POV-Ray : Newsgroups : povray.general : Another kind of scaling or "growing" Server Time
5 Aug 2024 04:17:11 EDT (-0400)
  Another kind of scaling or "growing" (Message 1 to 7 of 7)  
From: Jellby
Subject: Another kind of scaling or "growing"
Date: 15 Dec 2002 15:20:24
Message: <3dfce408@news.povray.org>
Hello,

Have you ever felt that the standard scaling is not what you need? I was 
thinking about that and it occurred to me that it could be interesting to 
be able to grow or shrink an object not relative to the origin (as with the 
standard scaling) but perpendicularly to its surface. Does this have any 
sense? It would be equivalent for some simple shapes: sphere, cube... but 
for others it would be like changing the threshold value (for blobs), or 
altering the minor radius (for tori)...

I know this is more than probably not easy (impossible?) to do, and maybe 
it's not interesting at all, but well, I lose nothing by writing it here :)

Regards

-- 

Linux User #289967 (counter.li.org)
PGP Pub Key ID: 0x01A95F99 (pgp.escomplinux.org)


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From: Tim Nikias
Subject: Re: Another kind of scaling or "growing"
Date: 15 Dec 2002 17:58:17
Message: <3dfd0909@news.povray.org>
I think the way POV-Ray works does not make
this possible. Perhaps using functions, or Horman's
isoCSG, but I'm not too sure about that. After all, you
are talking about a double step: find the surface, get
the normal, and then move surface in opposite direction
to normal...
This may work very easy with meshes, but not with
mathematical solutions, and especially not a jumbled
mess of them (which a union/merge normally is)...

--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde
"Jellby" <jel### [at] M-yahoocom> schrieb im Newsbeitrag
news:3dfce408@news.povray.org...
> Hello,
>
> Have you ever felt that the standard scaling is not what you need? I was
> thinking about that and it occurred to me that it could be interesting to
> be able to grow or shrink an object not relative to the origin (as with
the
> standard scaling) but perpendicularly to its surface. Does this have any
> sense? It would be equivalent for some simple shapes: sphere, cube... but
> for others it would be like changing the threshold value (for blobs), or
> altering the minor radius (for tori)...
>
> I know this is more than probably not easy (impossible?) to do, and maybe
> it's not interesting at all, but well, I lose nothing by writing it here
:)
>
> Regards
>
> --

> Linux User #289967 (counter.li.org)
> PGP Pub Key ID: 0x01A95F99 (pgp.escomplinux.org)


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From: Slime
Subject: Re: Another kind of scaling or "growing"
Date: 15 Dec 2002 18:12:54
Message: <3dfd0c76@news.povray.org>
> Have you ever felt that the standard scaling is not what you need? I was
> thinking about that and it occurred to me that it could be interesting to
> be able to grow or shrink an object not relative to the origin (as with
the
> standard scaling) but perpendicularly to its surface. Does this have any
> sense? It would be equivalent for some simple shapes: sphere, cube... but
> for others it would be like changing the threshold value (for blobs), or
> altering the minor radius (for tori)...


It's been thought of before, and while possible with some shapes, it's very
difficult (and analytically impossible for certain shapes).

Mega-POV's "proximity pattern" did this, I think.

 - Slime
[ http://www.slimeland.com/ ]


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From: Christopher James Huff
Subject: Re: Another kind of scaling or "growing"
Date: 16 Dec 2002 00:00:59
Message: <chrishuff-327099.23572815122002@netplex.aussie.org>
In article <3dfd0c76@news.povray.org>, "Slime" <slm### [at] slimelandcom> 
wrote:

> Mega-POV's "proximity pattern" did this, I think.

Sort of: the proximity pattern used the average or minimum distance to 
the surface. Theoretically, this could be used in an isosurface to do 
this "inflate" effect, but the original pattern was almost unuseably 
slow in textures (on computers of that time), as an isosurface function 
it would be extremely slow. I'm working on an updated version that has 
optimized object-specific proximity methods in addition to the 
ray-sampling method.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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From: Greg M  Johnson
Subject: Re: Another kind of scaling or "growing"
Date: 16 Dec 2002 08:20:48
Message: <3dfdd330@news.povray.org>
Write your own macro to do this using the trace function.

This confusing double-set of coordinates made use of CorelDream3D a
confusing waste of time...


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From: Le Forgeron
Subject: Re: Another kind of scaling or "growing"
Date: 17 Dec 2002 11:37:25
Message: <3DFF52DD.9060003@free.fr>
Jellby wrote:

> Hello,
> 
> Have you ever felt that the standard scaling is not what you need? I was 
> thinking about that and it occurred to me that it could be interesting to 
> be able to grow or shrink an object not relative to the origin (as with the 
> standard scaling) but perpendicularly to its surface. Does this have any 
> sense? It would be equivalent for some simple shapes: sphere, cube... but 
> for others it would be like changing the threshold value (for blobs), or 
> altering the minor radius (for tori)...
> 
> I know this is more than probably not easy (impossible?) to do, and maybe 
> it's not interesting at all, but well, I lose nothing by writing it here :)


It's been done already (as a patch of 3.1) for mesh,
  see http://jgrimbert.free.fr/pov/patch/tessel/index.html#displace
It works better with smoothed mesh, because otherwise the 
displacement/growth along the normal create a lot of holes in the mesh
(but that can be a desired effect...)

Given the way Pov works, your idea is only possible with mesh and 
mesh-compatible objects.


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From: Jellby
Subject: Re: Another kind of scaling or "growing"
Date: 17 Dec 2002 14:44:51
Message: <3dff7eb3@news.povray.org>
OK, thanks for the replies.

I understand it's difficult/impossible to implement in POV, and I didn't 
intend to suggest that, I was just trying to start a conversation about it 
:)
I guess meshes (and macros) would be the way to go for this. How hard would 
be to take into account the possible spliting of the object? It's been a 
long time since I last made anything in POV, and I don't have much time 
now, so this is just a "thought experiment".

-- 

Linux User #289967 (counter.li.org)
PGP Pub Key ID: 0x01A95F99 (pgp.escomplinux.org)


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