Article View: comp.graphics.algorithms
Article #50Re: BSP tree question
From: Jim Mazrimas
Date: Fri, 01 Sep 1995 07:02
Date: Fri, 01 Sep 1995 07:02
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1256 bytes
Tim Wendt (tim.wendt@daytonoh.ncr.com) wrote:
> What is the test to determine if a vector is is front or behind the partition
> vector (2D only ala Doom) when building a BSP tree?
> Tim
> --------------------------------------------------------
> | "Hmm...beer!" - Homer Simpson
> ---tim.wendt@daytonoh.attgis.com---------A1200/030/33---
The cross product. Cross(V,W) is positive if vector V is "to the
right" of vector W. Negative otherwise. In 2D, the cross prod is the
the determinant of the matrix made up by the two vectors:
Cross(V,W) = |V1 V2| = V1 * W2 - V2 * W1
|W1 W2|
Hope this helps.
Jim
mazrimas@shell.portal.com
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Path: arc1-ca.pugleaf.net!jobe.shell.portal.com!mazrimas From: mazrimas@shell.portal.com (Jim Mazrimas) Newsgroups: comp.graphics.algorithms,comp.sys.amiga.programmer,rec.games.programmer Subject: Re: BSP tree question Followup-To: comp.graphics.algorithms,comp.sys.amiga.programmer,rec.games.programmer Date: 1 Sep 1995 07:02:10 GMT Organization: Portal Communications Company -- 408/973-9111 (voice) 408/973-8091 (data) Message-ID: <426b5i$9ll@news1.shell> References: <DE70Io.AG6@corsair.daytonoh.attgis.com> NNTP-Posting-Host: jobe.shell.portal.com X-Newsreader: TIN [version 1.2 PL2]