Article View: comp.graphics.algorithms
Article #48Re: 3d programming
From: Samuel P. Uselton
Date: Fri, 23 Feb 1996 18:45
Date: Fri, 23 Feb 1996 18:45
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OK. A point specifies a location, in a space of any dimension. It has no magnitude (= size, or "dimensions" in an engineering or architectural sense). It is generally represented by one number for each axis in a Cartesian coordinate system. A vector specifies a magnitude and direction, in a space of any dimension. It is often represented by a point which would be reached by moving from the origin in the direction and by the amount of the magnitude of the vector. It can also be represented as a magnitude and however many angles are required for the dimensionality of the space (1 angle in 2D, 2 angles in 3D, etc). It is important to remember that the vector is not inherently associated with any particular point. In computer graphics, when transforming an object (like a polygon) the vectors (like surface normals) transform differently because translation is irrelevant, although rotate and scale are not. What was the question? :-) Sam Uselton uselton@nas.nasa.gov employed by MRJ working for NASA (Ames) sepaking for myself
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Path: arc1-ca.pugleaf.net!cnn.nas.nasa.gov!news From: uselton@wk309.nas.nasa.gov (Samuel P. Uselton) Newsgroups: comp.graphics.algorithms,comp.os.ms-windows.programmer.graphics,comp.sys.amiga.graphics Subject: Re: 3d programming Followup-To: comp.graphics.algorithms Date: 23 Feb 1996 10:45:02 -0800 Organization: MRJ at NASA Ames Sender: uselton@wk309.nas.nasa.gov Message-ID: <x4opwb5c24x.fsf@wk309.nas.nasa.gov> References: <4g63cj$p42@news.sdsmt.edu> Reply-To: uselton@nas.nasa.gov NNTP-Posting-Host: wk309.nas.nasa.gov In-reply-to: kbs3387@silver.sdsmt.edu's message of 18 Feb 1996 02:37:07 GMT X-Newsreader: Gnus v5.1