POV-Ray : Newsgroups : povray.text.scene-files : [Minimum Volume] Bounding Ellipsoid via SVD : Re: [Minimum Volume] Bounding Ellipsoid via SVD Server Time
23 Jun 2024 14:19:08 EDT (-0400)
  Re: [Minimum Volume] Bounding Ellipsoid via SVD  
From: Bald Eagle
Date: 6 Nov 2019 20:35:00
Message: <web.5dc374c1f7b9a3af4eec112d0@news.povray.org>
"jr" <cre### [at] gmailcom> wrote:

> > my command line directive is:
> > c++ SVD_BW.cpp -std=c++11
>          ^^^
> spot the difference.  ;-)  no matter though, it can wait until you've changed it
> to read data from stdin.

Spot the identity.  ;P
http://news.povray.org/povray.text.scene-files/message/%3Cweb.5dc33dd7f7b9a3af4eec112d0%40news.povray.org%3E/#%3Cweb.5d
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I don't know what construct to use to "catch" the data from stdin...
But I will look.
Hangin' it up for the day - got a day tomorrow, hopefully it's not a disaster
<crosses fingers>


> it is .. seductive.  _if_ I can understand yr code well enough, I've plans for a
> platform on tank-like tracks I'd like to build.

I'll see if I can put together a simplified version minus all the gobbledygook.


> > I hope the lesson pdf clarifies the whole point of all of this and to some
> > extent how it's done.
>
> you're pulling my leg..

Nope.
Just look at the pretty pictures.

> had a quick scan, the formulae just make my eyes bleed.
>  the 1st scan main benefit was seeing the virtual "mass", as an assumption and
> how it can then be applied.  that, as a concept, is v interesting, need to think
> on it.

Well that's basically it - don't look at the formulae.

The real gist looks to be that matrices encode (mostly) scaling and rotations.
 One matrix can be split up (factored) into a rotation matrix, a reverse
rotation matrix (which obviously cancel) and a matrix of scaling factors.

So "How is your data stretched?"  It stretches along "x" by this much, "Y" by
this much, and "z" by this much.
And the rotation matrix tells you what direction "x", "y" and "z" are from the
real, cardinal basis vectors of <x, y, z>.


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