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From: Martin Thoma
Subject: Disc which is not flat
Date: 29 Nov 2001 07:29:01
Message: <3C0629CF.B3EABB60@radiok2r.de>
Hello! How can I make a disc which is not infinite flat?!

Martin


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From: Nekar Xenos
Subject: Re: Disc which is not flat
Date: 29 Nov 2001 07:36:24
Message: <3c062bc8@news.povray.org>
Do you mean something like this?

sphere{0,1 scale y*.1}

or maybe this?

cylinder {y,-y,1 scale y*.1}

--
- Nekar

http://nekar_xenos.tripod.com/metanoia/

"Martin Thoma" <mar### [at] radiok2rde> wrote in message
news:3C0629CF.B3EABB60@radiok2r.de...
> Hello! How can I make a disc which is not infinite flat?!
>
> Martin
>
>


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From: David Fontaine
Subject: Re: Disc which is not flat
Date: 29 Nov 2001 18:24:34
Message: <3C06C487.19BEFCB2@faricy.net>
Nekar Xenos wrote:
> 
> cylinder {y,-y,1 scale y*.1}

That should be scale <1,.1,1>

-- 
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/


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From: Nekar Xenos
Subject: Re: Disc which is not flat
Date: 30 Nov 2001 01:49:22
Message: <3c072bf2@news.povray.org>
"David Fontaine" <dav### [at] faricynet> wrote in message
news:3C06C487.19BEFCB2@faricy.net...
> Nekar Xenos wrote:
> >
> > cylinder {y,-y,1 scale y*.1}
>
> That should be scale <1,.1,1>
>
I didn't know there's a difference. Can you please explain that to me?

Thanks,
--
- Nekar

http://nekar_xenos.tripod.com/metanoia/



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From: Slime
Subject: Re: Disc which is not flat
Date: 30 Nov 2001 02:37:33
Message: <3c07373d$1@news.povray.org>
y*.1 is equivalent to <0,.1,0>. You can't scale an object by zero in any
direction - it's like squishing it to zero thickness, and there are
mathematical reasons why the concept doesn't work (it relates to division by
zero). You'll notice that when you use something like that, POV-Ray gives
you a warning saying that you can't scale by zero, and it's replacing the
zeros with ones. That's usually the intended behavior, as you just
demonstrated. I usually don't worry about the warnings, since it's pretty
obvious what my intent is when I say scale y*.1, but if you want to be
really correct about it, use scale <1,.1,1> or scale y*.1 +x+z.

--
- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]
"Nekar Xenos" <j-p### [at] citywalkcoza> wrote in message
news:3c072bf2@news.povray.org...
>
> "David Fontaine" <dav### [at] faricynet> wrote in message
> news:3C06C487.19BEFCB2@faricy.net...
> > Nekar Xenos wrote:
> > >
> > > cylinder {y,-y,1 scale y*.1}
> >
> > That should be scale <1,.1,1>
> >
> I didn't know there's a difference. Can you please explain that to me?
>
> Thanks,
> --
> - Nekar
>
> http://nekar_xenos.tripod.com/metanoia/
>
>
>
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> Outgoing mail is certified Virus Free.
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> Version: 6.0.298 / Virus Database: 161 - Release Date: 2001/11/13
>
>


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From: Nekar Xenos
Subject: Re: Disc which is not flat
Date: 30 Nov 2001 03:41:41
Message: <3c074645@news.povray.org>
"Slime" <noo### [at] hotmailcom> wrote in message
news:3c07373d$1@news.povray.org...
> y*.1 is equivalent to <0,.1,0>. You can't scale an object by zero in any
> direction - it's like squishing it to zero thickness, and there are
> mathematical reasons why the concept doesn't work (it relates to division by
> zero). You'll notice that when you use something like that, POV-Ray gives
> you a warning saying that you can't scale by zero, and it's replacing the
> zeros with ones. That's usually the intended behavior, as you just
> demonstrated. I usually don't worry about the warnings, since it's pretty
> obvious what my intent is when I say scale y*.1, but if you want to be
> really correct about it, use scale <1,.1,1> or scale y*.1 +x+z.
>

Thanks. I've always wondered about all those warnings...   ;)

--
- Nekar

http://nekar_xenos.tripod.com/metanoia/



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From: Warp
Subject: Re: Disc which is not flat
Date: 30 Nov 2001 08:41:05
Message: <3c078c70@news.povray.org>
Slime <noo### [at] hotmailcom> wrote:
: y*.1 is equivalent to <0,.1,0>. You can't scale an object by zero in any
: direction - it's like squishing it to zero thickness, and there are
: mathematical reasons why the concept doesn't work (it relates to division by
: zero).

  The exact reason is that POV-Ray doesn't actually transform the object at
all, but it instead transforms the ray with the inverse transformation when
the ray-object intersection is tested.
  The inverse transformation of scale <0, .1, 0> is scale <1/0, 1/.1, 1/0>.

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -


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From: Tom Melly
Subject: Re: Disc which is not flat
Date: 30 Nov 2001 11:50:10
Message: <3c07b8c2@news.povray.org>
"Warp" <war### [at] tagpovrayorg> wrote in message news:3c078c70@news.povray.org...

What are the chances of having this warning removed?


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From:
Subject: Re: Disc which is not flat
Date: 30 Nov 2001 12:15:50
Message: <9hff0ukmosl6k7thmfmi1nlvsdkkgd9q6v@4ax.com>
On Fri, 30 Nov 2001 16:50:05 -0000, "Tom Melly" <tom### [at] tomandlucouk> wrote:
> What are the chances of having this warning removed?

Personally I prefer when software inform me when he know better what shuld be
passed and change values. But if you don't like it you can check "-GW" ini
switch.

ABX
--
#declare _=function(a,b,x){((a^2)+(b^2))^.5-x}#default {pigment{color rgb 1}}
union{plane{y,-3}plane{-x,-3}finish{reflection 1 ambient 0}}isosurface{ //ABX
function{_(x-2,y,1)|_((x+y)*.7,z,.1)|_((x+y+2)*.7,z,.1)|_(x/2+y*.8+1.5,z,.1)}
contained_by{box{<0,-3,-.1>,<3,0,.1>}}translate z*15finish{ambient 1}}//POV35


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From: Rune
Subject: Re: Disc which is not flat
Date: 30 Nov 2001 12:36:52
Message: <3c07c3b4@news.povray.org>
"Tom Melly" wrote:
> What are the chances of having this warning removed?

100%. Use the command line setting -gw.

Seriously, I don't want it to be removed. I've encountered lots of cases
where the correction of the 0's to 1's were not desired. For example if I
have a matrix that due to an error scales the object by 0 in one direction.
If not I was warned it would be extremely difficult to find out what's going
on. It also happens often that a while loop or similar that scales an object
smaller and smaller reaches 0 due to a bug in the script, and then the
object is suddenly scaled by 1. I want to be warned about that.

Rune
--
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