POV-Ray : Newsgroups : povray.newusers : Colored shadows Server Time: 12 Dec 2018 22:19:31 GMT
  Colored shadows (Message 1 to 5 of 5)  
From: Mr
Subject: Colored shadows
Date: 1 Feb 2017 13:50:01
Message: <web.5891e757b222159a16086ed00@news.povray.org>
Hi,
I know this is not a realistic feature.
Is there a way to specify that all shadows cast by one light are colored by some
tint? (I'm not talking of the highlight color, but rather separate tint of the
shadows and on a per light basis.)


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From: Alain
Subject: Re: Colored shadows
Date: 1 Feb 2017 21:25:37
Message: <58925251$1@news.povray.org>
Le 17-02-01 à 08:49, Mr a écrit :
> Hi,
> I know this is not a realistic feature.
> Is there a way to specify that all shadows cast by one light are colored by some
> tint? (I'm not talking of the highlight color, but rather separate tint of the
> shadows and on a per light basis.)
>
>

Possible but cumbersome. It involve using projected_through lights 
associated with your base light(s).

It should work as follow:
Declare all the objects that are to have coloured shadows in some large 
unions.
Place that, or those, union in your scene.
Place all of your lights.
Place copies of all the lights that are to cast coloured shadows. Those 
copies have the colour that you want the shadows to have. They also have 
the projected_through attribute using your large union.

Think of projected_through as some kind of «anti-shadow» lights. THey 
shine in areas that would otherwise be in shadow and don't shine in 
areas that would be lighted using a normal light_source.
It works well with area_light and parallel.
Using spot_light is pointless.
In my tests, it don't like photons. You need to set the 
projected_through object as photons{pass_thgough} or it won't produce 
any photons.

It should be interesting using transparent objects as projected_through 
object. Would an object with pigment{rgbf<0,1,0,1>} gives magenta 
illumination?


Alain


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From: clipka
Subject: Re: Colored shadows
Date: 2 Feb 2017 12:48:56
Message: <58932ab8$1@news.povray.org>
Am 01.02.2017 um 14:49 schrieb Mr:
> Hi,
> I know this is not a realistic feature.
> Is there a way to specify that all shadows cast by one light are colored by some
> tint? (I'm not talking of the highlight color, but rather separate tint of the
> shadows and on a per light basis.)

Since a shadow by definition is the complete /absence/ of any influence
whatsoever from a specific light source, that's not possible.

However, as Alain mentioned already, POV-Ray's `projected_through`
mechanism /may/ be a useful tool for what you are trying to achieve,
depending on your exact intentions.


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From: scott
Subject: Re: Colored shadows
Date: 2 Feb 2017 13:01:42
Message: <58932db6$1@news.povray.org>
> I know this is not a realistic feature.
> Is there a way to specify that all shadows cast by one light are colored by some
> tint? (I'm not talking of the highlight color, but rather separate tint of the
> shadows and on a per light basis.)

You could try replacing your existing light_source with:

light_source{ color shadow_colour shadowless}
light_source{ color (X-shadow_colour) }

Where X is the original colour of your light, and shadow_colour is the 
colour you want your shadows to be illuminated with.

eg:

light_source{<-10,25,-25> color rgb <0.4,0.0,0.0> shadowless}
light_source{<-10,25,-25> color rgb <0.6,1.0,1.0>}

Will give red tinted shadows, but still give white light for bits not in 
shadow.


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From: clipka
Subject: Re: Colored shadows
Date: 2 Feb 2017 14:33:51
Message: <5893434f$1@news.povray.org>
Am 02.02.2017 um 14:01 schrieb scott:
>> I know this is not a realistic feature.
>> Is there a way to specify that all shadows cast by one light are
>> colored by some
>> tint? (I'm not talking of the highlight color, but rather separate
>> tint of the
>> shadows and on a per light basis.)
> 
> You could try replacing your existing light_source with:
> 
> light_source{ color shadow_colour shadowless}
> light_source{ color (X-shadow_colour) }
> 
> Where X is the original colour of your light, and shadow_colour is the
> colour you want your shadows to be illuminated with.

Looks legit; smart idea!


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