Subject:
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Re: Math Problem Again
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 14 Nov 2003 04:26:06 GMT
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Viewed:
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1967 times
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In lugnet.cad.dev, Ronan Webb wrote:
> In lugnet.cad.dev, Tore Eriksson wrote:
> > You are given three 3d cooridates.
>
> (snip) <
> > If possible, I would like an Excel spreadsheet, but just the formula will do.
> >
> > TIA,
> > /Tore
>
>
>
> http://astronomy.swin.edu.au/~pbourke/geometry/planeeq/
>
> (snip) <
> Having worked these out (i.e. this has given you the A,B,C,D in
> A.x + B.y + C.z + D = 0) just plug in your fourth point's x and y co-ords
> (say x4 and y4) into this equation i.e. let x=x4 and let y=y4
> This gives you the equation for z4 that you are looking for viz.
> A.x4 + B.y4 +C.z4 +D =0 (where now the only thing you don't know is z4)
> rearranging this is just
> z4=(-D -A.x4 - B.x4)/C
>
>
> Then again, it's late :)
Hey! cool! where was this info when I wrote my calculator program? It would have made it alot easier. The calculator grew into a slightly different purpose though. it was for helping determine where to trim lines and quads at intersection points.
The last formula had a typo, here it is corrected.
z4=(-D -A.x4 - B.y4)/C
Tore, I will email you the spreadsheet I put this information into.
Paul
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Message has 2 Replies:
 | | Re: Math Problem Again
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| (...) Yes, I saw that, too. (...) Thanks for the offer, but I have already made a working spreadsheet. :) Now, all I have to do is try to automate it with some VBS. /Tore (20 years ago, 14-Nov-03, to lugnet.cad.dev)
| | | calc_z4.c (Was: Math Problem Again)
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| (...) Sorry guys, just wanted to store this function in a safer place than my hard drive. :) I just don't want to remake it again...! Feel free to copy/paste/edit/port if you need it! /Tore // calc_z4 by Tore Eriksson // credits to Ronan Webb for (...) (15 years ago, 22-Oct-09, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: Math Problem Again
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| (...) (URL) you how to derive the equation of a plane passing thru the three points (x1,y1,z1) (x2,y2,z2) (x3,y3,z3) The standard equation of a plane in 3 space is A.x + B.y + C.z + D = 0 (where the "." means times) So given three points in space (...) (20 years ago, 14-Nov-03, to lugnet.cad.dev)
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