POV-Ray : Newsgroups : povray.general : Looks_like object with Normal = Strange things Server Time
12 Aug 2024 19:34:44 EDT (-0400)
  Looks_like object with Normal = Strange things (Message 1 to 3 of 3)  
From: Ruben Soto
Subject: Looks_like object with Normal = Strange things
Date: 30 Jan 1999 10:59:25
Message: <36B32C74.7557@jet.es>
Hi, I have noticed that when you have a Look_like inside a light
source, and you apply it to an object that has a normal modifier, the
object can be seen even though there is no other light and its ambient
value is set to 0. According to the manuals, this object should be dark.


as expected. Any ideas? Is this a bug, an undocumented feature, or too
many hours raytracing without taking a break? ;-)

  Best regards,

  Ruben


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From: Bob Hughes
Subject: Re: Looks_like object with Normal = Strange things
Date: 1 Feb 1999 16:24:56
Message: <36B61B90.DAEB47F0@aol.com>
Don't know what you mean about the DOC saying a 'looks_like{OBJECT}'
should only be "dark".
It is always 'shadowless', but usually people want such a thing to show
up, such as a (not totally transparent) light bulb. This way it is
visible and casts no shadow itself, only the 'light_source' does.
Adding a 'normal' and scaling it very small in relation to overall
OBJECT size can help to make a semi-transparent object more visible.
If you have to have an invisible looks_like{OBJECT}, then turn down the
normal value or don't use one at all.
Hope this is what you are saying, that you think the looks_like remains
invisible and it isn't doing so for what you are trying.


Ruben Soto wrote:
> 
> Hi, I have noticed that when you have a Look_like inside a light
> source, and you apply it to an object that has a normal modifier, the
> object can be seen even though there is no other light and its ambient
> value is set to 0. According to the manuals, this object should be dark.


> as expected. Any ideas? Is this a bug, an undocumented feature, or too
> many hours raytracing without taking a break? ;-)
> 
>   Best regards,
> 
>   Ruben

-- 
 omniVERSE: beyond the universe
  http://members.aol.com/inversez/POVring.htm
=Bob


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From: axixlab
Subject: Re: Looks_like object with Normal = Strange things
Date: 5 Feb 1999 00:39:26
Message: <01bdb5fd$4ed6df60$3f57ae98@default>
I think what you are seeing is what people call "double illumination." It
happens to all povray objects that have a normal applied to them. It isn't
visible most of the time, because most objects won't let you see the
result, due to shadows they create on the inside of themselves.
	If you were to put a light_source in the middle of a sphere that has a
normal, you would see that the sphere is illuminated according to it's
pigment. This is true of all povray objects, and can create interesting
scenes if used correctly.


> Hi, I have noticed that when you have a Look_like inside a light
> source, and you apply it to an object that has a normal modifier, the
> object can be seen even though there is no other light and its ambient
> value is set to 0.


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