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On 19 Nov 2001 05:15:30 -0500, Warp <war### [at] tag povrayorg> wrote:
> There's a bug in the current 3.5 beta. When writing to a PNG file, the wrong
>gamma correction value is written. AFAIK this has been fixed for the next beta.
Thanks for clarification. I wait.
ABX
--
#declare _=function(a,b,x){((a^2)+(b^2))^.5-x}#default {pigment{color rgb 1}}
union{plane{y,-3}plane{-x,-3}finish{reflection 1 ambient 0}}isosurface{ //ABX
function{_(x-2,y,1)|_((x+y)*.7,z,.1)|_((x+y+2)*.7,z,.1)|_(x/2+y*.8+1.5,z,.1)}
contained_by{box{<0,-3,-.1>,<3,0,.1>}}translate z*15finish{ambient 1}}//POV35
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>
> On Mon, 19 Nov 2001 12:14:11 +0200, Kari Kivisalo <ray### [at] engineercom> wrote:
> > Render the sky map image without assumed_gamma (linear).
> > Then in the scene where the image map is used put
> > assumed_gamma 1.
>
> And this not work
I just tested it and it works.
_____________
Kari Kivisalo
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On Mon, 19 Nov 2001 12:29:35 +0200, Kari Kivisalo <ray### [at] engineercom> wrote:
> > And this not work
>
> I just tested it and it works.
In my case
original scene, perspective camera, no assumed gamma -> 1.PNG
original scene, spherical camera, no assumed gama -> 2.PNG
new scene, perspective camera, 2.PNG as sky, no assumed gamma -> 3.PNG
new scene, perspective camera, 2.PNG as sky, assumed gamma 1.0 -> 4.PNG
new scene, perspective camera, 2.PNG as sky, assumed gamma 2.2 -> 5.PNG
1.PNG = 3.PNG
1.PNG != 4.PNG
1.PNG != 5.PNG
I compare image when POV-Ray displays it. Not with other software.
ABX
--
#declare _=function(a,b,x){((a^2)+(b^2))^.5-x}#default {pigment{color rgb 1}}
union{plane{y,-3}plane{-x,-3}finish{reflection 1 ambient 0}}isosurface{ //ABX
function{_(x-2,y,1)|_((x+y)*.7,z,.1)|_((x+y+2)*.7,z,.1)|_(x/2+y*.8+1.5,z,.1)}
contained_by{box{<0,-3,-.1>,<3,0,.1>}}translate z*15finish{ambient 1}}//POV35
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>
> original scene, perspective camera, no assumed gamma -> 1.PNG
> original scene, spherical camera, no assumed gama -> 2.PNG
> new scene, perspective camera, 2.PNG as sky, no assumed gamma -> 3.PNG
> new scene, perspective camera, 2.PNG as sky, assumed gamma 1.0 -> 4.PNG
> new scene, perspective camera, 2.PNG as sky, assumed gamma 2.2 -> 5.PNG
>
> 1.PNG = 3.PNG
> 1.PNG != 4.PNG
> 1.PNG != 5.PNG
It's supposed to go like this:
> original scene, perspective camera, assumed_gamma 1 -> 1.PNG
> original scene, spherical camera, no assumed gama -> 2.PNG
> new scene, perspective camera, 2.PNG as sky, assumed gamma 1.0 -> 4.PNG
> 1.PNG = 4.PNG
If you wan't the final image gamma corrected you must design also
the sky as gamma corrected.
_____________
Kari Kivisalo
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On Mon, 19 Nov 2001 12:59:47 +0200, Kari Kivisalo <ray### [at] engineercom> wrote:
> > 1.PNG = 3.PNG
> > 1.PNG != 4.PNG
> > 1.PNG != 5.PNG
>
> It's supposed to go like this:
> If you wan't the final image gamma corrected you must design also
> the sky as gamma corrected.
That's what I don't understand. If I don't specify assumed_gamma I expect some
default value of it. And documentation says (6.11) it has default value equal to
display_gamma which is default equal 2.2 on windows platform. So I expect no
assumed gamma is equvalent for assumed_gamma 2.2 (eventually 1.0 as linear
copying of sky).
ABX
--
#declare _=function(a,b,x){((a^2)+(b^2))^.5-x}#default {pigment{color rgb 1}}
union{plane{y,-3}plane{-x,-3}finish{reflection 1 ambient 0}}isosurface{ //ABX
function{_(x-2,y,1)|_((x+y)*.7,z,.1)|_((x+y+2)*.7,z,.1)|_(x/2+y*.8+1.5,z,.1)}
contained_by{box{<0,-3,-.1>,<3,0,.1>}}translate z*15finish{ambient 1}}//POV35
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>
> That's what I don't understand.
This is how gamma in povray works.
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.
_____________
Kari Kivisalo
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On Mon, 19 Nov 2001 13:27:24 +0200, Kari Kivisalo <ray### [at] engineercom> wrote:
> This is how gamma in povray works.
Thanks, if it is all true it is best ascetic tutorial about it :-)
Why it can't be described within documentation this short way ?
ABX
--
#declare _=function(a,b,x){((a^2)+(b^2))^.5-x}#default {pigment{color rgb 1}}
union{plane{y,-3}plane{-x,-3}finish{reflection 1 ambient 0}}isosurface{ //ABX
function{_(x-2,y,1)|_((x+y)*.7,z,.1)|_((x+y+2)*.7,z,.1)|_(x/2+y*.8+1.5,z,.1)}
contained_by{box{<0,-3,-.1>,<3,0,.1>}}translate z*15finish{ambient 1}}//POV35
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Try using another image format (eg. tga) and see if the problem still happens
there. If it doesn't happen, then the problem is simply the wrong PNG gamma
correction value. If it does, then the problem is somewhere else.
--
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}// - Warp -
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Skiba wrote:
> Why it can't be described within documentation this short way ?
>
It will be.
Ingo
--
Photography: http://members.home.nl/ingoogni/
Pov-Ray : http://members.home.nl/seed7/
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On Mon, 19 Nov 2001 13:27:24 +0200, Kari Kivisalo <ray### [at] engineercom> wrote:
>Recommended value for assumed_gamma is 1.
But there is another question: what is the fastest way of adjusting designed
enviroment_map to be rerendered with assumed_gamma 1? Adjusting could be started
from calculated factor for color values? How calculate this ?
ABX
--
#declare _=function(a,b,x){((a^2)+(b^2))^.5-x}#default {pigment{color rgb 1}}
union{plane{y,-3}plane{-x,-3}finish{reflection 1 ambient 0}}isosurface{ //ABX
function{_(x-2,y,1)|_((x+y)*.7,z,.1)|_((x+y+2)*.7,z,.1)|_(x/2+y*.8+1.5,z,.1)}
contained_by{box{<0,-3,-.1>,<3,0,.1>}}translate z*15finish{ambient 1}}//POV35
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