From: "Jan Simon" <>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Calculate whether a point is above or below a plane
Date: Mon, 12 Jul 2010 18:59:06 +0000 (UTC)
Organization: Universit&#228;t Heidelberg
Lines: 6
Message-ID: <i1folq$9m9$>
References: <i1bqu5$ig2$> <i1cloo$s4h$> <i1fkkr$g8p$>
Reply-To: "Jan Simon" <>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
X-Trace: 1278961146 9929 (12 Jul 2010 18:59:06 GMT)
NNTP-Posting-Date: Mon, 12 Jul 2010 18:59:06 +0000 (UTC)
X-Newsreader: MATLAB Central Newsreader 869888
Xref: comp.soft-sys.matlab:652458

Dear Ian,

If you have 50k points, you can rotate the 3D coordinates such that the normal vektor of the plane is parallel e.g. to the Z-axis.
Then a simple >= operation of the Z-component of the points is enough to decide if they are over or under the plane.