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From: Mike Horvath
Subject: Lightsys
Date: 23 Feb 2018 04:56:24
Message: <5a8f9ef8$1@news.povray.org>
Are there any old scenes or renders that I can use to compare behavior 
in old and current versions of POV-Ray? By default, using 1 lumens the 
daylight scenes seem dim and washed out. I have to pump up the lumens to 
2 or 3 to get nice daylight colors and brightness. Thanks.


Mike


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From: Mike Horvath
Subject: Re: Lightsys
Date: 23 Feb 2018 05:00:05
Message: <5a8f9fd5$1@news.povray.org>
On 2/22/2018 11:56 PM, Mike Horvath wrote:
> Are there any old scenes or renders that I can use to compare behavior 
> in old and current versions of POV-Ray? By default, using 1 lumens the 
> daylight scenes seem dim and washed out. I have to pump up the lumens to 
> 2 or 3 to get nice daylight colors and brightness. Thanks.
> 
> 
> Mike

This is a render with 2 lumens:

https://i.imgur.com/wHmo76S.jpg

This is a render with 3 lumens:

https://i.imgur.com/Q50eHAz.jpg

Here is the code I am using.



// -------------------------------------------------------------
// Nonstandard includes

#include "CIE.inc"					// 
http://www.ignorancia.org/en/index.php?page=Lightsys
#include "lightsys.inc"				// 
http://www.ignorancia.org/en/index.php?page=Lightsys
#include "lightsys_constants.inc"	// 
http://www.ignorancia.org/en/index.php?page=Lightsys


// -------------------------------------------------------------
// Lights
// Sun is not at realistic distance and is not an area light like it 
should be.
// Could use "sunpos.inc" here too to determine a correct position and 
angle.

#declare light_source_lumens	= 3;				// float
#declare light_source_temp		= Daylight(6100);	// float
#declare light_source_color		= 
Light_Color(light_source_temp,light_source_lumens);	// float
#declare light_source_location	= vrotate(<0,0,-1000000000>, 
<-060,-060,+000>);			// needs to be far enough above the clouds to cast 
shadows

light_source
{
	light_source_location
	srgb light_source_color
	parallel
	point_at <0,0,0>
}


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From: Alain
Subject: Re: Lightsys
Date: 23 Feb 2018 13:10:01
Message: <5a9012a9$1@news.povray.org>
Le 18-02-23 à 00:00, Mike Horvath a écrit :
> On 2/22/2018 11:56 PM, Mike Horvath wrote:
>> Are there any old scenes or renders that I can use to compare behavior 
>> in old and current versions of POV-Ray? By default, using 1 lumens the 
>> daylight scenes seem dim and washed out. I have to pump up the lumens 
>> to 2 or 3 to get nice daylight colors and brightness. Thanks.
>>
>>
>> Mike
> 
> This is a render with 2 lumens:
> 
> https://i.imgur.com/wHmo76S.jpg
> 
> This is a render with 3 lumens:
> 
> https://i.imgur.com/Q50eHAz.jpg
> 
> Here is the code I am using.
> 
> 
> 
> // -------------------------------------------------------------
> // Nonstandard includes
> 
> #include "CIE.inc"                    // 
> http://www.ignorancia.org/en/index.php?page=Lightsys
> #include "lightsys.inc"                // 
> http://www.ignorancia.org/en/index.php?page=Lightsys
> #include "lightsys_constants.inc"    // 
> http://www.ignorancia.org/en/index.php?page=Lightsys
> 
> 
> // -------------------------------------------------------------
> // Lights
> // Sun is not at realistic distance and is not an area light like it 
> should be.
> // Could use "sunpos.inc" here too to determine a correct position and 
> angle.
> 
> #declare light_source_lumens    = 3;                // float
> #declare light_source_temp        = Daylight(6100);    // float
> #declare light_source_color        = 
> Light_Color(light_source_temp,light_source_lumens);    // float
> #declare light_source_location    = vrotate(<0,0,-1000000000>, 
> <-060,-060,+000>);            // needs to be far enough above the clouds 
> to cast shadows
> 
> light_source
> {
>      light_source_location
>      srgb light_source_color
>      parallel
>      point_at <0,0,0>
> }

lightsys assume that you are using a linear colour space : Use rgb, not 
srgb. Also, use assumed_gamma 1.

If you use srgb, then light components that are larger than 1 will get 
their value reduced, potentially making your light somewhat dimer.


Alain


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From: Alain
Subject: Re: Lightsys
Date: 23 Feb 2018 13:17:44
Message: <5a901478$1@news.povray.org>
Le 18-02-23 à 00:00, Mike Horvath a écrit :
> On 2/22/2018 11:56 PM, Mike Horvath wrote:
>> Are there any old scenes or renders that I can use to compare behavior 
>> in old and current versions of POV-Ray? By default, using 1 lumens the 
>> daylight scenes seem dim and washed out. I have to pump up the lumens 
>> to 2 or 3 to get nice daylight colors and brightness. Thanks.
>>
>>
>> Mike
> 
> This is a render with 2 lumens:
> 
> https://i.imgur.com/wHmo76S.jpg
> 
> This is a render with 3 lumens:
> 
> https://i.imgur.com/Q50eHAz.jpg
> 
> Here is the code I am using.
> 
> 
> 
> // -------------------------------------------------------------
> // Nonstandard includes
> 
> #include "CIE.inc"                    // 
> http://www.ignorancia.org/en/index.php?page=Lightsys
> #include "lightsys.inc"                // 
> http://www.ignorancia.org/en/index.php?page=Lightsys
> #include "lightsys_constants.inc"    // 
> http://www.ignorancia.org/en/index.php?page=Lightsys
> 
> 
> // -------------------------------------------------------------
> // Lights
> // Sun is not at realistic distance and is not an area light like it 
> should be.
> // Could use "sunpos.inc" here too to determine a correct position and 
> angle.
> 
> #declare light_source_lumens    = 3;                // float
> #declare light_source_temp        = Daylight(6100);    // float
> #declare light_source_color        = 
> Light_Color(light_source_temp,light_source_lumens);    // float
> #declare light_source_location    = vrotate(<0,0,-1000000000>, 
> <-060,-060,+000>);            // needs to be far enough above the clouds 
> to cast shadows
> 
> light_source
> {
>      light_source_location
>      srgb light_source_color
>      parallel
>      point_at <0,0,0>
> }

The 3 lumen looks a little to bright.
Can you post the 1 lumen image?

Also, the sun position is not the same for the two images. It mover by 
around 40°.


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From: Mike Horvath
Subject: Re: Lightsys
Date: 24 Feb 2018 16:06:33
Message: <5a918d89$1@news.povray.org>
On 2/23/2018 8:18 AM, Alain wrote:
> The 3 lumen looks a little to bright.
> Can you post the 1 lumen image?
> 
> Also, the sun position is not the same for the two images. It mover by 
> around 40°.

Here it is with RGB instead of SRGB, and 1 lumens.

https://i.imgur.com/AcGBbla.jpg

As you can see, it is pretty dim and lifeless.


Mike


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From: Alain
Subject: Re: Lightsys
Date: 24 Feb 2018 17:22:47
Message: <5a919f67@news.povray.org>
Le 18-02-24 à 11:07, Mike Horvath a écrit :
> On 2/23/2018 8:18 AM, Alain wrote:
>> The 3 lumen looks a little to bright.
>> Can you post the 1 lumen image?
>>
>> Also, the sun position is not the same for the two images. It mover by 
>> around 40°.
> 
> Here it is with RGB instead of SRGB, and 1 lumens.
> 
> https://i.imgur.com/AcGBbla.jpg
> 
> As you can see, it is pretty dim and lifeless.
> 
> 
> Mike

Slightly dimmer, not prety dim, than the 2 lumens but not lifeless on my 
monitor. Maybe your monitor is set to dim...
Definitively better than the 3 lumens version.

Set assumed_gamma 1
When using lightsys, always use RGB for the lights. lightsys is made to 
return values in the rgb colour space, not the srgb one. You may use 
srgb for the textures.


Alain


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From: Thomas de Groot
Subject: Re: Lightsys
Date: 25 Feb 2018 07:53:27
Message: <5a926b77@news.povray.org>
On 24-2-2018 17:07, Mike Horvath wrote:
> On 2/23/2018 8:18 AM, Alain wrote:
>> The 3 lumen looks a little to bright.
>> Can you post the 1 lumen image?
>>
>> Also, the sun position is not the same for the two images. It mover by 
>> around 40°.
> 
> Here it is with RGB instead of SRGB, and 1 lumens.
> 
> https://i.imgur.com/AcGBbla.jpg
> 
> As you can see, it is pretty dim and lifeless.
> 

On my screen it looks right.

I often use CIE.inc myself, maybe in a little different way than you do. 
This is an example of how I define my sunlight in a scene:

//start code -----------------------------------
#include "CIE.inc"
#if (Fog)
   #local Intensity    = 5;
#else
   #local Intensity    = 3;
#end
//Sun's temperature (Kelvin): 2800=red; 7500=blue white
#declare SunColor     = Blackbody(6500)*Intensity;
#declare SunPosition  = <0, 0, -2>*10e4;
#declare SunDis       = vlength(SunPosition)*2/215;
#declare Sun_alt      = 60;
#declare Sun_azm      = -115;

#if (Area)
   #debug "\nUsing an area_light for the Sun.\n"
   light_source{
     <0, 0, 0>
     color SunColor
     area_light
     SunDis*x, SunDis*z, // lights spread out (x * z)
     4, 4                // total lights in grid (4x*4z = 16 lights)
     adaptive 1          // 0,1,2,3...
     area_illumination on  // full area diffuse and specular
     jitter              // adds random softening of light
     circular            // make the shape of the light circular
     orient              // orient light
     translate SunPosition
     rotate Sun_alt*x
     rotate Sun_azm*y
     parallel
     point_at <0, 0, 0>
     media_interaction on
     media_attenuation off
   }
#else
   light_source {
     <0, 0, 0>
     color rgb SunColor
     translate SunPosition
     rotate Sun_alt*x
     rotate Sun_azm*y
     parallel
     point_at <0, 0, 0>
     media_interaction on
     media_attenuation off
   }
#end
//end code -----------------------------------


-- 
Thomas


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From: Alain
Subject: Re: Lightsys
Date: 26 Feb 2018 00:02:50
Message: <5a934eaa@news.povray.org>
Le 18-02-25 à 02:53, Thomas de Groot a écrit :
> On 24-2-2018 17:07, Mike Horvath wrote:
>> On 2/23/2018 8:18 AM, Alain wrote:
>>> The 3 lumen looks a little to bright.
>>> Can you post the 1 lumen image?
>>>
>>> Also, the sun position is not the same for the two images. It mover 
>>> by around 40°.
>>
>> Here it is with RGB instead of SRGB, and 1 lumens.
>>
>> https://i.imgur.com/AcGBbla.jpg
>>
>> As you can see, it is pretty dim and lifeless.
>>
> 
> On my screen it looks right.
> 
> I often use CIE.inc myself, maybe in a little different way than you do. 
> This is an example of how I define my sunlight in a scene:
> 
> //start code -----------------------------------
> #include "CIE.inc"
> #if (Fog)
>    #local Intensity    = 5;
> #else
>    #local Intensity    = 3;
> #end
> //Sun's temperature (Kelvin): 2800=red; 7500=blue white
> #declare SunColor     = Blackbody(6500)*Intensity;
> #declare SunPosition  = <0, 0, -2>*10e4;
> #declare SunDis       = vlength(SunPosition)*2/215;
> #declare Sun_alt      = 60;
> #declare Sun_azm      = -115;
> 
> #if (Area)
>    #debug "\nUsing an area_light for the Sun.\n"
>    light_source{
>      <0, 0, 0>
>      color SunColor
>      area_light
>      SunDis*x, SunDis*z, // lights spread out (x * z)

A better, more descriptive, name would be "SunDiam"

>      4, 4                // total lights in grid (4x*4z = 16
lights)

This will actually use a 5 by 5 array...

>      adaptive 1          // 0,1,2,3...

...and start with a 3 by 3 one.
With adaptive, you can use a much larger value, like 17 or 33 without 
increasing the render time much.
adaptive 0 DON'T turn the feature off, but start with a 2 by 2 array.

>      area_illumination on  // full area diffuse and specular
>      jitter              // adds random softening of light

Makes the penumbra grainy if using a sparse array.

>      circular            // make the shape of the light circular
>      orient              // orient light
>      translate SunPosition
>      rotate Sun_alt*x
>      rotate Sun_azm*y
>      parallel
>      point_at <0, 0, 0>
>      media_interaction on
>      media_attenuation off
>    }
> #else
>    light_source {
>      <0, 0, 0>
>      color rgb SunColor
>      translate SunPosition
>      rotate Sun_alt*x
>      rotate Sun_azm*y
>      parallel
>      point_at <0, 0, 0>
>      media_interaction on
>      media_attenuation off
>    }
> #end
> //end code -----------------------------------
> 
> 

Using adaptive, you need larger arrays to get all the benefit. Some 
suggested sizes in relation with the adaptive steps values :
adaptive 0 (0 initial subdivisions)  at least 5 by 5 (2 steps)
adaptive 1 (1 initial subdivisions)  at least 9 by 9 (3 steps)
adaptive 2 (2 initial subdivisions)  at least 17 by 17 (4 steps)
adaptive 3 (3 initial subdivisions)  at least 33 by 33 (5 steps)

You can always use larger arrays to get smoother results.


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From: Thomas de Groot
Subject: Re: Lightsys
Date: 26 Feb 2018 07:43:55
Message: <5a93babb$1@news.povray.org>
On 26-2-2018 1:03, Alain wrote:
> Le 18-02-25 à 02:53, Thomas de Groot a écrit :
>> On 24-2-2018 17:07, Mike Horvath wrote:
>>> On 2/23/2018 8:18 AM, Alain wrote:
>>>> The 3 lumen looks a little to bright.
>>>> Can you post the 1 lumen image?
>>>>
>>>> Also, the sun position is not the same for the two images. It mover 
>>>> by around 40°.
>>>
>>> Here it is with RGB instead of SRGB, and 1 lumens.
>>>
>>> https://i.imgur.com/AcGBbla.jpg
>>>
>>> As you can see, it is pretty dim and lifeless.
>>>
>>
>> On my screen it looks right.
>>
>> I often use CIE.inc myself, maybe in a little different way than you 
>> do. This is an example of how I define my sunlight in a scene:
>>
>> //start code -----------------------------------
>> #include "CIE.inc"
>> #if (Fog)
>>    #local Intensity    = 5;
>> #else
>>    #local Intensity    = 3;
>> #end
>> //Sun's temperature (Kelvin): 2800=red; 7500=blue white
>> #declare SunColor     = Blackbody(6500)*Intensity;
>> #declare SunPosition  = <0, 0, -2>*10e4;
>> #declare SunDis       = vlength(SunPosition)*2/215;
>> #declare Sun_alt      = 60;
>> #declare Sun_azm      = -115;
>>
>> #if (Area)
>>    #debug "\nUsing an area_light for the Sun.\n"
>>    light_source{
>>      <0, 0, 0>
>>      color SunColor
>>      area_light
>>      SunDis*x, SunDis*z, // lights spread out (x * z)
> 
> A better, more descriptive, name would be "SunDiam"
> 
>>      4, 4                // total lights in grid (4x*4z = 16
lights)
> 
> This will actually use a 5 by 5 array...
> 
>>      adaptive 1          // 0,1,2,3...
> 
> ...and start with a 3 by 3 one.
> With adaptive, you can use a much larger value, like 17 or 33 without 
> increasing the render time much.
> adaptive 0 DON'T turn the feature off, but start with a 2 by 2 array.
> 
>>      area_illumination on  // full area diffuse and specular
>>      jitter              // adds random softening of light
> 
> Makes the penumbra grainy if using a sparse array.
> 
>>      circular            // make the shape of the light circular
>>      orient              // orient light
>>      translate SunPosition
>>      rotate Sun_alt*x
>>      rotate Sun_azm*y
>>      parallel
>>      point_at <0, 0, 0>
>>      media_interaction on
>>      media_attenuation off
>>    }
>> #else
>>    light_source {
>>      <0, 0, 0>
>>      color rgb SunColor
>>      translate SunPosition
>>      rotate Sun_alt*x
>>      rotate Sun_azm*y
>>      parallel
>>      point_at <0, 0, 0>
>>      media_interaction on
>>      media_attenuation off
>>    }
>> #end
>> //end code -----------------------------------
>>
>>
> 
> Using adaptive, you need larger arrays to get all the benefit. Some 
> suggested sizes in relation with the adaptive steps values :
> adaptive 0 (0 initial subdivisions)  at least 5 by 5 (2 steps)
> adaptive 1 (1 initial subdivisions)  at least 9 by 9 (3 steps)
> adaptive 2 (2 initial subdivisions)  at least 17 by 17 (4 steps)
> adaptive 3 (3 initial subdivisions)  at least 33 by 33 (5 steps)
> 
> You can always use larger arrays to get smoother results.

Thanks Alain, well spotted indeed. I always unthinkingly use the set up 
as is. ;-)

-- 
Thomas


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From: Mike Horvath
Subject: Re: Lightsys
Date: 26 Feb 2018 22:51:08
Message: <5a948f5c$1@news.povray.org>
On 2/24/2018 12:23 PM, Alain wrote:
> Le 18-02-24 à 11:07, Mike Horvath a écrit :
>> On 2/23/2018 8:18 AM, Alain wrote:
>>> The 3 lumen looks a little to bright.
>>> Can you post the 1 lumen image?
>>>
>>> Also, the sun position is not the same for the two images. It mover 
>>> by around 40°.
>>
>> Here it is with RGB instead of SRGB, and 1 lumens.
>>
>> https://i.imgur.com/AcGBbla.jpg
>>
>> As you can see, it is pretty dim and lifeless.
>>
>>
>> Mike
> 
> Slightly dimmer, not prety dim, than the 2 lumens but not lifeless on my 
> monitor. Maybe your monitor is set to dim...
> Definitively better than the 3 lumens version.
> 
> Set assumed_gamma 1
> When using lightsys, always use RGB for the lights. lightsys is made to 
> return values in the rgb colour space, not the srgb one. You may use 
> srgb for the textures.
> 
> 
> Alain

My monitor is set to "SRGB". Dunno what it should be set to.


Mike


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