POV-Ray : Newsgroups : povray.animations : Illegal scaling, that is'nt illegal... Server Time: 23 Oct 2019 03:25:00 GMT
  Illegal scaling, that is'nt illegal... (Message 1 to 7 of 7)  
From: H  Karsten
Subject: Illegal scaling, that is'nt illegal...
Date: 15 Dec 2009 06:50:01
Message: <web.4b273165d6d77fe7da6353d60@news.povray.org>
Hi people,

I've just made an animation with some _wanted_ zero-scalings in some frames.

Do anybody know a way to tell PovRay to scale the objects to zero, instead of
scaling them to one, and give me heaps of error messages?

Holger


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From: Stephen
Subject: Re: Illegal scaling, that is'nt illegal...
Date: 15 Dec 2009 08:01:49
Message: <4b27426d@news.povray.org>
H. Karsten wrote:
> Hi people,
> 
> I've just made an animation with some _wanted_ zero-scalings in some frames.
> 
> Do anybody know a way to tell PovRay to scale the objects to zero, instead of
> scaling them to one, and give me heaps of error messages?
> 
> Holger
> 
> 
Hi Holgar,
	Even though you want to scale something to zero you can’t, as you found 
out. The best you can do is scale very, very small (0.0000001?).


-- 

Best Regards,
	Stephen


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From: H  Karsten
Subject: Re: Illegal scaling, that is'nt illegal...
Date: 15 Dec 2009 08:40:00
Message: <web.4b274b27c9eeb80dda6353d60@news.povray.org>
Well this would be maybe an option for the version 4.


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From: Stephen
Subject: Re: Illegal scaling, that is'nt illegal...
Date: 15 Dec 2009 11:11:50
Message: <4b276ef6$1@news.povray.org>
H. Karsten wrote:
> Well this would be maybe an option for the version 4.
> 
> 
> 
> 
LOL but seriously why do you want to scale things to zero? If I want to 
show something getting larger from nothing I initially translate it out 
of view then using a “step jump” translate it into view and scale it up 
from a small value.

-- 

Best Regards,
	Stephen


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From: Mike Williams
Subject: Re: Illegal scaling, that is'nt illegal...
Date: 15 Dec 2009 12:35:06
Message: <V8qHR9B1J4JLFw+w@econym.demon.co.uk>
Wasn't it Stephen who wrote:
>H. Karsten wrote:
>> Well this would be maybe an option for the version 4.
>>
>LOL but seriously why do you want to scale things to zero? If I want to 
>show something getting larger from nothing I initially translate it out 
>of view then using a “step jump” translate it into view and scale 
>it up from a small value.

If we're talking about zero in all three dimensions, then it would be 
efficient to put all the objects inside if statements, and skip the 
parsing and rendering if the scale is zero. Perhaps using a macro that 
accepts an object and a scale factor if there are many such objects to 
be handled.

However, the warning and the defaulting to 1.0 happen if only one of the 
dimensions is scaled to zero. Perhaps Holger wants the objects to be 
scaled infinitely thin, like part of a plane. With the current 
behaviour, if you try to scale an object infinitely thin in one 
direction, the parser thinks you've missed that parameter and scales it 
to 1.0.

I can imagine some of the ray intersection solvers having big problems 
with objects that really do have zero thickness, because they're trying 
to find points where the ray goes from outside to inside something, and 
that doesn't really happen if the object has no thickness. [Note that 
thin objects like planes don't have that problem because they consider 
half the universe to be inside.]

I can also imagine compound objects, like unions, suffering from 
coincident surface artefacts wherever two components with different 
textures overlap.

-- 
Mike Williams
Gentleman of Leisure


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From: Stephen
Subject: Re: Illegal scaling, that is'nt illegal...
Date: 15 Dec 2009 21:00:12
Message: <4b27f8dc@news.povray.org>
Mike Williams wrote:
> Wasn't it Stephen who wrote:
>> H. Karsten wrote:
>>> Well this would be maybe an option for the version 4.
>>>
>> LOL but seriously why do you want to scale things to zero? If I want 
>> to show something getting larger from nothing I initially translate it 
>> out of view then using a “step jump” translate it into view and scale 
>> it up from a small value.
> 
> If we're talking about zero in all three dimensions, then it would be 
> efficient to put all the objects inside if statements, and skip the 
> parsing and rendering if the scale is zero. Perhaps using a macro that 
> accepts an object and a scale factor if there are many such objects to 
> be handled.

Yes, that is a better way of doing it. I was thinking of my use of a 
modeller that could not utilise #if or #case statements.

> 
> However, the warning and the defaulting to 1.0 happen if only one of the 
> dimensions is scaled to zero. Perhaps Holger wants the objects to be 
> scaled infinitely thin, like part of a plane. With the current 
> behaviour, if you try to scale an object infinitely thin in one 
> direction, the parser thinks you've missed that parameter and scales it 
> to 1.0.
> 
> I can imagine some of the ray intersection solvers having big problems 
> with objects that really do have zero thickness, because they're trying 
> to find points where the ray goes from outside to inside something, and 
> that doesn't really happen if the object has no thickness. [Note that 
> thin objects like planes don't have that problem because they consider 
> half the universe to be inside.]
> 
> I can also imagine compound objects, like unions, suffering from 
> coincident surface artefacts wherever two components with different 
> textures overlap.
> 

You put what I was thinking into a well defined statement. I wrote in 
haste and now repent in leisure ;)
-- 

Best Regards,
	Stephen


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From: W0RLDBUILDER
Subject: Re: Illegal scaling, that is'nt illegal...
Date: 29 Apr 2011 23:05:00
Message: <web.4dbb43a5c9eeb80db6f0ad930@news.povray.org>
"H. Karsten" <h-karsten()web.de> wrote:
> Hi people,
>
> I've just made an animation with some _wanted_ zero-scalings in some frames.
>
> Do anybody know a way to tell PovRay to scale the objects to zero, instead of
> scaling them to one, and give me heaps of error messages?
>
> Holger

Mayor Kravindish: This is illegal, you know.


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