Am 24.02.2016 um 18:32 schrieb ThH:

> Now for some more investigation... ;)

optics_mod_2.pov + pics

So far: Comment out 1 photon related command of your choice and the pics 
are optically identical.

Will continue...

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Attachments:
Download 'optics_mod_2.pov.txt' (2 KB) Download 'optics_mod_2_3.7.0.png' (82 KB) Download 'optics_mod_2_3.7.1.png' (87 KB)

Preview of image 'optics_mod_2_3.7.0.png'

Preview of image 'optics_mod_2_3.7.1.png'

Am 24.02.2016 um 18:10 schrieb Le_Forgeron:

> Just one year of patches to check...

Binary search FTW.

For starters, please focus on the commits that changed
`source/core/lighting/photons.cpp`, `source/core/material/media.cpp`,
and/or `source/core/render/trace.cpp`:

3c719d20822eae09e586fa5fb6685f7228872040 (3 Jan 2016)
a4c66a28ffdffe1296e44d1ad587ba93886ec925 (2 Jan 2016)
87de094585c4c8904b1c77124a4218567097dad4 (1 Jan 2016)
6d20f85957cca8e6acc22ad87485665524f363a9 (1 Jan 2016)
49835074f55e1027d97e7260b16bac43a6bc7059 (15 Nov 2015)
93b9ae98eaa28fdc1ada1ce9ccc59150fc037141 (12 Sep 2015)
3e93e2e2a1a4ccec034d7666d41f78ffb1ebf00f (11 Sep 2015)
04ed70261ff8cc1e2a02ec226a4fe0f1ef6177bf (5 Aug 2015)
117f215c5efb9e0d69703a520eff04713de72778 (5 Aug 2015) [p]
1b5aab60b0f15de4e8170bbec3820c5236c353d8 (27 Jun 2015)
6ed60adea3195995492635aa27c7c2db018717cc (5 Mar 2015) [m,t]

[p] I currently have no list of relevant commits to `photons.cpp` prior
to this one, as the file resided in a different location.

[m,t] I currently have no list of relevant commits to `media.cpp` and
`trace.cpp` prior to this one, as the files resided in a different location.

You may first want to check the following commit though; it is known to
build ok on Unix, and dates back just a few days earlier:

0c7f9773c6bbdd3bddcce2475d6e374ab2292ae6 (3 Mar 2015)

Note that some of the other commits may fail to compile on Unix. I trust
you to be able to deal with this one way or the other.

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Le 25/02/2016 03:49, clipka a écrit :
> Am 24.02.2016 um 18:10 schrieb Le_Forgeron:
> 
>> > Just one year of patches to check...
> Binary search FTW.

If only all commits were able to be compiled...

The problem is any commit
from 2014-06-14 14:26:48 +0200
to 2014-07-02 04:05:34 +0200

Far before any of your candidates.

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Attachments:
Download 'result.txt' (6 KB)

Am 25.02.2016 um 19:08 schrieb Le_Forgeron:
> Le 25/02/2016 03:49, clipka a écrit :
>> Am 24.02.2016 um 18:10 schrieb Le_Forgeron:
>>
>>>> Just one year of patches to check...
>> Binary search FTW.
> 
> If only all commits were able to be compiled...
> 
> The problem is any commit
> from 2014-06-14 14:26:48 +0200
> to 2014-07-02 04:05:34 +0200
> 
> Far before any of your candidates.

(Are you sure your list is complete? I do see more commits in between
those you cite, even on the same branch.)

The following look noteworthy to investigate:

changeset:   94:8e40f1a50cfd
parent:      92:e995e1ab7beb
parent:      93:a07181fe86db
user:        Christoph Lipka <c-l### [at] usersnoreplygithubcom>
date:        Thu Jun 19 10:24:56 2014 +0200
summary:     Merge branch 'master' into refactor

and then:

changeset:   96:f2d948f2a077
bookmark:    hotfix/photons_eca922a2
tag:         default/hotfix/photons_eca922a2
user:        Christoph Lipka <c-l### [at] usersnoreplygithubcom>
date:        Wed Jun 25 16:42:36 2014 +0200
summary:     fix photons bug introduced with commit
'eca922a2819fabbadd82c31e4bfadaa0c425b5b5'

In between these, we have a change in how photon colour/brightness data
is stored.

Do you think you can try to get these to compile by applying the Jun/Jul
2014 series of "GitHub issue #29" fixes to them?

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Am 26.02.2016 um 05:44 schrieb clipka:

> The following look noteworthy to investigate:
> 
> changeset:   94:8e40f1a50cfd
> parent:      92:e995e1ab7beb
> parent:      93:a07181fe86db
> user:        Christoph Lipka <c-l### [at] usersnoreplygithubcom>
> date:        Thu Jun 19 10:24:56 2014 +0200
> summary:     Merge branch 'master' into refactor
> 
> and then:
> 
> changeset:   96:f2d948f2a077
> bookmark:    hotfix/photons_eca922a2
> tag:         default/hotfix/photons_eca922a2
> user:        Christoph Lipka <c-l### [at] usersnoreplygithubcom>
> date:        Wed Jun 25 16:42:36 2014 +0200
> summary:     fix photons bug introduced with commit
> 'eca922a2819fabbadd82c31e4bfadaa0c425b5b5'
> 
> In between these, we have a change in how photon colour/brightness data
> is stored.

I think I'm up to something here.

The changes between these two commits are all about the encoded storage
of photons in an RGBE format, which is an adaptation of the floating
point idea to the domain of colours, using three independent mantissas
for the colour channels but a single shared exponent. This idea is also
at the core of the Radiance HDR image file format.

Photon storage and the Radiance HDR image file format use virtually the
same variation of the format, using 8-bit unsigned integers for both the
mantissas and the exponent, with the one exception that for photons an
exponent bias of 250 was chosen, while Radiance HDR uses a bias of 128.

Originally, the data type for photons storage was a simple C-style
4-element unsigned char array, with associated C-style global functions
for encoding and decoding. The Radiance HDR file format handling used
its own independent functions doing virtually the same thing.

Now in the aforementioned changes, this was refactored into a common
C++-style template class type for both photons and Radiance HDR code.

Having looked again at that changed code, I noticed some peculiarities
about the code that I didn't quite understand (yes, I know I wrote the
code myself ;)), and which I currently consider inferior, but I also
wasn't quite sure what that "photons bug introduced with commit
'eca922a2819fabbadd82c31e4bfadaa0c425b5b5'" was that had to be fixed
back then, and whether those peculiarities were there for a reason, so I
decided to revert those changes to revive that bug again.

I immediately recognized the resulting "optics.pov" render as the thing
that prompted me to implement the fix, so I'm sure again what it was all
about: In the process of refactoring I had made a slight "improvement"
that turned out to add a little bit of white light to otherwise pure
colours.

Now this doesn't look anything like what ThH has reported, nor what
you're seeing in your tests; but there is someting intriguing about it
that hadn't caught my attention back then:

It doesn't affect /all/ the rays.

As a matter of fact, it affects /exactly/ the very same subset of rays
as the issue now under investigation.


I think this is very strong evidence that the current issue is also
rooted in the RGBE handling code.

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Attachments:
Download 'optics.png' (284 KB)

Preview of image 'optics.png'

Am 24.02.2016 um 14:24 schrieb ThH:
> optics.pov from scenes/advanced...
> 
> The appended files had been rendered using povray V3.7.0 and Version
> 3.7.1-alpha.8492620.unofficial.

Can someone please test this version:

https://github.com/POV-Ray/povray/releases/tag/v3.7.1-alpha.8497793%2Bav110

I have no idea whether it will fix anything, but there is a glimmer of
hope that it just might.

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Am 27.02.2016 um 07:59 schrieb clipka:

> Can someone please test this version:
>
> https://github.com/POV-Ray/povray/releases/tag/v3.7.1-alpha.8497793%2Bav110
>
> I have no idea whether it will fix anything, but there is a glimmer of
> hope that it just might.

I wish you luck :)

The URL listed above leads to a Windows-Only-Thing, right?

Or did I miss any thing for NIXs ?

Thorsten aka ThH

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Am 27.02.2016 um 08:17 schrieb ThH:
> Am 27.02.2016 um 07:59 schrieb clipka:
>
>> Can someone please test this version:
>>
>> https://github.com/POV-Ray/povray/releases/tag/v3.7.1-alpha.8497793%2Bav110
>>
>>
>> I have no idea whether it will fix anything, but there is a glimmer of
>> hope that it just might.
>
> I wish you luck :)
>
> The URL listed above leads to a Windows-Only-Thing, right?
>
> Or did I miss any thing for NIXs ?
>
> Thorsten aka ThH

Shame on me...

NIXs meant Linux.

No to self:
No postings before first mug of tea!

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Am 27.02.2016 um 08:23 schrieb ThH:
> No to self:
> No postings before first mug of tea!

Darn me...

Meant:

Note to self

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Am 27.02.2016 um 08:17 schrieb ThH:
> Am 27.02.2016 um 07:59 schrieb clipka:
> 
>> Can someone please test this version:
>>
>> https://github.com/POV-Ray/povray/releases/tag/v3.7.1-alpha.8497793%2Bav110
>>
>>
>> I have no idea whether it will fix anything, but there is a glimmer of
>> hope that it just might.
> 
> I wish you luck :)
> 
> The URL listed above leads to a Windows-Only-Thing, right?

Nope; while the page the URL takes you to /does/ link to three pre-built
Windows binaries, it also leads to two source file packages, which
contain the entire source code for /all/ versions, including the Unix stuff.

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