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From: Ansgar
Subject: Problem with "no_image" and transparency?
Date: 24 Sep 2007 23:45:01
Message: <web.46f84a9cd032f3c7cb86afba0@news.povray.org>
I have a kinda weird problem with the newest beta. I hope I can explain it
in a not too confusing way.

Around my scene, I have a large sphere with the parameters
no_image
no_shadow
inverse
It serves as a kind of reflection or environment map, as shiny surfaces in
my scene will reflect this sphere while the thing itself is invisible.

With the latest beta, weird things happen to object that have a transparent
or semi-transparent surface. While the exterior surface is correctly made
transparent, the then-visible interior is not... it shows the texture of
that sphere instead.
I tried defining an "interior_texture" for those objects, setting them to
full transparency, but that didn't change a thing.

I'd like to know if that is a bug in the new beta or just some new way of
interpreting textures... in the latter case, what do I have to change?

Thx,
Ansgar


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From: Warp
Subject: Re: Problem with "no_image" and transparency?
Date: 25 Sep 2007 06:58:19
Message: <46f8b18a@news.povray.org>
Ansgar <Tem### [at] gmxde> wrote:
> no_image
> no_shadow
> inverse

> With the latest beta, weird things happen to object that have a transparent
> or semi-transparent surface. While the exterior surface is correctly made
> transparent, the then-visible interior is not... it shows the texture of
> that sphere instead.

  Are you sure this doesn't happen with POV-Ray 3.6 too? Because I can't
see anything logically wrong with that behavior according to the settings
you have specified. ('no_image' means that the object is ignored for rays
shot directly from the camera, ie. the first recursion rays, but when a
ray goes through an object it's not a first-recursion ray anymore.)

-- 
                                                          - Warp


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From: Ansgar
Subject: Re: Problem with "no_image" and transparency?
Date: 25 Sep 2007 08:15:00
Message: <web.46f8c270aff96f2fcb86afba0@news.povray.org>
It does not happen in 3.6.
Transparent or semi-transparent parts let the background color of the scene
show through, as it should be.


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From: Ansgar
Subject: Re: Problem with "no_image" and transparency?
Date: 25 Sep 2007 09:10:00
Message: <web.46f8d032aff96f2fcb86afba0@news.povray.org>
I just went through the POV-Ray help and found this in the section about
"no_image".

"When no_image is used, the object will not be seen by the camera, either
directly or through transparent/refractive objects. However, it will still
cast shadows, and show up in reflections (unless no_reflection and/or
no_shadow is used also)."

There you go. The object is not supposed to be seen through
transparent/refractive objects.


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From: Warp
Subject: Re: Problem with "no_image" and transparency?
Date: 25 Sep 2007 10:55:34
Message: <46f8e926@news.povray.org>
Ansgar <Tem### [at] gmxde> wrote:
> There you go. The object is not supposed to be seen through
> transparent/refractive objects.

  Then it's probably a bug in 3.7.

-- 
                                                          - Warp


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From: Chris Cason
Subject: Re: Problem with "no_image" and transparency?
Date: 25 Sep 2007 23:17:43
Message: <46f99717@news.povray.org>
Ansgar wrote:
> I just went through the POV-Ray help and found this in the section about
> "no_image".
> 
> "When no_image is used, the object will not be seen by the camera, either
> directly or through transparent/refractive objects. However, it will still
> cast shadows, and show up in reflections (unless no_reflection and/or
> no_shadow is used also)."
> 
> There you go. The object is not supposed to be seen through
> transparent/refractive objects.

Please post a minimal sample scene for us to work with.

thanks,

-- Chris


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From: Alain
Subject: Re: Problem with "no_image" and transparency?
Date: 26 Sep 2007 13:17:46
Message: <46fa5bfa$1@news.povray.org>
Chris Cason nous apporta ses lumieres en ce 2007/09/25 19:17:
> Ansgar wrote:
>> I just went through the POV-Ray help and found this in the section about
>> "no_image".
>>
>> "When no_image is used, the object will not be seen by the camera, either
>> directly or through transparent/refractive objects. However, it will still
>> cast shadows, and show up in reflections (unless no_reflection and/or
>> no_shadow is used also)."
>>
>> There you go. The object is not supposed to be seen through
>> transparent/refractive objects.
> 
> Please post a minimal sample scene for us to work with.
> 
> thanks,
> 
> -- Chris
As minimal as you can:

plane{z, 15 pigment{checker}finish{ambient 1} no_image}
sphere{<0,0,3>,1 pigment{rgbt 1}}

It should be all black but you see the checker pigment through the sphere.

-- 
Alain
-------------------------------------------------
Documentation; The worst part of programming.


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From: Le Forgeron
Subject: Re: Problem with "no_image" and transparency?
Date: 26 Sep 2007 15:41:42
Message: <46fa7db6@news.povray.org>
Le 26.09.2007 15:17, Alain nous fit lire :

> As minimal as you can:
> 
> plane{z, 15 pigment{checker}finish{ambient 1} no_image}
> sphere{<0,0,3>,1 pigment{rgbt 1}}
> 
> It should be all black but you see the checker pigment through the sphere.
> 
does it mean we need no_transmission and no_refraction also ?

-- 
The superior man understands what is right;
the inferior man understands what will sell.
-- Confucius


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From: Alain
Subject: Re: Problem with "no_image" and transparency?
Date: 26 Sep 2007 18:56:50
Message: <46faab72$1@news.povray.org>
Le Forgeron nous apporta ses lumieres en ce 2007/09/26 11:41:
> Le 26.09.2007 15:17, Alain nous fit lire :
> 
>> As minimal as you can:
>>
>> plane{z, 15 pigment{checker}finish{ambient 1} no_image}
>> sphere{<0,0,3>,1 pigment{rgbt 1}}
>>
>> It should be all black but you see the checker pigment through the sphere.
>>
> does it mean we need no_transmission and no_refraction also ?
> 
No. Just make no_image work coherently between versions, and according to the 
documentations.

An object with no_image is normaly invisible, but still cast shadows and show in 
reflections.

An object with no_reflection is visible, cast shadow, but don't show in reflections.

An object with no_shadow is visible normaly and in reflections but don't cast 
any shadow.

-- 
Alain
-------------------------------------------------
WARNING: The consumption of alcohol is a major factor in dancing like a retard.


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From: Nicolas Alvarez
Subject: Re: Problem with "no_image" and transparency?
Date: 29 Sep 2007 20:55:05
Message: <46febba9@news.povray.org>
Alain escribió:
> Le Forgeron nous apporta ses lumieres en ce 2007/09/26 11:41:
>> Le 26.09.2007 15:17, Alain nous fit lire :
>> does it mean we need no_transmission and no_refraction also ?
>>
 >
> No. Just make no_image work coherently between versions, and according 
> to the documentations.
> 

Why not? We could have no_image work coherently between versions and new 
no_transmission and no_refraction keywords too ;-)


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