Article View: comp.lang.pascal.borland
Article #66Re: 3d programming
From: Jeffrey Karl Lassahn
Date: Mon, 26 Feb 1996 01:59
Date: Mon, 26 Feb 1996 01:59
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Christopher H. Clark (chc104@psu.edu) wrote: : Jonathan Cohen wrote: : > : > In article <3118310E.52F@psu.edu>, Christopher H. Clark <chc104@psu.edu> wrote: : > >Actually, you only need 2 points to define a plane: a point on the plane and : > >a normal vector. : > : > Sorry to quibble, but... : > : > A VECTOR IS NOT A POINT!!!! : > : > Now back to our regular program. : Points are vectors. : -Chris All this is just a matter of terminology. Instead of "normal vector" can say "second point such that the plane chosen makes the two points lie on a perpendicular line to the plane." Then the two points specify the plane quite nicely. By the way, two points in 3space are specified by 6 real numbers. If you like, you can specify a plane in 4 numbers: the solution to Ax + By + Cz + D = 0 is a unique plane for A,B,C not all 0. It's also easy to transform using matrixes and such, and can sometimes save you some computer time.
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Path: arc1-ca.pugleaf.net!nntp.teleport.com!jkl From: jkl@teleport.com (Jeffrey Karl Lassahn) 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 Followup-To: 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 Date: 26 Feb 1996 01:59:31 GMT Organization: Teleport - Portland's Public Access (503) 220-1016 Message-ID: <4gr464$1is@maureen.teleport.com> References: <4f3od9$2jg@zeus.tcp.co.uk> <jderrick-0502961551360001@slip037.csc.cuhk.hk> <3118310E.52F@psu.edu> <4fiuh2$qrj@fulton.cs.unc.edu> <311E38D7.71BC@psu.edu> NNTP-Posting-Host: julie.teleport.com X-Newsreader: TIN [version 1.2 PL2]