"Kenneth" <kdw### [at] gmailcom> wrote:
>
> I would suggest simply changing the specified colors to srgb
> versions-- no fancy conversions-- and see what it looks like at assumed_gamma
> 1.0.
>

I decided to try that myself, for the S_Cloud1 skysphere. It makes use of the
pigments P_Cloud2 and P_Cloud3 in "skies.inc", so I changed those as well. All
srgb colors now, with assumed_gamma 1.0.

SO...the result is not what I was naively expecting; very different from the
v3.6 assumed_gamma 2.2 version. Rather stark and ugly.

I guess my 'simple' color/gamma conversion scheme is not the way to proceed...
:-[

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"Kenneth" <kdw### [at] gmailcom> wrote:
> Just as a check, I rendered your example  SCloud_1  skysphere in v3.8xx
> (assumed_gamma 1.0), and get identical results to your middle image. So far, so
> good ;-)
>

Hmm, they are not quite identical after all.

I thought I would do a side-by-side comparison of your v3.6 assumed_gamma 1.0
version to v3.8xx (I changed the "skies.inc" pigments back to their originals.)

There's a definite difference; I assume that it comes from the many
'under-the-hood' changes made to POV-ray since v3.6.

So it seems to be very difficult to determine (and update) what the author's
*original* visual intent was for these pigments.

Unless we all go back to using v3.6  :-O

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Le 2021-02-28 à 03:14, Thomas de Groot a écrit :
> I am currently browsing through the include files to see if I can give a 
> meaningful contribution to their upgrading to 3.7+ standard. Over time, 
> some have been added to or partly upgraded, some are in am almost 
> pristine state going back to version 3.1.
> 
> I started small and upgraded skies.inc, using the scene files provided 
> in scenes/textures/pigments/skies.
> 

Another thing.
Most if not all of those are using ambient for the clouds. That need to 
be changed to emission to work properly in a radiosity scene.

The same hold for the starry skies.

Next, the ambient component in the metallic textures need to go away.

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Op 28/02/2021 om 16:09 schreef Kenneth:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>>
>> I would suggest simply changing the specified colors to srgb
>> versions-- no fancy conversions-- and see what it looks like at assumed_gamma
>> 1.0.
>>
> 
> I decided to try that myself, for the S_Cloud1 skysphere. It makes use of the
> pigments P_Cloud2 and P_Cloud3 in "skies.inc", so I changed those as well. All
> srgb colors now, with assumed_gamma 1.0.
> 
> SO...the result is not what I was naively expecting; very different from the
> v3.6 assumed_gamma 2.2 version. Rather stark and ugly.
> 
> I guess my 'simple' color/gamma conversion scheme is not the way to proceed...
> :-[
> 

This is strange. Attached find my version of the same which is 
comparable to the original. Something is different apparently.

In skies.inc, I also changed the version to 3.7, which is also used in 
the scene file.

-- 
Thomas

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Op 28/02/2021 om 18:11 schreef Alain Martel:
> Le 2021-02-28 à 03:14, Thomas de Groot a écrit :
>> I am currently browsing through the include files to see if I can give 
>> a meaningful contribution to their upgrading to 3.7+ standard. Over 
>> time, some have been added to or partly upgraded, some are in am 
>> almost pristine state going back to version 3.1.
>>
>> I started small and upgraded skies.inc, using the scene files provided 
>> in scenes/textures/pigments/skies.
>>
> 
> Another thing.
> Most if not all of those are using ambient for the clouds. That need to 
> be changed to emission to work properly in a radiosity scene.
> 
> The same hold for the starry skies.
> 
> Next, the ambient component in the metallic textures need to go away.

Yes sir. One of the first actions I took in skies.inc was to change 
ambient to emission. It has also the neat advantage that it works 
correctly whether radiosity is used or not.

The stars.inc file has a very different type of problem about which I 
shall write separately. As it stands now, it is totally useless.

Otherwise, indeed, ambient needs to be dropped completely.

-- 
Thomas

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Op 28/02/2021 om 16:43 schreef Kenneth:
> "Kenneth" <kdw### [at] gmailcom> wrote:
>> Just as a check, I rendered your example  SCloud_1  skysphere in v3.8xx
>> (assumed_gamma 1.0), and get identical results to your middle image. So far, so
>> good ;-)
>>
> 
> Hmm, they are not quite identical after all.
> 
> I thought I would do a side-by-side comparison of your v3.6 assumed_gamma 1.0
> version to v3.8xx (I changed the "skies.inc" pigments back to their originals.)
> 
> There's a definite difference; I assume that it comes from the many
> 'under-the-hood' changes made to POV-ray since v3.6.
> 
> So it seems to be very difficult to determine (and update) what the author's
> *original* visual intent was for these pigments.
> 
> Unless we all go back to using v3.6  :-O
> 

I have not tested it, but maybe your differences come from the fact that 
you use version 3.8 here. I did not, from the principle that version 3.7 
and/or 3.7.1 are the /last/ official versions of POV-Ray. As a start, 
the includes should comply with those versions. Version 3.8 is beta and 
may need more changes in future.

-- 
Thomas

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Op 28/02/2021 om 14:52 schreef Bald Eagle:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> I am currently browsing through the include files to see if I can give a
>> meaningful contribution to their upgrading to 3.7+ standard. Over time,
>> some have been added to or partly upgraded, some are in am almost
>> pristine state going back to version 3.1.
> 
> Thanks, Thomas.
> I still have a few include files from Friedrich Lohmueller that I was working
> through to tighten up the code and try to explain what was going on.
> 
> 
>> The fundamental question is: What do we want?
> 
> Short answer: you really can't ever tell.
> You may want to somehow include all three.
> CloudySky1
> CloudySky2
> CloudySky3
> 
> Or maybe put all 3 versions in a macro with a version argument, and use #switch
> to pick which one gets used.
> 

Indeed. This was one of the options I was thinking about. However, as 
you correctly mentioned below, these files are (probably) mostly used as 
reference and learning items, and their value resides in the first place 
to their use by new users. So, I would prefer to update/-grade the files 
to 3.7.1 standards. In the process, some files will probably need more 
serious tweaking than others or be completely rewritten. A #switch kind 
of system may then be advisable indeed, as you write below (and above).

> 
> Very long version:
> 

And I appreciate your effort. I am not going to comment in detail just 
now, but keep this in the background as reference.

> 
> I try to keep in mind that these files are accessed for usage, reference, and
> learning.
> So, the way I (try to) approach my stuff, is a chaotic mix of the following:
> 
> 1. The simplest bare-bones example whose text can be used in the copy-paste
> mechanism of the Insert Menu.
> Because Whether I'm tired or forgetful, or whatever - I approach this part from
> a New User perspective, and just want to plug in some working code from the GUI.
> 
> The only "extra" here, is that for something like a macro, I like to write a
> working line of code or two to illustrate its actual usage in a scene.
> 
> 2. Since these might be used as a reference to how certain features work, or as
> the basis for the development of new SDL, or just as a historical record of
> POV-Ray development, I like to get rid of "magic numbers", give things
> meaningful identifiers, and perhaps restructure the formulas and code a bit so
> that it's neat, clean, and easy to follow.
> Author, date, version number, revision comments, etc.
> This might comprise a completely separate "meta-version" of the code, which has
> #debug statements enabled by #if_def (Verbose), etc.
> 
> One thing I've toyed with but haven't really fleshed out and used extensively,
> if to come up with a naming scheme for almost everything, so that 400 lines into
> some complicated scene code, I can get a clue about what's going on, and jump a
> few steps ahead in the debugging process.
> f_Identifier - function
> v_Identifier - vector quantity
> s_Identifier - scalar quantity
> C_Identifier - color
> P_Identifier - Pigment
> T_Identifier - Texture
> L_Identifier - a loop variable: #for (L_Identifier, 0, 10)
> 
> If Verbose is defined (boolean), I may send some comments to the debug stream
> showing that a macro has indeed been invoked, and has exited.  That's just
> because a scene with a large number of nested things can get pretty crazy,
> trying to figure out where things went wrong.  Looking at the debug stream, I
> can count the number of opening and closing statements and see where things went
> off the rails.
> 
> For complicated formulas, or ones that probably won't have obvious meaning, a
> few comments on what it does, how it's composed, what the assumed inputs and
> outputs are, and perhaps a reference to the origin of the formula can go a long
> way.
> // based on code / formula for [whatever] - POV-Ray, Graphics Gems, ShaderToy,
> website URL, math textbook, etc.
> // Takes 2 vectors and uses the point-slope formula for a line to....
> // divide both sides by x and cancel out [term] ....
> 
> 
> On rare occasion, just for kicks, I've sent the stepwise solution to the worked
> problem to the debug stream.
> 
> Along those lines, you might not worry so much about which fish to give the
> end-user, and instead include a texture-generating macro that teaches someone
> how a nice sky texture gets generated from first principles.
> Links to the wiki for various features ought to help people quickly grasp what's
> going on and possibly avoid the rehashing of the usual "how do I...", and even
> if they do ask, anyone can just post a quick and simple "Just look at
> m_ExampleMacro () in skies.inc - it _shows_ you how to do _everything_ ...
> 
> If you use "Step" as a macro argument, then you could progressively step through
> the code line-by-line by doing something like
> #if (Step > 0)
> #declare P_SkyBasis = pigment {bozo};
> #end
> #if (Step > 1)
> #declare P_StretchedSky = pigment {P_SkyBasis scale <10, 1, 50>}
> #end
> 
> etc.
> Every increment to step executes ALL of the previous steps.
> Of course, you could use clock as well...
> 


-- 
Thomas

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Op 01/03/2021 om 08:49 schreef Thomas de Groot:
> Op 28/02/2021 om 16:43 schreef Kenneth:
>> "Kenneth" <kdw### [at] gmailcom> wrote:

>>> (assumed_gamma 1.0), and get identical results to your middle image. 
>>> So far, so
>>> good ;-)
>>>
>>
>> Hmm, they are not quite identical after all.
>>
>> I thought I would do a side-by-side comparison of your v3.6 
>> assumed_gamma 1.0
>> version to v3.8xx (I changed the "skies.inc" pigments back to their 
>> originals.)
>>
>> There's a definite difference; I assume that it comes from the many
>> 'under-the-hood' changes made to POV-ray since v3.6.
>>
>> So it seems to be very difficult to determine (and update) what the 
>> author's
>> *original* visual intent was for these pigments.
>>

>>
> 
> I have not tested it, but maybe your differences come from the fact that 
> you use version 3.8 here. I did not, from the principle that version 3.7 
> and/or 3.7.1 are the /last/ official versions of POV-Ray. As a start, 
> the includes should comply with those versions. Version 3.8 is beta and 
> may need more changes in future.
> 

I tested and, no, you must have used some wrong settings somewhere. 
versions 3.7 or 3.8 render identically.

-- 
Thomas

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Thomas de Groot <tho### [at] degrootorg> wrote:

> >
> > I have not tested it, but maybe your differences come from the fact that
> > you use version 3.8 here. I did not, from the principle that version 3.7
> > and/or 3.7.1 are the /last/ official versions of POV-Ray. As a start,
> > the includes should comply with those versions. Version 3.8 is beta and
> > may need more changes in future.
> >
>
> I tested and, no, you must have used some wrong settings somewhere.
> versions 3.7 or 3.8 render identically.
>
You are absolutely correct; I made a mistake, a really dumb one: In my simple
v3.8xx scene file for testing the skysphere and the rgb-vs-SRGB colors, I
mistakenly wrote #version 2.8 instead of 3.8! (I have no idea what "version 2.8"
does to colors-- if there ever WAS such a version.) My render was definitely
screwed up; sorry for the confusion.

Now, my v3.8 SRGB-color version looks just like your v3.7 version.

I also ran my scene in v3.7 to double-check any color/gamma differences
between that and v3.8xx; they look identical, as you say.

The other interesting behavior I noticed (maybe it's expected) is that the older
#version directive of 3.5 in "skies.inc" can be changed to 3.7, with absolutely
no change in the renders (when run in either v3.7.0 or 3.8xx). I did some
'difference' comparisons in Photoshop to check this.

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"Kenneth" <kdw### [at] gmailcom> wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
> >
> > I would suggest simply changing the specified colors to srgb
> > versions-- no fancy conversions-- and see what it looks like at assumed_gamma
> > 1.0.
> >
>
> I decided to try that myself, for the S_Cloud1 skysphere...

This is what the comparison was supposed to look like, between
v3.6 at assumed_gamma 2.2
and
v3.7.0 (or 3.8, same effect) at assumed gamma 1.0

There is a slight difference, perhaps in contrast. It is difficult to figure out
exactly what causes this; but it might be like comparing 'apples to oranges',
considering the many changes that have been made to POV-ray since v3.6.

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