Subject:
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Re: Is it possible to use LDView as POV-Ray previewer?
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Newsgroups:
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lugnet.cad.ray
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Date:
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Tue, 6 Dec 2005 21:44:57 GMT
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Viewed:
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7900 times
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In lugnet.cad.ray, Travis Cobbs wrote:
> In lugnet.cad.ray, Timothy Gould wrote:
> > None handy but all I'd do is sort first and then perpendicularise one and use
> > the cross-product for the third. Probably what you do anyway.
> >
> > To be honest I don't see why POVray is being so pedantic about it. It's only
> > going to be accurate matter to about 1/2000 unless you raytrace massive images.
>
> I'm not sure what you mean by "sort first". However, I do what you say, and
> make the right and up perpendicular, then use the cross product to determine the
> direction. POV-Ray is only pedantic when the "vista buffer" is enabled (which
> is true by default). I'm not sure what the "vista buffer" does, or how
> sensitive it is to accuracy, but it goes without saying that there will always
> be round-off errors.
>
> --Travis
By sort first I mean I would find which vector is most-orthogonal (ie. the one
whose dot protucts were smallest compared to the other two) and leave it be,
then I'd perpendicularise the one whose dot-product was smallest with the first
one and then I'd set the third one as the cross-product of those two.
I'm sure there is a way (probably involving the eigenvectors of the original
matrix) which guarantees that the new basis set has the smallest sum of dot
products with the first set but that is probably going too far.
As for "vista buffer"... I have no idea. There aren't only round-off errors
though since we are finding a discrete image (the pixels) there is a relatively
large 'error' from that too.
Tim
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Message is in Reply To:
 | | Re: Is it possible to use LDView as POV-Ray previewer?
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| (...) I'm not sure what you mean by "sort first". However, I do what you say, and make the right and up perpendicular, then use the cross product to determine the direction. POV-Ray is only pedantic when the "vista buffer" is enabled (which is true (...) (19 years ago, 6-Dec-05, to lugnet.cad.ray)
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