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  I am calculating a normal... (Message 1 to 6 of 6)  
From: Jim Charter
Subject: I am calculating a normal...
Date: 27 Feb 2002 23:29:42
Message: <3C7DB22D.2000107@aol.com>
and my calculation returns the following values:

< -1.#IND000,-1.#IND000,-1.#IND000 >

can anyone help me make sense of this?

Bottom line, I just need to know how to test for these and give them a 
skip when they occur.


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From: Mark Wagner
Subject: Re: I am calculating a normal...
Date: 28 Feb 2002 00:41:20
Message: <3c7dc300@news.povray.org>
Jim Charter wrote in message <3C7### [at] aolcom>...
>and my calculation returns the following values:
>
>< -1.#IND000,-1.#IND000,-1.#IND000 >
>
>can anyone help me make sense of this?
>
>Bottom line, I just need to know how to test for these and give them a
>skip when they occur.

Without seeing the code you are using, I can't tell you for certain.
 The -1.#IND means that a recent calculation had an undefined result.  I'm
guessing you're dividing by zero somewhere.  Do your calculations normalize
the vector?

--
Mark


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From: Jim Charter
Subject: Re: I am calculating a normal...
Date: 28 Feb 2002 05:47:02
Message: <3C7E0AA1.4050903@aol.com>
Mark Wagner wrote:

  
> 
> Without seeing the code you are using, I can't tell you for certain.
>  The -1.#IND means that a recent calculation had an undefined result.  I'm
> guessing you're dividing by zero somewhere.  Do your calculations normalize
> the vector?
> 
> --
> Mark
> 
 Thanks Mark, as it turns out it is not really a show stopper

I tested:  #if ( Norm.x = -1 & Norm.y = -1 & Norm.z = -1 )
			don't use Norm
crude, I know, but good enough in this case


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From:
Subject: Re: I am calculating a normal...
Date: 28 Feb 2002 05:55:14
Message: <vo2s7uc355p2c5e52bea9uva2ibjbqcndt@4ax.com>
On Thu, 28 Feb 2002 05:46:57 -0500, Jim Charter <jrc### [at] aolcom> wrote:
> I tested:  #if ( Norm.x = -1 & Norm.y = -1 & Norm.z = -1 )

AFAIK

-1 != -1.#IND

btw: I didn't found any place in 3.5 documentation where "#IND" is noted
and/or explained. It can confuse newbies.

ABX


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From: Thorsten Froehlich
Subject: Re: I am calculating a normal...
Date: 28 Feb 2002 06:18:05
Message: <3c7e11ed@news.povray.org>

Skiba <abx### [at] babilonorg>  wrote:

> AFAIK
>
> -1 != -1.#IND
>
> btw: I didn't found any place in 3.5 documentation where "#IND" is noted
> and/or explained. It can confuse newbies.

It is an artifact of the C library used.  Results may be different for
different C libraries and thus this cannot be noted in the documentation.
Further, checking for NANs and other invalid floating-point values was not
part of the C standard until C99, so many compilers don't support those recent
improvements yet.  For this reason, it remains the users' responsibility to
only feed valid input into the various floating-point calculations in order to
get valid output...

    Thorsten

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

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


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From: Jim Charter
Subject: Re: I am calculating a normal...
Date: 28 Feb 2002 16:53:51
Message: <3C7EA6E7.7010607@aol.com>
Thankyou again for the explanation.  My SDL was not well-formed and the 
bad input was most likely do to sloppy loop control.  Since it happened 
at the end of a loop, it was just as easy to drop the offending 
calculation.

Thorsten Froehlich wrote:

> In article <vo2s7uc355p2c5e52bea9uva2ibjbqcndt@4ax.com> , W"odzimierz ABX 
> Skiba <abx### [at] babilonorg>  wrote:
> 
> 
>>AFAIK
>>
>>-1 != -1.#IND
>>
>>btw: I didn't found any place in 3.5 documentation where "#IND" is noted
>>and/or explained. It can confuse newbies.
>>
> 
> It is an artifact of the C library used.  Results may be different for
> different C libraries and thus this cannot be noted in the documentation.
> Further, checking for NANs and other invalid floating-point values was not
> part of the C standard until C99, so many compilers don't support those recent
> improvements yet.  For this reason, it remains the users' responsibility to
> only feed valid input into the various floating-point calculations in order to
> get valid output...
> 
>     Thorsten
> 
> ____________________________________________________
> Thorsten Froehlich, Duisburg, Germany
> e-mail: tho### [at] trfde
> 
> Visit POV-Ray on the web: http://mac.povray.org
>


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