I am rendering the same scene file with what I believe are the same 
settings on POV-Ray for Windows 3.5 and POV-Ray for Macintosh 3.6, but 
the PNG file that I get on the Mac is slightly darker than the PNG file 
generated on Windows.

Both testscene.pov files have a

global_settings {
    assumed_gamma setting 1.0
}

block. On Windows, my povray.ini file is set to Display_Gamma=2.0. On 
Macintosh, I have a testscene.ini file in the same directory as my 
testscene.pov file, and it also has a Display_Gamma=2.0 entry. And yet 
the Mac file still comes out darker.

What am I doing wrong? I'd like to be able to use both computers to 
split up an animation job I'm working on, but I can't have one set of 
PNG files coming out darker than the other. Help! Thanks.

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John Maynard wrote:
> Both testscene.pov files have a
> 
> global_settings {
>    assumed_gamma setting 1.0
> }
> 
> block.

Er, sorry... I meant to type that both files have a

global_settings {
    assumed_gamma 1.0
}

block... there is no "setting" word on that line. TIA...

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Will you search "GAMMA", which helps you.
Monitor gamma of Mac and WintelPC are different.

Y.Tanabe
Kobe,Japan

tec### [at] khrimorjp


John Maynard wrote:

> I am rendering the same scene file with what I believe are the same
> settings on POV-Ray for Windows 3.5 and POV-Ray for Macintosh 3.6, but
> the PNG file that I get on the Mac is slightly darker than the PNG file
> generated on Windows.
>
> Both testscene.pov files have a
>
> global_settings {
>     assumed_gamma setting 1.0
> }
>
> block. On Windows, my povray.ini file is set to Display_Gamma=2.0. On
> Macintosh, I have a testscene.ini file in the same directory as my
> testscene.pov file, and it also has a Display_Gamma=2.0 entry. And yet
> the Mac file still comes out darker.
>
> What am I doing wrong? I'd like to be able to use both computers to
> split up an animation job I'm working on, but I can't have one set of
> PNG files coming out darker than the other. Help! Thanks.

Post a reply to this message

In article <4042b05c$1@news.povray.org> , John Maynard 
<joh### [at] aolcom>  wrote:

> What am I doing wrong? I'd like to be able to use both computers to
> split up an animation job I'm working on, but I can't have one set of
> PNG files coming out darker than the other. Help! Thanks.

You need to enable gamma correction for your PC.  By default PC settings
display extremely bright images on screen.  This is the case for all
programs, not just POV-Ray.  You need to understand that the display gamma
setting is exactly there for this purpose, and setting it to the same value
on two systems with a different display gamma cannot possibly work.  You
need to set it to the true gamma of each system, not the same on both!

There is a lengthy section in the manual about setting the display gamma,
see section "5.2.2.2.2 Setting your Display Gamma".

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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Thank you for your reply, but I'm sorry; I don't think I was being 
clear. It's not just that the two files **look** different when viewed 
on a Macintosh vs. a Windows display--they ARE different. If I open up 
both files on my gamma-corrected Windows workstation in Paint Shop Pro 8 
and examine the RGB values for pixels at the same location on both 
files, the RGB values on the Mac file are **lower**. The PNG file being 
rendered by POV-Ray 3.6 doesn't just LOOK darker... it IS darker.

Thorsten Froehlich wrote:
> You need to enable gamma correction for your PC.  By default PC settings
> display extremely bright images on screen.  This is the case for all
> programs, not just POV-Ray.  You need to understand that the display gamma
> setting is exactly there for this purpose, and setting it to the same value
> on two systems with a different display gamma cannot possibly work.  You
> need to set it to the true gamma of each system, not the same on both!

I'm sorry, I must be misunderstanding you. Surely you are not saying 
that it is impossible to get a scene file to render exactly the same on 
Macintosh and Windows?

I don't give a fig that the Macintosh gamma is different from the 
Windows workstation--I do all my POV-Ray development on the Windows 
machine and the brightness for my scene has been set for the gamma on 
that machine. All that I want to do is fool the Macintosh into rendering 
the scene file so that it produces **exactly** the same resulting PNG 
file that I would get on the Windows machine. From reading the help file 
on Windows, it would seem that if I set assumed_gamma to 1.0, POV-Ray 
uses the Display_Gamma value that's stored in povray.ini (or 
<scenefilename>.ini on Macintosh). If the Display_Gamma is the same on 
both workstations, shouldn't I get exactly the same file on both 
workstations, or is this not possible with POV-Ray for Mac 3.6?

Thank you.

Post a reply to this message

> on Windows, it would seem that if I set assumed_gamma to 1.0, POV-Ray
> uses the Display_Gamma value that's stored in povray.ini (or
> <scenefilename>.ini on Macintosh).

Are you sure POV-Ray did read the INI file?  That is, you did specify it on
the command-line, didn't you?

    Thorsten

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Ack! No, with half the POV-Ray help file missing on the Macintosh, I was
relying on my own recollection of how to use INI files on the Mac. I thought
all you had to do was put a file with the same name as your *.pov file (but
with ".ini" on the end instead) in the same directory and POV-Ray would use
it.

Would you please tell me the POV-Ray Macintosh command line syntax for
specifying an INI file? Thank you!

"Thorsten Froehlich" <tho### [at] trfde> wrote in message
news:404349fe$1@news.povray.org...
> > on Windows, it would seem that if I set assumed_gamma to 1.0, POV-Ray
> > uses the Display_Gamma value that's stored in povray.ini (or
> > <scenefilename>.ini on Macintosh).
>
> Are you sure POV-Ray did read the INI file?  That is, you did specify it
on
> the command-line, didn't you?
>
>     Thorsten
>
>

Post a reply to this message

In article <40435683@news.povray.org> , "John Maynard" 
<joh### [at] aolcom> wrote:

> Ack! No, with half the POV-Ray help file missing on the Macintosh, I was
> relying on my own recollection of how to use INI files on the Mac.

There is no half missing:  The Mac specific part is not there, but that is
nothing unexpected for a beta version.  And the command-line usage is no
different from the Windows or online documentation anyway - because the
command-line parameters are of course the same for all versions of POV-Ray!

> Would you please tell me the POV-Ray Macintosh command line syntax for
> specifying an INI file? Thank you!

Sure, no problem:  You just specify the full file name on the command-line.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

Post a reply to this message

Thorsten Froehlich wrote:
 >>Would you please tell me the POV-Ray Macintosh command line syntax for
 >>specifying an INI file? Thank you!
 >
 > Sure, no problem:  You just specify the full file name on the 
command-line.
 >
 >     Thorsten

Thank you, that was very helpful. The files are now coming out 
**almost** the same on both computers, now that I'm using the same INI 
file on both machines with Display_Gamma=2.00 in both INI files.

There still appears to be a very slight difference between the outputted 
files, however. Although RGB pixel values are now pretty much the same 
all over, edge detail (anti-aliasing) looks like it's slightly different 
between the Mac and PC versions of the scene file. The Mac version looks 
slightly "smoother", for lack of a better description, but according to 
the INI file the anti-aliasing and jitter settings should be identical:

Input_File_Name=testscene.pov
Width=640
Height=480
Quality=9
Antialias=On
Antialias_Threshold=0.0
Sampling_Method=2
Antialias_Depth=2
Jitter=Off
Jitter_Amount=0.0
Output_Alpha=On
Output_File_Type=N
Warning_Level=0
Split_Unions=Off
Bounding_Threshold=25
Display=Off
Display_Gamma=2.00

The anti-aliasing differences seem to be more pronounced on shiny 
textures, especially ones that have normals with wrinkles. These aren't 
computed differently depending on the underlying CPU, are they? If not, 
the anti-aliasing algorithms are the same on the Mac and PC, aren't 
they? And they didn't change between POV-Ray 3.5 and 3.6, did they? 
Thank you.

Post a reply to this message

In article <404### [at] aolcom> , John Maynard 
<joh### [at] aolcom>  wrote:

> Although RGB pixel values are now pretty much the same
> all over, edge detail (anti-aliasing) looks like it's slightly different
> between the Mac and PC versions of the scene file

You should not be comparing two different versions of POV-Ray.
Anti-aliasing was changed a bit in POV-Ray 3.6.  Also note that even with
the same version and every setting absolutely identical, you cannot expect
to ever get an absolutely identical image.

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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