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"Rune" <run### [at] mobilixnet dk> ha scritto nel messaggio
news:3c97b9c3@news.povray.org...
> "Christoph Hormann" wrote:
> > There is no complete shadow in your scene and with a
> > light source of color rgb 3 you should expect it being bright.
>
> You seem to assume I'm talking about that cloud scene? I'm not. This is my
> test scene:
>
> // global_settings{assumed_gamma 1}
> light_source {<1,2,-2>*100, rgb 1}
> sphere {3*z, 1 pigment {rgb 1}}
The default finishes (esp. ambient is way too high) do not match well with
assumed_gamma 1.
This worked for me:
global_settings {
ambient_light 0
assumed_gamma 1
}
#declare White_Texture =
texture {
pigment {
rgb 1}
finish {
ambient 0
diffuse 0.75
specular 0.65
roughness 0.008
reflection {0.03,1 falloff 5}
}
normal {
bumps 0.05 scale 1}
}
sphere {
3*y+5*z,3
texture {
White_Texture scale 0.08}
}
plane {y,0
pigment {rgb 0}
finish {ambient 0
diffuse 0.8 specular 0.5 roughness 0.01 reflection 0.2
}
}
light_source {
<0,140,0>
rgb 1
area_light 30*x,30*z,5,5 adaptive 0 jitter circular orient
fade_power 2
fade_distance 100
}
light_source {
<-30,80,-99>
rgb 1
area_light 10*x,10*y,5,5 adaptive 0 jitter circular orient
fade_power 2
fade_distance 120
}
light_source {
<0,50,99>
rgb 0.8
area_light 10*x,10*y,5,5 adaptive 0 jitter circular orient
fade_power 2
fade_distance 100
}
#version 3.1;
camera {
location <0,25,-40>
right image_width/image_height*x
look_at 5*y
angle 20
rotate 5*y
}
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> When simply using assumed_gamma 1, the results I get are wrong.
I fully agree. What's the catch in using gamma 1? I have read about these
things but I don't see any benefit of stepping away from 2.2
Thanks for sharing the cloud code Rune! :o)
Regards,
Hugo
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Rune wrote:
>
> When simply using assumed_gamma 1, the results I get are wrong.
The result is right, you just expect something else. Remember
that the monitor distorts your perception of the true relations
in the scene. Without assumed_gamma you are seeing a distorted
image.
When using assumed_gamma 1, one tends to build scenes with fixed
contrast ratio so they will look good without post processing.
This limits the scenes somewhat but no more than before. It will
train the eye to see the true relations in a scene, which is
valuable knowledge. It will enable you, with post processing, to
build scenes in a wide range of contrast ratios.
_____________
Kari Kivisalo
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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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