POV-Ray : Newsgroups : povray.binaries.images : AABB reduction by Singular Value Decomposition : Re: AABB reduction by Singular Value Decomposition Server Time
15 Jul 2024 08:05:45 EDT (-0400)
  Re: AABB reduction by Singular Value Decomposition  
From: Tor Olav Kristensen
Date: 8 Apr 2021 23:25:00
Message: <web.606fc889d8cfb0ef8e52cc8789db30a9@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Tor Olav Kristensen" <tor### [at] TOBEREMOVEDgmailcom> wrote:
>
> > Sorry: Not "bounding box minimization", but "minimum volume bounding ellipsoid"
>
> Actually, it IS the bounding box we're minimizing.   The ellipsoid is just the
> simplest anisotropic primitive to generate the surface point cloud from, and it
> also comports with the dozens of SVD illustrations online.
>
> Convex hulls and bounding ellipsoids are something I have yet to embark on.

Ok. I see.


> I spent far too long converting a FORTRAN90 subroutine for calculating SVD into
> SDL - which was tricky, given it has a GOTO statement that jumps BACK in the
> code...
> The dozen other GOTOs were pretty straightforward once I saw what I had to do.
>
> I hacked the heck out of it and got it to run with no errors, and spit out some
> matrices, but I don't get any useful results from it.  I'm sure I botched
> something in my marathon editing session, so I have to track down where THIS has
> gone off the rails.

That FORTRAN spaghetti code looks like a little nightmare to rewrite in a
structured way.

I just had a quick look at FORTRAN 90 - and it seems like it could have
been written in a much better way with the features available there.

--
Tor Olav
http://subcube.com
https://github.com/t-o-k


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