While finding new and better ways to make media explosions, I ran into a 
serious in that scattering media objects cannot be illuminated by 
shadowless lights or by lights used in a light_group.  While I know that 
shadowless lights do some funny things, I tend to think that getting 
ignored by media is a bit much, and that the light_group problem is a 
blatant bug.

Example scene:
/*
  When rendered as is, the media is grey.  When rendered with light group
  and/or with shadowless enabled, the media will be black (unlit).
*/
camera {location z*3 look_at 0} plane {z,-5 pigment {checker rgb 1 rgb .3} 
finish {ambient 1 diffuse 0}}

//light_group {

sphere {0,1 hollow pigment {rgbf 1} interior {
    media {
        scattering {1, 8}
        density {spherical color_map {[0 rgb 0][1 rgb 1]}}
}}}

light_source {<1e6,0,1e6> 1 /*shadowless*/}

//} // end brace for light_group

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In article <Xns### [at] 204213191226> , che### [at] sympaticoca
(Coridon Henshaw) wrote:

> While finding new and better ways to make media explosions, I ran into a
> serious in that scattering media objects cannot be illuminated by
> shadowless lights or by lights used in a light_group.  While I know that
> shadowless lights do some funny things, I tend to think that getting
> ignored by media is a bit much, and that the light_group problem is a
> blatant bug.

Could you check if this is or isn't the same as

From: "Ari-Matti Leppanen" <ari### [at] tutfi>
Newsgroups: povray.beta-test
Subject: Light_groups and Media
Date: Sun, 10 Feb 2002 11:31:11 +0200
Message-ID: <3c663dd3$1@news.povray.org>
Xref: news.povray.org povray.beta-test:4552


    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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Isn't the illumination of scattering media technically a shadow test?
Thus a shadowless light...

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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I don't think it's a good idea to have a flag which implies other flags. Why should
the shadowless flag imply media_interaction off? I think each flag should be specific
(that's why I'd personally love a no_radiosity and a no_specular flag).

Or, at least, this behaviour should be documented.

--
Jonathan.

"Warp" <war### [at] tagpovrayorg> ha scritto nel messaggio
news:3c835c4b@news.povray.org...
>   Isn't the illumination of scattering media technically a shadow test?
> Thus a shadowless light...
>
> --
> #macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
> N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
> N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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On Mon, 4 Mar 2002 19:15:21 +0100, "JRG" <jrg### [at] hotmailcom> wrote:

>I don't think it's a good idea to have a flag which implies other flags. Why should
>the shadowless flag imply media_interaction off? I think each flag should be specific
>(that's why I'd personally love a no_radiosity and a no_specular flag).

Shadowless implies not casting shadows in scattering media. It should
not imply media_interraction off. If it does, it sounds like a bug.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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"Thorsten Froehlich" <tho### [at] trfde> wrote in
news:3c832a40$1@news.povray.org: 

> In article <Xns### [at] 204213191226> ,
> che### [at] sympaticoca (Coridon Henshaw) wrote:
> 
>> While finding new and better ways to make media explosions, I ran into
>> a serious in that scattering media objects cannot be illuminated by
>> shadowless lights or by lights used in a light_group.  While I know
>> that shadowless lights do some funny things, I tend to think that
>> getting ignored by media is a bit much, and that the light_group
>> problem is a blatant bug. 
 
> Could you check if this is or isn't the same as

The issue with media and light groups appears to be the same as
<3c663dd3$1@news.povray.org>.  While looking at the other report, I also 
noticed that global_lights defaults to 'on' and can't be switched off for 
media objects in a light_group.

The problem with shadowless is separate.

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Peter Popov <pet### [at] vipbg> wrote in
news:bii78ugisrrqq0labhk54k2b2pl52cacmg@4ax.com: 

> On Mon, 4 Mar 2002 19:15:21 +0100, "JRG" <jrg### [at] hotmailcom> wrote:
> 
>>I don't think it's a good idea to have a flag which implies other
>>flags. Why should the shadowless flag imply media_interaction off? I
>>think each flag should be specific (that's why I'd personally love a
>>no_radiosity and a no_specular flag). 

> Shadowless implies not casting shadows in scattering media. It should
> not imply media_interraction off. If it does, it sounds like a bug.

As far as the Megapov lighting code is concerned, shadowless doesn't set 
media_interaction=off per say but has pretty much the same effect due to 
the way media illumination is calculated.

At first glance, most of the fix is to modify test_shadow() in lighting.c 
such that shadow tests are performed with shadowless lights (remove 
(Light->Projected_Through_Object != NULL) from the shadow test conditional) 
and then to adapt block_point_light() et el so that when handling 
shadowless lights, filter_shadow_ray() is only called when the shadowed 
object contains a media.  Unless I've overlooked something major, both of 
these tasks should be relatively straight forward.

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On 4 Mar 2002 15:56:08 -0500, che### [at] sympaticoca (Coridon Henshaw)
wrote:

>At first glance, most of the fix is to modify test_shadow() in lighting.c 
>such that shadow tests are performed with shadowless lights (remove 
>(Light->Projected_Through_Object != NULL) from the shadow test conditional) 
>and then to adapt block_point_light() et el so that when handling 
>shadowless lights, filter_shadow_ray() is only called when the shadowed 
>object contains a media.  Unless I've overlooked something major, both of 
>these tasks should be relatively straight forward.

So basically what you're suggesting that objects will not cast shadows
from shadowless lights anywhere except in scattering media? Doesn't it
look a bit inconsistent?


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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> So basically what you're suggesting that objects will not cast shadows
> from shadowless lights anywhere except in scattering media? Doesn't it
> look a bit inconsistent?

Sorry for putting words in someone's mouth, but I believe he's suggesting
that shadowless lights don't illuminate scattering media at all.

- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]

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On Tue, 5 Mar 2002 02:05:41 -0500, "Slime" <noo### [at] hotmailcom>
wrote:

>Sorry for putting words in someone's mouth, but I believe he's suggesting
>that shadowless lights don't illuminate scattering media at all.

Which would also be inconsistent.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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