Hugo wrote:
> 
> What's the catch in using gamma 1?

You have to be prepared to step into a higher level of consciousness.

Seriously, if you don't get it, don't stress about it.


_____________
Kari Kivisalo

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"Kari Kivisalo" wrote:
> The result is right, you just expect something else.

Isn't the whole point of gamma correction to assure a linear scale of
brightness or whatever it's called? So that when you specify a color that's
half as bright as another color, you really do percieve it that way when
looking at it?

What I'm saying is that when I specify a color of 10% brightness in relation
to white, I don't want to get a color that looks like it's of 60% brightness
in relation to white.

Could you explain your point further?

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:  http://rsj.mobilixnet.dk (updated Feb 16)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Ring:  http://webring.povray.co.uk

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> Remember that the monitor distorts your perception of
> the true relations in the scene. Without assumed_gamma
> you are seeing a distorted image.

This is what I mean. The monitor distorts the light and by using
assumed_gamma 2.2, the final result that hits my eye is correct.. (?)

> You have to be prepared to step into a higher
> level of consciousness. Seriously, if you don't
> get it, don't stress about it.

Hmm.. I am ready.. I know you're good at this light stuff. :o)

Regards,
Hugo

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Thank you!  I've been looking for this!

- Kevin R.

"Rune" <run### [at] mobilixnetdk> wrote in message
news:3c979331@news.povray.org...
> Yet another of those stacked plane cloud methods!
>
> On my website I've uploaded the code for the sky I'm using for my WIP
desert
> landscape image as seen in povray.binaries.images. I've gotten a request
for
> the code, and also saw a general request for stacked plane clouds here
> recently.
>
> My approach is not the most realistic maybe, but as it uses four planes
> only, it renders very fast.
>
> If you're interested, have a look at
> http://rsj.mobilixnet.dk/3d/goodies/goodies.html
>
> Please let me know what you think. :)
>
> Rune
> --
> 3D images and anims, include files, tutorials and more:
> Rune's World:  http://rsj.mobilixnet.dk (updated Feb 16)
> POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
> POV-Ray Ring:  http://webring.povray.co.uk
>
>

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Hugo wrote:
>
> The monitor distorts the light and by using
> assumed_gamma 2.2, the final result that hits my eye is correct..

I blame the docs. It's really the other way around. If your
display_gamma is 2.2 or not set, using assumed_gamma 2.2 does
nothing. assumed_gamma 1 corrects for gamma 2.2 display. At least
in 3.5.

> Hmm.. I am ready.. I know you're good at this light stuff. :o)

I hope so or the folks at luxlab.com will be really disappointed.
Ok, the laboratory was empty, I went there and now I'm pretending
to be the prof :)


_____________
Kari Kivisalo

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Kari Kivisalo wrote:
> I blame the docs. It's really the other way around. If
> your display_gamma is 2.2 or not set, using
> assumed_gamma 2.2 does nothing. assumed_gamma 1
> corrects for gamma 2.2 display. At least in 3.5.

I just read the Pov-docs about display_gamma.. Made me confused, but I think
display_gamma should be linked to that of my graphics card.. By default it's
2.2 when not specified in povray.ini (which it is not).. Assumed_gamma
should be 1.. This means, what appear on my monitor will be gamma corrected
on-the-fly but the image on disk will be non-gamma corrected.

This doesn't sound like a good idea for most people.. Almost every picture
we download from the net has already been gamma corrected, and would suffer
from further (such heavy) adjustments. I don't use windows-controlled gamma
correction, and I doubt many people do.

JRG wrote:
> The default finishes (esp. ambient is way too high)
> do not match well with assumed_gamma 1.

This doesn't sound similar to Kari Kivisalo? He seems to simply describe
another way of using the same amount of gamma correction.. So that shouldn't
change the way we use light and textures?

Regards  :o)
Hugo

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Hugo wrote:
> 
> I just read the Pov-docs about display_gamma.. Made me confused

The section on display_gamma points to 6.11.3 for more information on gamma.

6.11.3 Assumed_Gamma
---

no assumed_gamma in scene : 
   No gamma correction is applied to output file. 

assumed_gamma 1 : 
   Gamma Display_Gamma is applied to output file. 
   If Display_Gamma is not specified, 2.2 is used. 

assumed_gamma G : 
   Gamma Display_Gamma/G is applied to output file. 
   If Display_Gamma is not specified, 2.2/G is used. 

Recommended value for assumed_gamma is 1. 
---

The render window displays the image as it is written to file.
Radiosity works best with assumed_gamma 1 as will any feature
designed to simulate reality, like fresnel reflection.

Two tips to ease your path to enlightenment:

  Write rgb 0.2 instead of rgb 0.5 and rgb 0.03 instead of rgb 0.2.

  Don't hesitate to use image editor to enhance contrast at first.
  

Oh, and rgb 0.8 -> rgb 0.6 :)


_____________
Kari Kivisalo

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Thanks! From what I sense here, assumed_gamma 1 actually *activates* a gamma
correction of 2.2 in the output file, where the default assumed_gamma 2.2
becomes nothing because it gets divided with display_gamma 2.2.

Oh man! So instead of simulating gamma correction myself by using ordinary
rgb values, I should let the computer do this.. Yes, I understand this now!
Old rgb values should be ^ with 2.2 to get the new values ... but maybe it's
not so simple with finishs.. hmm.. but thank you!

Regards,
Hugo

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In article <3c98aca7$1@news.povray.org>, "Hugo" <hua### [at] post3teledk> 
wrote:

> Thanks! From what I sense here, assumed_gamma 1 actually *activates* a gamma
> correction of 2.2 in the output file, where the default assumed_gamma 2.2
> becomes nothing because it gets divided with display_gamma 2.2.
> 
> Oh man! So instead of simulating gamma correction myself by using ordinary
> rgb values, I should let the computer do this.. Yes, I understand this now!
> Old rgb values should be ^ with 2.2 to get the new values ... but maybe it's
> not so simple with finishs.. hmm.. but thank you!

With the finish statements that specify a brightness (reflection, 
ambient, diffuse, phong, specular), it should be similar. With 
statements that specify a size or falloff (brilliance, roughness, 
phong_size), it would be like "gamma correcting" the radius of a sphere, 
which is of course nonsense.
And don't forget your lights.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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I made the bumps a bit smaller and got a perfect desktop. Again simplicity
is beautiful. Thanks, Jonathan.  :)

Ari-Matti

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