Hi all,

I rendered a very simple scene in both v3.62 and v3.7beta34:

camera{location <0,2,-2> look_at <0,0,0>}
light_source {<0,2,-2> color 1}
sphere{0,1 pigment{rgb<1,0,0>}}

If you render this scene in both versions, then it looks as if the sphere has
"flattened" in the new version.
Have certain default settings changed? Any ideas?

Thanks!
Cheers,
Frank

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On Sat, 22 Aug 2009 10:21:58 EDT, "Frank_C" <fra### [at] skynetbe> wrote:

>If you render this scene in both versions, then it looks as if the sphere has
>"flattened" in the new version.

Sorry but the only differences that I get in pigment which disappears when
adding  global_settings { assumed_gamma 1 } to the v3.62 scene.
-- 

Regards
     Stephen

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Stephen schrieb:
> On Sat, 22 Aug 2009 10:21:58 EDT, "Frank_C" <fra### [at] skynetbe> wrote:
> 
>> If you render this scene in both versions, then it looks as if the sphere has
>> "flattened" in the new version.
> 
> Sorry but the only differences that I get in pigment which disappears when
> adding  global_settings { assumed_gamma 1 } to the v3.62 scene.

Same here.

Frank, are you sure you used the same resolution with both renders?

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Stephen <mcavoysAT@aoldotcom> wrote:
> Sorry but the only differences that I get in pigment which disappears when
> adding  global_settings { assumed_gamma 1 } to the v3.62 scene.

  Btw, could someone explain, once again, why the default gamma settings
of povray 3.7 are different from the defaults in 3.6, making all scenes
without explicit gamma settings render differently? I never quite got the
reason for this.

-- 
                                                          - Warp

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Warp schrieb:
>   Btw, could someone explain, once again, why the default gamma settings
> of povray 3.7 are different from the defaults in 3.6, making all scenes
> without explicit gamma settings render differently? I never quite got the
> reason for this.

Maybe because they actually /do/ render identically, provided you 
specify "#version 3.6" to enforce backward compatibility?

Things only get complicated when you explicitly use a flexible-gamma 
file format (such as .png or .hdr). Having these render identically as 
well would probably require different "#version 3.6" defaults for the 
parameters of 3.7's gamma-handling mechanism. Or a nasty hack of that 
mechanism.

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clipka <ano### [at] anonymousorg> wrote:
> Warp schrieb:
> >   Btw, could someone explain, once again, why the default gamma settings
> > of povray 3.7 are different from the defaults in 3.6, making all scenes
> > without explicit gamma settings render differently? I never quite got the
> > reason for this.

> Maybe because they actually /do/ render identically, provided you 
> specify "#version 3.6" to enforce backward compatibility?

  That didn't really answer my question.

-- 
                                                          - Warp

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Warp schrieb:
>> Maybe because they actually /do/ render identically, provided you 
>> specify "#version 3.6" to enforce backward compatibility?
> 
>   That didn't really answer my question.

Of course it didn't - if the question is based on false observations and 
therefore moot, what point would there be in answering it?

That is, unless you are asking why the behavior is different when a 
#version statement is /not/ present. But in that case, there's no reason 
to favor compatibility over correctness: 3.6 default gamma handling was 
simply wrong (because it wasn't any gamma handling at all, thereby 
producing linear output where other software commonly expects 
gamma-precorrected files).

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clipka <ano### [at] anonymousorg> wrote:
> Stephen schrieb:
> > On Sat, 22 Aug 2009 10:21:58 EDT, "Frank_C" <fra### [at] skynetbe> wrote:
> >
> >> If you render this scene in both versions, then it looks as if the sphere has
> >> "flattened" in the new version.
> >
> > Sorry but the only differences that I get in pigment which disappears when
> > adding  global_settings { assumed_gamma 1 } to the v3.62 scene.
>
> Same here.
>
> Frank, are you sure you used the same resolution with both renders?


Hi!
I used indeed the same resolution settings for both renderings.
As Stephen indicated, the assumed_gamma keyword made both renders equal. However
I added an {assumed_gamma 2.2} in POV3.7 instead of an {assumed_gamma 1} in
POV3.62. This is because -on my PC- the latter setting had the effect of
"flattening" the sphere (or any other object).
Kind regards
Frank

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Frank_C schrieb:
> I used indeed the same resolution settings for both renderings.
> As Stephen indicated, the assumed_gamma keyword made both renders equal. However
> I added an {assumed_gamma 2.2} in POV3.7 instead of an {assumed_gamma 1} in
> POV3.62. This is because -on my PC- the latter setting had the effect of
> "flattening" the sphere (or any other object).

Ah, I see! I thought you meant geometric "flattening", but you're 
talking about colors.

Yes, gamma handling is significantly different between 3.6 and 3.7, and 
does lead to differences in color "intensity".

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clipka <ano### [at] anonymousorg> wrote:
> Frank_C schrieb:
> > I used indeed the same resolution settings for both renderings.
> > As Stephen indicated, the assumed_gamma keyword made both renders equal. However
> > I added an {assumed_gamma 2.2} in POV3.7 instead of an {assumed_gamma 1} in
> > POV3.62. This is because -on my PC- the latter setting had the effect of
> > "flattening" the sphere (or any other object).
>
> Ah, I see! I thought you meant geometric "flattening", but you're
> talking about colors.
>
> Yes, gamma handling is significantly different between 3.6 and 3.7, and
> does lead to differences in color "intensity".

Just for the completeness, here's a comparison between the two spheres.
The sphere on the left was created with version 3.6 and the sphere on the right
was rendered in version 3.7. I didn't use the assumed_gamma keyword here.

http://img41.imageshack.us/img41/5444/testgjc.png

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