Hi.

If, for the rendering of a scene, I use:

global_settings { assumed_gamma 1 }
Display_Gamma=1

and assuming that the scene is dim enough so there will be no clipping.

If I make the scene twice as bright, by doubling the value of all lights and
ambient values, can I expect that the resulting rendered scene will have all
the pixel values doubled?

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Nicolas George <nicolas$george@salle-s.org> wrote:
> If I make the scene twice as bright, by doubling the value of all lights and
> ambient values, can I expect that the resulting rendered scene will have all
> the pixel values doubled?

  There may be other things besides light sources and ambient light which
affects the color of the pixels. Media is one example.

-- 
                                                          - Warp

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Warp  wrote in message <481ddb4e@news.povray.org>:
>   There may be other things besides light sources and ambient light which
> affects the color of the pixels. Media is one example.

Right, there are emitting media, I forgot them.

But if I handle all kinds of light sources, it should be linear, right?

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> But if I handle all kinds of light sources, it should be linear, right?

There are saturation issues if you use bright lights, you can end
up with pixels that are brighter than displayable, which washes out
the highlights. High Dynamic Range Images (HDRI) are not supported
in 3.61, though they are supported in MegaPOV. Also there are
gamma correction issues... a pixel that is half the value of another
pixel is not necessarily half the brightness, it's modified a bit by
hardware. You might try making a test pattern with some
gradient pigments to check the how linear the image gamma
appears with different assumed_gamma values.

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"Tim Attwood"  wrote in message <481e48b0$1@news.povray.org>:
> There are saturation issues if you use bright lights

Of course. I explicitly excluded these case in my original question.

My goal is to make the scene dimmer than it should be, and then post-process
it to simulate glare effects.

>						 Also there are
> gamma correction issues...

As I wrote, I intend to put both scene gamma and output gamma to 1.

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