"clipka" <nomail@nomail> wrote:

> > Sorry for the trivial question but
> > - I've tried ot used assumed_gamma 2.2 in the pov file
> > - I've tried ot used Display_Gamma=2.2 in the pov file
> > - I've tried to add it to the povray command-line "Display_Gamma=2.2"
> > - I've tried to add it to the povray command-line "Display_Gamma=2.2
> > File_Gamma=2.2" (like in scenes/incdemo/glasses/glass.pov)
> >
> > Without any luck.
>
> Please be more specific:
> (1) What is your actual problem?

I would like to render a file (generated using VMD ->
http://www.ks.uiuc.edu/Research/vmd/) and get the same rendering with 3.6 and
3.7 for comparison (i've used transparency on it and i cannot be sure where the
difference in rendering comes from Gamma or else).

> (2) Are we talking about preview, or file output?

Both, but preferably file output.

> (3) If file output, what file type?

targa (.tga).


> In addition, the behavior depends on which "#version" you choose in the scene
> file.

There is no define, only a header stating:
// POV 3.x input script : plot.pov
// try povray +W1590 +H1066 -Iplot.pov -Oplot.pov.tga +P +X +A +FT +C
#if (version < 3.5)
#error "POV3DisplayDevice has been compiled for POV-Ray 3.5 or above.\nPlease
upgrade POV-Ray or recompile VMD."
#end


> > I've also searched the source code for it but so far i'm not expert in using the
> > defaults, but the changelog mentions "Added "File_Gamma" INI option" which i
> > have not found at the moment.
> >
> > Any hint?
>
> All command line / INI options are defined in "processrenderoptions.cpp"; you
> will find "Display_Gamma" there between "Display" and "Draw_Vistas", and
> "File_Gamma" between "Field_Render" and "Final_Clock".
>
> The values are read in using a framework; you will find references to the
> "kPOVAttrib_XYZ" identifiers - e.g. "kPOVAttrib_DisplayGamma" and
> "kPOVAttrib_FileGamma" - in the code actually evaluating these (in this case a
> template in "renderfrontend.h"); from there, dig up the road to modules such as
> png.cpp...

ok, found them, but in fact i was not clear. I would like to keep the code as it
is, but how can i alter on the command line the behaviour ?

I would like to do:
(1) povray3.7 plot.pov ... -> 3.7 rendering with new gamma correction
(2) povray3.7 GammaParameter=2.2 -> 3.7 rendering with no gamma correction

This is in order to see if the differences i'm seing between 3.7 and 3.6
rendering comes only from the Gamma processing, or from something else (that i
should report in the forum and/or upstream to the VMD developper).

I could attach some files but each of them is around 18MB (uncompressed), so
before going to this, i'll prefer asking the simple point here:
- is it possible to tweak povray3.7beta to mimic the 3.6 behaviour (concerning
the gamma rendering, of course), with a command line or specicif .ini?

Thanks a lot for your work, patience and dedication (i'm using povray + vmd for
more than 8 years now, but i'm just starting contributing...).

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