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16 Aug 2022 08:47:18 EDT (-0400)
  weird white stain with beta povray v3.8.0 (not with povray v3.7.0) (Message 11 to 20 of 23)  
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From: Kenneth
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 18 Jan 2022 09:35:00
Message: <web.61e6cfd9c82cc78e4cef624e6e066e29@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
>
> Good detective work!  :)
>
Thanks, Cousin Walker! I've been experimenting a LOT with rad over the past 6
months, kind of 'deconstructing' its many variables and how they interact. Test
after test after...

I have not really taken a deep look at Warren's code; there's a lot of
'busy-ness' in the many include files to chew through.

I think the 'heart' shape is due to just a particular juxtaposition of objects
and lights, as 'processed' by the rad settings. They can take on some pretty
weird shapes sometimes, depending on scene geometry.

BTW, I never did a complete *finished* render of this code. Running it as-is
with no changes, the render almost stalls about 2/3 of the way through-- and
this on my 8 core/16 thread machine! I never did figure out the cause. The
pumpkin lights? The candles? Something is causing my machine to churn through
almost endless calculations. For my tests, I had to turn off at least the
pumpkins.


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From: Warren
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 19 Jan 2022 06:45:00
Message: <web.61e7f96cc82cc78e1d602a3e756b296@news.povray.org>
> "Bald Eagle" <cre### [at] netscapenet> wrote:
> BTW, I never did a complete *finished* render of this code. Running it as-is
> with no changes, the render almost stalls about 2/3 of the way through-- and
> this on my 8 core/16 thread machine! I never did figure out the cause. The
> pumpkin lights? The candles? Something is causing my machine to churn through
> almost endless calculations. For my tests, I had to turn off at least the
> pumpkins.

Hello / Hi
The scene stalls at 2/3 percent because of the well isosurface (it is a cylinder
parametric function with an add of customized crackle pattern. In addition, I
deleted the heavy-weight tree mesh in the archive posted in 'binaries' forum
section. I you want the complete scene or just take a look at the final image,
you should take a look at my web site:
"https://www.ant01.fr/index.php/graphismes/stills-natures-mortes-avec-povray".
But I didn't update the archive you can download from there.
Since the first posts of Kenneth and William F. Pokorny , I tested the changes
they suggested (replace srgb with rgb in some cases mainly) but the renders were
not exempt of bugs, unfortunately, excepted for some renders with povray
v3.7.0.8.

I think I pointed out a bug, but I've no idea of where it comes from.


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From: Kenneth
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 20 Jan 2022 08:25:00
Message: <web.61e96191c82cc78e4cef624e6e066e29@news.povray.org>
I decided to go through all of the scene's include files-- turning off all of
the light sources, correcting any out-of-gamut srgb colors to 1.0 max, and
eliminating every object except the pentagram and the ground.

And I was still seeing the bright radiosity patches :-(

So I made my own VERY simplified scene-- posted below-- using just the bare
necessities of Warren's code plus a few simplifications... and finally
discovered what I think are the root causes of those bright patches. There are
THREE reasons, as far as I can tell:

1) The sky-sphere object is the primary cause. Comment-out that sphere, and the
problem patches disappear.

2) Radiosity's 'media ON' switch is also a primary problem; turn that OFF and
the patches disappear.

3) The media-pentagram is, I think, halfway embedded in the ground; that seems
to definitely be adding to the problem, for some reason. Move it even slightly
upward (like William P. mentioned), and the number of bright patches greatly
decreases. Not completely, though, as 1) and 2) still produce some patches at
random.

I don't know what is going on with rad's 'media on' switch; but the sky-sphere
problem does not make any sense to me, as its colors are only 0.3 maximum...
certainly not 'super bright'.

Maybe others here have some additional clues?

---------
// 1/19/22-- reduced version of Warren's 'HallowHouseScene' code,
// by Ken Walker

#version 3.7;

#declare RAD_ON = true;
#declare P_start = 64 / image_width;
#declare P_end_final = 4 / image_width;
#declare GroundScale = < 80, 1, 160 >;

global_settings{
assumed_gamma 1.0

#if(RAD_ON)
radiosity{ // mostly Warren's settings
pretrace_start P_start
pretrace_end   P_end_final
error_bound 0.2
minimum_reuse 0.09 // Ken
maximum_reuse 0.091 // Ken
nearest_count 9
count 800
recursion_limit 1
always_sample off
gray_threshold 0.6
brightness 1
adc_bailout 0.01/2
normal on
media on // [If OFF, that ELIMINATES the super-bright radiosity patches.]
         }
#end
}

camera{
 location<-24,6,-24>
 look_at <6, 5, 0>
}


background{color srgb 0.05}

// This light is NOT the cause of the bright radiosity patches.
light_source{<-2,4,-3 >*1000000 color srgb <0.5,0.5,0.6>*0.75 }


#declare SkyPigment =
pigment{
    gradient y
    color_map{
        [0.0 color srgb 0]
        [0.75 color srgb <0.075, 0.075, 0.15>]
             }
}

// ---- THIS SPHERE IS THE MAIN CAUSE OF THE SUPER-WHITE RAD PATCHES (along
// with 'media on' in the rad block) ---

sphere{0, 1
    pigment{ SkyPigment }
    finish{ diffuse 0 emission <1,1,0.95>*0.3}
    scale 4000000
    hollow on
    no_shadow
    no_image
    no_reflection
}

#declare RedCol = color srgb <255,40,0 >/255;
#declare OrangeCol = color srgb <255,155,0 >/255;
#declare Clear = color srgbft <0,0,0,0,1>;
#declare FireMix =
density{
    wrinkles
    density_map{
        [0.4 RedCol ]
        [0.5 OrangeCol]
        [0.6 RedCol]
        }
     }

#declare PointsNumber = 5;
#declare PentagramRadius = 4;
#declare PentagramScaleFactor = 12/PentagramRadius/2;
#declare LineRadius = 0.01;

#declare PentagramCirclePoints = array[PointsNumber]
{<0,0,0>, <0,0,0>, <0,0,0>, <0,0,0>, <0,0,0> }

#for( It, 0, PointsNumber - 1 )
#declare PentagramCirclePoints[It] = <0,0,PentagramRadius>;
#declare PentagramCirclePoints[It] = vrotate(PentagramCirclePoints[It],
< 0,360/PointsNumber*It,0>);
#end

//Link pentagram points
#declare Pentagram =
union{
torus{ PentagramRadius, LineRadius sturm }
cylinder{ PentagramCirclePoints[0], PentagramCirclePoints[2], LineRadius }
cylinder{ PentagramCirclePoints[0], PentagramCirclePoints[3], LineRadius }
cylinder{ PentagramCirclePoints[1], PentagramCirclePoints[3], LineRadius }
cylinder{ PentagramCirclePoints[1], PentagramCirclePoints[4], LineRadius }
cylinder{ PentagramCirclePoints[2], PentagramCirclePoints[4], LineRadius }
     pigment{ color srgbft <0, 0, 0, 0, 1> }
     hollow
     no_shadow
     interior{
         media{
             emission
             color srgb 8 // This is not the major problem; change
                          // to 0.1 to see
             samples 30
             intervals 1
             density{bozo scale 0.1}
  }
 }
    //translate (.03 - .04*clock)*y // moving the pentagram away from the
    // GROUND reduces the number of super-bright radiosity splotches--
    // I think the pentagram is halfway embedded in the ground.
}


#declare brown1_srgb = color srgb <122, 72, 57> / 255;
#declare brown2_srgb = color srgb <126, 76, 62> / 255;
#declare brown3_srgb = color srgb <114, 62, 53> / 255;
#declare brown4_srgb = color srgb <102, 53, 43> / 255;
#declare brown5_srgb = color srgb <93 , 43, 38> / 255;

#macro T_5var_Wrinkles( multiplicateur, Col1, Col2, Col3, Col4, Col5)
texture{
      pigment{
       wrinkles
       color_map{
          [0.0 Col3*multiplicateur]
          [0.125 Col2*multiplicateur]
          [0.25 Col1*multiplicateur]
          [0.375 Col2*multiplicateur]
          [0.5 Col3*multiplicateur]
          [0.675 Col4*multiplicateur]
          [0.75 Col5*multiplicateur]
          [0.875 Col4*multiplicateur]
          [1.0 Col3*multiplicateur]
                     }
          scale 0.005
             }
           }
#end

#macro Pig_5colors_Wrinkles( multiplicateur, Col1, Col2, Col3, Col4, Col5)
      pigment{
           wrinkles
           color_map{
          [0.0 Col3*multiplicateur]
          [0.125 Col2*multiplicateur]
          [0.25 Col1*multiplicateur]
          [0.375 Col2*multiplicateur]
          [0.5 Col3*multiplicateur]
          [0.675 Col4*multiplicateur]
          [0.75 Col5*multiplicateur]
          [0.875 Col4*multiplicateur]
          [1.0 Col3*multiplicateur]
                    }
         scale 0.005
         }
#end

#declare T_brown2 = T_5var_Wrinkles(1.12  ,brown1_srgb, brown2_srgb,
brown3_srgb, brown4_srgb, brown5_srgb)
#declare GrayPig = Pig_5colors_Wrinkles(1.12, color srgb 0.6, color srgb 0.65,
color srgb 0.7, color srgb 0.75, color srgb 0.8)
#declare BrownPig = Pig_5colors_Wrinkles(1.12  ,brown1_srgb, brown2_srgb,
brown3_srgb, brown4_srgb, brown5_srgb)

#declare FinalGroundPig =
pigment{
    gradient y
    pigment_map{
         [0.0 GrayPig ]
         [0.1 BrownPig ]
               }
}

// simpler substitution for Warren's height_field ground
#declare WholeGround =
plane{y,0
texture{pigment{FinalGroundPig}}
}

WholeGround

#local Norm = < 0, 0, 0>;
#local StartPos = < -12, 100, -11>;
#local FinalPos = trace( WholeGround, StartPos, -y, Norm );
#if( Norm.x != 0 | Norm.y != 0 | Norm.z != 0 )
object{ Pentagram scale PentagramScaleFactor translate FinalPos }
#end


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From: Thomas de Groot
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 20 Jan 2022 11:09:40
Message: <61e98944$1@news.povray.org>
Op 20-1-2022 om 14:20 schreef Kenneth:
> I decided to go through all of the scene's include files-- turning off all of
> the light sources, correcting any out-of-gamut srgb colors to 1.0 max, and
> eliminating every object except the pentagram and the ground.
> 
> And I was still seeing the bright radiosity patches :-(
> 
> So I made my own VERY simplified scene-- posted below-- using just the bare
> necessities of Warren's code plus a few simplifications... and finally
> discovered what I think are the root causes of those bright patches. There are
> THREE reasons, as far as I can tell:
> 
> 1) The sky-sphere object is the primary cause. Comment-out that sphere, and the
> problem patches disappear.
> 
> 2) Radiosity's 'media ON' switch is also a primary problem; turn that OFF and
> the patches disappear.
> 
> 3) The media-pentagram is, I think, halfway embedded in the ground; that seems
> to definitely be adding to the problem, for some reason. Move it even slightly
> upward (like William P. mentioned), and the number of bright patches greatly
> decreases. Not completely, though, as 1) and 2) still produce some patches at
> random.
> 
> I don't know what is going on with rad's 'media on' switch; but the sky-sphere
> problem does not make any sense to me, as its colors are only 0.3 maximum...
> certainly not 'super bright'.
> 
> Maybe others here have some additional clues?
> 
[snip]

I have been very silent on this topic until now. A bit short on time.

I also came across your point (2) so thought it might (at least) be a 
radiosity/media problem. Then I thought that maybe the very thin value 
of the pentagram cylinders might play a role, so I made the cylinder 
radii much thicker while also setting intervals and samples to more 
default values and playing with sample values, but while renders where 
different, the (small) patches remained. I think that (3) might be an 
important issue here, but point (1) is really baffling.

Good work, Kenneth!

-- 
Thomas


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From: Alain Martel
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 20 Jan 2022 12:41:03
Message: <61e99eaf$1@news.povray.org>
Le 2022-01-20 à 08:20, Kenneth a écrit :
> // This light is NOT the cause of the bright radiosity patches.
> light_source{<-2,4,-3 >*1000000 color srgb <0.5,0.5,0.6>*0.75 }
> 

WHY put that light so far away ? Why not use a much closer one, but with 
the parallel attribute ?

When an object or light is situated at a distance in the million units 
range, you can get unexpected behaviour.

Alternative light that will get the exact same result :
light_source{<-2,4,-3 >*1000 color srgb <0.5,0.5,0.6>*0.75 parallel}


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From: Kenneth
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 21 Jan 2022 09:05:00
Message: <web.61eabc54c82cc78e4cef624e6e066e29@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
>
> ...but while renders were
> different, the (small) patches remained. I think that (3) might be an
> important issue here, but point (1) is really baffling.
>
> Good work, Kenneth!
>

Thanks. This has been my most intense 'detective work' in a long time-- and I'm
still thinking about all of it! That sphere problem really bugs me, but I think
I've discovered something interesting about it.

I LIKE a challenge (??) :-O


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From: Kenneth
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 21 Jan 2022 09:55:00
Message: <web.61eac7cac82cc78e4cef624e6e066e29@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:
>
> WHY put that light so far away ? Why not use a much closer one...

I agree. And from more tests, I see that the sky-sphere's gigantic size has a
great deal to do with those super-bright radiosity patches-- which surprised me.

I ran an animation test using my posted 'simplified' code, while changing that
sphere scale from 8000 (which is not *too* large) down to 50. At 8000, the rad
patches are very bright; at 50, they are MUCH less bright. Currently, I don't
know why that should happen-- so I came up with yet another very simple test
scene of my own(!), which I post here. No light_sources in it. It produces the
same weird effect; change the sphere scale to see the difference. (I've also
attached an image example; if you can't see it here, it will nevertheless appear
in the 'image digest'.) Note that all of the scene's color values are purposely
very low.

What this tells me is that any scene with a media object in it, surrounded by
another larger rad-emitting object like that sphere, may show some unexpected
rad/media interactions somewhere, depending on the *scale* of the larger object
and the proximity of the media object to others. It's 'as if' the sphere is
causing brighter radiosity lighting from its colors, the larger it gets. I have
no other guess or explanation at this point. It makes me wonder if certain
radiosity values need tweaking, depending on how large a typical rad-emitting
'sky' sphere is (for example.)

Of course, one of the major reasons for the bright rad patches in all of the
posted scenes here is that the media objects are halfway-embedded in the
'ground'... so there's a proximity effect at work. But I wonder if subtle flaws
might also be occurring in 'typical' media/radiosity scenes that would be
similar to Warren's.

----
#version 3.8;
#declare RAD_ON = 1;
#declare P_start = 64 / image_width;
#declare P_end_final = 4 / image_width;

global_settings{
assumed_gamma 1.0

#if(RAD_ON)
radiosity{ // mostly Warren's settings
pretrace_start P_start
pretrace_end   P_end_final
error_bound 0.2
minimum_reuse 0.15 // Ken
maximum_reuse 0.151 // Ken
nearest_count 9
count 50
recursion_limit 1
always_sample off
//gray_threshold 0.6
brightness 1
adc_bailout 0.01/2
normal on
media on // [If OFF, it ELIMINATES the super-bright radiosity patches.]
         }
#end
}

camera {
  perspective
  location  <15, 70, -140>
  look_at   <0, 0,  -10>
  right     x*image_width/image_height
  angle 40
}

// the large sky-sphere
sphere{0, 1
pigment{rgb .1}
    finish{ambient 0 diffuse 0 emission 1}
    scale 8000 // change to 50
   // hollow on // does not seem to be necessary-- the media objects and
                // rad patches show up anyway
    no_image
}

box{0,1 translate -.5 scale <100,.01,100>
pigment{rgb <.3,.3,1>}
}

merge{ // or union
cylinder{-45*x,45*x,.3}
cylinder{-45*x,45*x,.3 rotate 120*y}
cylinder{-45*x,45*x,.3 rotate 240*y}
hollow
pigment{rgbt 1}
interior{
 media{
  emission .003*<.1,1,.1>
  method 3
  intervals 1
  samples 30
  }
 }
 //translate ... *y
}


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Attachments:
Download 'rad_sphere_scale_test_comp.jpg' (28 KB)

Preview of image 'rad_sphere_scale_test_comp.jpg'
rad_sphere_scale_test_comp.jpg


 

From: Thomas de Groot
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 21 Jan 2022 11:10:04
Message: <61eadadc$1@news.povray.org>
Op 21-1-2022 om 15:52 schreef Kenneth:
> Alain Martel <kua### [at] videotronca> wrote:
>>
>> WHY put that light so far away ? Why not use a much closer one...
> 
> I agree. And from more tests, I see that the sky-sphere's gigantic size has a
> great deal to do with those super-bright radiosity patches-- which surprised me.
> 
> I ran an animation test using my posted 'simplified' code, while changing that
> sphere scale from 8000 (which is not *too* large) down to 50. At 8000, the rad
> patches are very bright; at 50, they are MUCH less bright. Currently, I don't
> know why that should happen-- so I came up with yet another very simple test
> scene of my own(!), which I post here. No light_sources in it. It produces the
> same weird effect; change the sphere scale to see the difference. (I've also
> attached an image example; if you can't see it here, it will nevertheless appear
> in the 'image digest'.) Note that all of the scene's color values are purposely
> very low.
> 
> What this tells me is that any scene with a media object in it, surrounded by
> another larger rad-emitting object like that sphere, may show some unexpected
> rad/media interactions somewhere, depending on the *scale* of the larger object
> and the proximity of the media object to others. It's 'as if' the sphere is
> causing brighter radiosity lighting from its colors, the larger it gets. I have
> no other guess or explanation at this point. It makes me wonder if certain
> radiosity values need tweaking, depending on how large a typical rad-emitting
> 'sky' sphere is (for example.)
> 
> Of course, one of the major reasons for the bright rad patches in all of the
> posted scenes here is that the media objects are halfway-embedded in the
> 'ground'... so there's a proximity effect at work. But I wonder if subtle flaws
> might also be occurring in 'typical' media/radiosity scenes that would be
> similar to Warren's.
> 
> ----
> #version 3.8;
> #declare RAD_ON = 1;
> #declare P_start = 64 / image_width;
> #declare P_end_final = 4 / image_width;
> 
> global_settings{
> assumed_gamma 1.0
> 
> #if(RAD_ON)
> radiosity{ // mostly Warren's settings
> pretrace_start P_start
> pretrace_end   P_end_final
> error_bound 0.2
> minimum_reuse 0.15 // Ken
> maximum_reuse 0.151 // Ken
> nearest_count 9
> count 50
> recursion_limit 1
> always_sample off
> //gray_threshold 0.6
> brightness 1
> adc_bailout 0.01/2
> normal on
> media on // [If OFF, it ELIMINATES the super-bright radiosity patches.]
>           }
> #end
> }
> 
> camera {
>    perspective
>    location  <15, 70, -140>
>    look_at   <0, 0,  -10>
>    right     x*image_width/image_height
>    angle 40
> }
> 
> // the large sky-sphere
> sphere{0, 1
> pigment{rgb .1}
>      finish{ambient 0 diffuse 0 emission 1}
>      scale 8000 // change to 50
>     // hollow on // does not seem to be necessary-- the media objects and
>                  // rad patches show up anyway
>      no_image
> }
> 
> box{0,1 translate -.5 scale <100,.01,100>
> pigment{rgb <.3,.3,1>}
> }
> 
> merge{ // or union
> cylinder{-45*x,45*x,.3}
> cylinder{-45*x,45*x,.3 rotate 120*y}
> cylinder{-45*x,45*x,.3 rotate 240*y}
> hollow
> pigment{rgbt 1}
> interior{
>   media{
>    emission .003*<.1,1,.1>
>    method 3
>    intervals 1
>    samples 30
>    }
>   }
>   //translate ... *y
> }
> 

Is there a reason why the sky sphere has emission 1 ? It is a night 
scene, so I would use emission 0 or emission0.01......

-- 
Thomas


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From: Alain Martel
Subject: Re: weird white stain with beta povray v3.8.0 (not with povrayv3.7.0)
Date: 21 Jan 2022 12:47:57
Message: <61eaf1cd$1@news.povray.org>
Le 2022-01-21 à 11:10, Thomas de Groot a écrit :

> Is there a reason why the sky sphere has emission 1 ? It is a night 
> scene, so I would use emission 0 or emission0.01......
> 

Emission 1 and rgb value of 0.1.
If it was rgb 1, then, a small emission value would be required.


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From: Alain Martel
Subject: Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)
Date: 21 Jan 2022 12:54:13
Message: <61eaf345$1@news.povray.org>
Le 2022-01-21 à 09:52, Kenneth a écrit :
> // the large sky-sphere
> sphere{0, 1
> pigment{rgb .1}
>      finish{ambient 0 diffuse 0 emission 1}
>      scale 8000 // change to 50
>     // hollow on // does not seem to be necessary-- the media objects and
>                  // rad patches show up anyway
>      no_image
> }

Have you tried to replace that large sphere with a sky_sphere ? Or even 
a simple background statement if the pigment is solid ?
Some options :

background{ rgb 0.1 }

sky_sphere{
	pigment{ rgb 0.1 }
   }

sky_sphere{
  pigment{plnar{
	[0 rgb 0.1]
	[1 rgb 0]
	}
    }


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