6 for the Mac version.


> I guess I really just

> file images are identical, but this "display" thing really throws me off, since
> all are quite different.

That's because for file output, gamma is now governed by a separate 
File_Gamma keyword.


> This is one area where I can truly appreciate Jaime Vives Piqueres' ignorancia
> mindset... I know what looks good to me, so I adjust according to what I think
> looks right (and if it looks right, it *is* right!)

The thing is that gamma is not an "artistic" screw to tweak, but a 
purely technical one, intended to make sure that what /you/ see is as 
close as possible to what /others/ will see.

If you think your image looks too washed-out, but you are sure that you 
set Display_Gamma to the proper value (not according to what you think 
looks cool, but as explained in the documentation), then what you really 
should do is to fix your scene.

If you try to misuse this technical screw for artistic purposes, don't 
be surprised if the technical side starts getting in your way.


There's currently still one caveat to this principle, and that's input 
image files, which /will/ be rendered too washed-out depending on file 
type. Next beta will do a better job there.


(Readers please note that this all pertains to the current POV-Ray 3.7 
beta; older versions - including the latest "proper" release, 3.6.2 - 
are quite different beasts regarding gamma handling.)

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