Re: 3d programming

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#48

From: Jonathan Cohen
Date: Wed, 14 Feb 1996 22:39

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In article <4ftnfl$p3r@watt.cs.unc.edu>, Jon Leech <leech@cs.unc.edu> wrote:
>In article <4fpm5c$me1@odin.diku.dk>, Niels Ull Jacobsen <null@diku.dk> wrote:
>>Actually, a plane can always be represented by just 3 numbers.
>>
>>The representation Ax+By+Cz=1 works in all but the special case where
>>the plane contains the point (0,0,0). In this case, the plane can be
>>represented as Ax+By+Cz=0 (with an extra degree of freedom).
>
>    Both cases appear to contain 4 numbers - unless '1' and '0'
>are no longer numbers.
>    Pedantically,
>    Jon
>    __@/

Right.  Because you need one number to tell you if the plane passes
through the origin or not.

If we have a particular set of planes we wish to represent, we can
transform them into a coordinate system such that no plane passes
through the origin.  Then we can represent them with 3 numbers each.

Jon C.

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Path: arc1-ca.pugleaf.net!ashe.cs.unc.edu!not-for-mail
From: cohenj@cs.unc.edu (Jonathan Cohen)
Newsgroups: comp.lang.pascal.borland,comp.lang.pascal.mac,comp.lang.pascal.ansi-iso,comp.lang.pascal.misc,comp.sys.amiga.programmer,comp.graphics.algorithms,comp.os.ms-windows.programmer.graphics,comp.sys.amiga.graphics
Subject: Re: 3d programming
Date: 14 Feb 1996 17:39:59 -0500
Organization: The University of North Carolina at Chapel Hill
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