"Bald Eagle" <cre### [at] netscapenet> wrote:
>
> I'm almost over here crying with laughter, because I can just hear my girlfriend
> now:
> "And this....   ***THIS*** is what you do ..... for "fun" ???!"
>
Ha! I know the feeling; *everything* takes a back seat when I'm hunkerd down
with POV-ray. As I keep explaining to friends, it's the only way to *learn*!
>

> The new tone-adjusting formulas are:
>
> #declare SRGB_Encode = function (C, M) {
>  select (C-0.0031308, C*12.92*M, C*12.92*M, (1.055 * pow (C, 1/2.4) - 0.055)*M)
> }
>
> #declare SRGB_Decode = function (C, M) {
>  select (C-0.040449936, C/12.92, pow ((C+0.055)/1.055, 2.4)*M)
> }
>
> using M as a multiplier.  Looks like it works correctly, even with  M > 1.
> Perhaps it's not "right", but it's the way I envisioned its usage.
>
That's...brilliant. As are your graphing results. Congrats on the hard work!

I've been re-reading that NVIDIA article that I mentioned; it has some really
astute observations to make. I'm paraphrasing quite a lot here, to try and make
it applicable to POV-ray; and I borrowed another illustration from there (posted
below):

"If the linear lighting values as seen in POV-ray's assumed_gamma 1.0
environment are properly encoded for the saved file, when you view the final
image file it should again look like a real object with those reflective
properties." In other words, by using the true RGB to SRGB conversion formula to
'encode'  the file to preliminarily 'brighten' the image even more, before
sending it to the 'reverse' 2.2-gamma monitor, the end result will be linear
lighting again. Absolute realism (but only as good as it can be, of course, when
perceived on a typical non-HDR monitor.)
As in Image A, with its sharp shadow-terminator line.

"But if you were to display the assumed_gamma 1.0 image file on a gamma 2.2
monitor *without* pre-encoding the file with the formula,  the image will
actually look darker." Or rather, with incorrect gamma interpretation.
As in Image B.
(And as *I* used to do in a different way in v3.6xx days-- using 'plain' RGB
colors and assumed_gamma 2.2; essentially the same result.)

"With more 'advanced' lighting techniques that you use (such as HDR, global
illumination of any kind, and subsurface scattering), the more critical it will
become to stick to a linear color space to match the linear calculations of your
sophisticated lighting."

Apparently, Image A *is* how we see things in the real world, with our eyes.
Which is of course combined with real-world 'radiosity' and fill light, so we
probably don't perceive things *exactly* that way, but close to it. Whereas,
Image B is what many of us *think* we should see-- probably based on how photos
and films of the real world look, at least with older film technology. I think
that was part of Warp's fundamental argument with Clipka, back in 2010 (and my
own argument then too.)

But digressing a bit, and getting back to fundamentals:
It seems to me that there are two 'schools of thought' when rendering in
POV-ray: the *absolute lighting realism* of the assumed_gamma 1.0 way-- Image
A-- and the 'photographically pleasing or expected' look of the assumed_gamma
2.2 (or gamma srgb) way, Image B...even with its 'incorrect' lighting
computations and gamma. (Incorrect as to absolute realism.) Such images
generally have higher contrast and richer colors. Did old photos and films
reproduce absolute 'linear light' realism? No. But they looked nice anyway. ;-)
I wouldn't call this an artistic choice; it's more of a visual expectation.

Personally, I'm *still* straddling the fence as to which scheme I personally
like, visually speaking; but I'll stick to assumed_gamma 1.0 and
'realistic/correct' lighting for now.

Btw, this is interesting:
In professional CGI environments, artists apparently work in a 'complete' and
rather austere  assumed_gamma 1.0 world-- even when using image_maps and the
like:
"Any input textures that are already gamma-corrected [like JPEGs] need to be
brought back to a linear color space before they can be used for shading or
compositing. Ordinary JPEG files viewed with Web browsers and the like will look
washed out. Film studios don't care if random images on the Internet look wrong



Wow.

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