POV-Ray: Newsgroups: povray.bugreports: vaxis

POV-Ray : Newsgroups : povray.bugreports : vaxis_rotate bug		Server Time 31 Oct 2024 21:30:28 EDT (-0400)

From: Craig Shuck
Subject: vaxis_rotate bug
Date: 30 Dec 1998 14:49:09
Message: <368A8340.99D36288@mcdata.com>

The vector function   vaxis_rotate(A,B,F)  generates  "-nan"
for x, y, and z if  B = <0,0,0>.  Modifying x,y, or z by adding
a small amount ( .0001 ) is a partial work-around.

Attached is a simple reproduction.

If this isn't a bug, but just a mathematical "thing", I'm sorry to have
taken your time.

Thanks!

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From: Craig Shuck
Subject: Re: vaxis_rotate bug
Date: 30 Dec 1998 16:04:33
Message: <368A94CF.6D7C0229@mcdata.com>

Oops,

 I'm running POV version 3.1a.watcom.win32
Windows NT 4.0, SP4
Pentium 100 Mhz, 64 MB mem

Craig Shuck wrote:

> The vector function   vaxis_rotate(A,B,F)  generates  "-nan"
> for x, y, and z if  B = <0,0,0>.  Modifying x,y, or z by adding
> a small amount ( .0001 ) is a partial work-around.
>
> Attached is a simple reproduction.
>
> If this isn't a bug, but just a mathematical "thing", I'm sorry to have
> taken your time.
>
> Thanks!

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From: Craig Shuck
Subject: Re: vaxis_rotate bug
Date: 31 Dec 1998 09:55:13
Message: <368B8FE0.D0ACBB69@mcdata.com>

Geez, you'd think I'd know how to attach a file!

Here it is.

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Attachments:
Download 'bugged.pov.txt' (2 KB)

From: PoD
Subject: Re: vaxis_rotate bug
Date: 31 Dec 1998 12:14:01
Message: <368BB0CF.7D71@merlin.net.au>

Craig Shuck wrote:
> 
> The vector function   vaxis_rotate(A,B,F)  generates  "-nan"
> for x, y, and z if  B = <0,0,0>.  Modifying x,y, or z by adding
> a small amount ( .0001 ) is a partial work-around.
> 
> Attached is a simple reproduction.
> 
> If this isn't a bug, but just a mathematical "thing", I'm sorry to have
> taken your time.
> 
> Thanks!

The B is an axis around which to rotate the point eg. if B=<1,0,0> then
the point is rotated around the x axis. If it's <0,0,0>, then it does
not represent a proper axis, which way does the vector <0,0,0> point?

Cheers, PoD.

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From: Tom Galvin
Subject: Re: vaxis_rotate bug
Date: 2 Jan 1999 17:45:22
Message: <368ea182.0@news.povray.org>

>Craig Shuck wrote:
>> If this isn't a bug, but just a mathematical "thing", I'm sorry to have
>> taken your time.
>>
>> Thanks!
>
>The B is an axis around which to rotate the point eg. if B=<1,0,0> then
>the point is rotated around the x axis. If it's <0,0,0>, then it does
>not represent a proper axis, which way does the vector <0,0,0> point?
>
>Cheers, PoD.

This may be related to the divide by zero problem(hate to call user error a
bug).

Garbage in, Garbage Out
Tom

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