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28 Mar 2024 10:08:37 EDT (-0400)
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From: Ron Parker
Subject: Re: truncated cubes.
Date: 9 Oct 2000 11:22:58
Message: <slrn8u3ohq.1jk.ron.parker@fwi.com>
On Mon, 09 Oct 2000 08:27:41 -0400, Greg M. Johnson wrote:
>Thanks, but what I meant is this:
>
>Take  perfect cube.  set each edge on a grinding wheel such that the normal of
>the two faces on this edge make a 45 degree angle with the normal of the
>grinding wheel.  Do it for just a second or two.

So what you want is a cube with beveled edges.  The size of the bevel is a
factor in finding the corners.

What used to be a square face will still be a square face, but it will be 
moved inward on all sides by the size of the bevel.  What used to be an edge
will now be a rectangular face; connect corresponding edges of the new square
faces to find the twelve new faces.  What used to be a vertex will now be a
triangular face; connect corresponding corners of the new square faces to 
find the eight new faces.  The final object will have 26 faces, with a total 
of 44 triangles.

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.
Proudly not helping RIAA and SDMI steal my rights -- 
  http://www.eff.org/Misc/EFF/Newsletters/EFFector/HTML/effect13.08.html


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From: Ken
Subject: Re: Concave shapes (43KB)
Date: 9 Oct 2000 11:56:16
Message: <39E1E972.407515C7@pacbell.net>
Jamie Davison wrote:

> I had a look at that URL, and it seems that the Surface Subdivision Suite
> page has moved to /dev/null <grin>, as the URL you posted points to a new
> page, which gives a 404...

Hmmm.... I'll see if I can track it down.

-- 
Ken Tyler


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From: Tor Olav Kristensen
Subject: Re: truncated cubes.
Date: 9 Oct 2000 14:43:37
Message: <39E210D5.A2979329@online.no>
Ron Parker wrote:

> ...
> So what you want is a cube with beveled edges.  The size of the bevel is a
> factor in finding the corners.
>
> What used to be a square face will still be a square face, but it will be
> moved inward on all sides by the size of the bevel.  What used to be an edge
> will now be a rectangular face; connect corresponding edges of the new square
> faces to find the twelve new faces.  What used to be a vertex will now be a
> triangular face; connect corresponding corners of the new square faces to
> find the eight new faces.  The final object will have 26 faces, with a total
> of 44 triangles.

Are you sure about all this ?   :)

See enclosed image.


To Greg:
When I've cleaned up the source code (that I believe
solves your problem), I'll post it.


Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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Attachments:
Download 'truncatedcube03.jpg' (18 KB)

Preview of image 'truncatedcube03.jpg'
truncatedcube03.jpg


 

From: Tor Olav Kristensen
Subject: Re: Concave shapes (43KB)
Date: 9 Oct 2000 16:58:39
Message: <39E23080.DA437FE3@online.no>
Philip Cowley wrote:

> > Yesterday I did some more work on some CSG-macros of mine.
> > They will "round off" any concave shape made with intersections
> > of planes, like the upper left shape.
>
> Any chance of you posting the macro code itself...

Yes I will. -But it needs some more work first.

Right now I'm too tired to do this work.


Tor Olav
--
mailto:tor### [at] hotmailcom
http://www.crosswinds.net/~tok/tokrays.html


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From: David Fontaine
Subject: Re: truncated cubes.
Date: 9 Oct 2000 17:12:37
Message: <39E23260.EB784E5@faricy.net>
"Greg M. Johnson" wrote:

> Thanks, but what I meant is this:
>
> Take  perfect cube.  set each edge on a grinding wheel such that the normal of
> the two faces on this edge make a 45 degree angle with the normal of the
> grinding wheel.  Do it for just a second or two.

Ah, that's bevelled, not truncated :) (Besides i think my data was wrong, it
should have been (2-sqrt(2)) for perfect octagon)
so you want a perfect octagon for the cross section? hmm...






24 vertices, 18 faces, 60 triangles

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


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From: Bob H 
Subject: Re: Concave shapes (43KB)
Date: 9 Oct 2000 19:11:51
Message: <39e250b7@news.povray.org>
"Ken" <tyl### [at] pacbellnet> wrote in message
news:39E1E972.407515C7@pacbell.net...
|
| Jamie Davison wrote:
|
| > the URL you posted points to a new page, which gives a 404...
|
| Hmmm.... I'll see if I can track it down.

Only the last of those 4 addresses worked for me.  No wonder I couldn't
locate anything, and I had misspelled Steven Pigeons' name (sorry Steve).
Anyhow, not sure any of this goes with what Tor has done since the rocks all
seem to be triangle mesh instead of plane intersections.

Bob


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From: Tor Olav Kristensen
Subject: Re: truncated cubes.
Date: 10 Oct 2000 20:19:44
Message: <39E3B121.D80F0C6E@online.no>
"Greg M. Johnson" wrote:

> Thanks, but what I meant is this:
>
> Take  perfect cube.  set each edge on a grinding wheel such that the normal of
> the two faces on this edge make a 45 degree angle with the normal of the
> grinding wheel.  Do it for just a second or two.
> ...

I've now posted some source code that provides you with the coordinates
for the corners. (Watch the output in the debug window.)

See my recent post "Source code for bevelled box" to povray.text.scene-files:

news://news.povray.org/39E3AFCA.B8FB8283%40online.no


Regards,

Tor Olav


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From: Ken
Subject: Re: Concave shapes (43KB)
Date: 11 Oct 2000 00:09:47
Message: <39E3E6D3.D03F7949@pacbell.net>
"Bob H." wrote:
> 
> "Ken" <tyl### [at] pacbellnet> wrote in message
> news:39E1E972.407515C7@pacbell.net...
> |
> | Jamie Davison wrote:
> |
> | > the URL you posted points to a new page, which gives a 404...
> |
> | Hmmm.... I'll see if I can track it down.
> 
> Only the last of those 4 addresses worked for me.  No wonder I couldn't
> locate anything, and I had misspelled Steven Pigeons' name (sorry Steve).
> Anyhow, not sure any of this goes with what Tor has done since the rocks all
> seem to be triangle mesh instead of plane intersections.
> 
> Bob

After contacting John the Subdivision Surface Suite is now back online
at - http://users4.50megs.com/enphilistor/sss.htm

Steven's page is still valid as is Mack Stocks page. The only one
that appears to be gone is "Rocks" at -

http://www.rahul.net/endl/mallan/html/rocks.htm

for which there appears to be no replacement URL for.

Three out of four ain't bad :)

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/


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From: Greg M  Johnson
Subject: Re: truncated cubes.
Date: 12 Oct 2000 08:59:58
Message: <39E5B473.5CFF8783@my-dejanews.com>
Oh my dear friend, I am sorry. I wanted triangles.  Let me figure it out myself.  I
am a newbie at discovering the benefits of triangles.    If I were to use the
intersection of a dozen or more planes, I might as well have used a superellipsoid.


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Attachments:
Download 'cells.jpg' (21 KB)

Preview of image 'cells.jpg'
cells.jpg


 

From: Defective
Subject: Re: truncated cubes.
Date: 3 Dec 2000 01:59:25
Message: <f8rj2t8d0mp38q5krhkb3tgkttr1qbp4mn@4ax.com>
On Mon, 09 Oct 2000 08:27:41 -0400, "Greg M. Johnson"
<gre### [at] my-dejanewscom> blathered:

>Thanks, but what I meant is this:
>
>Take  perfect cube.  set each edge on a grinding wheel such that the normal of
>the two faces on this edge make a 45 degree angle with the normal of the
>grinding wheel.  Do it for just a second or two.
>
>

Let me first state that I've read the rest of this thread (as of this
date) and know my answer is not what you're looking for.

This description (above) leads me to describing how I figure out the
appropriate method for creating a shape.  If I were creating a cube
that I wanted to look like it had the corners knocked off with a
grinder, I tend to create the cube, then use a CSG difference to
remove the parts the grinder took away.  In other words, I try to
create the effect of the manufacturing process.

<inside_voice> Pinot Gris has an odd effect on my thought
processes...</inside_voice>

I'd create the cube, then create my imaginary grinding wheel.  Then
I'd use a CSG difference (or maybe a few thousand...) to remove the
corners.



Defective O-O

http://members.home.com/redundant/Defective/
(yes, I know that's the wrong membername...ran out of space at
http://members.home.com/defective/)


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