Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!news.albasani.net!news2.arglkargh.de!news.musoftware.de!wum.musoftware.de!fu-berlin.de!uni-berlin.de!news.dfncis.de!not-for-mail From: =?ISO-8859-1?Q?Hans-Bernhard_Br=F6ker?= Newsgroups: comp.graphics.apps.gnuplot Subject: Re: Can contour surface model be saved to file? Date: Tue, 21 Jun 2011 00:12:52 +0200 Lines: 15 Message-ID: <969uv3F8k8U1@mid.dfncis.de> References: <5fcfa1fb-f678-4d88-887e-57fa4303df99@b3g2000vbm.googlegroups.com> <961o1dFmv7U1@mid.dfncis.de> <966dnbFp3rU1@mid.dfncis.de> <967126Ff39U1@mid.individual.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: news.dfncis.de ekZ/LyqQR+cVCC5v4sQgTw0MSPCtJuHC0Vpj7+0080GJKFDSKDPYaLsEJq Cancel-Lock: sha1:6Xrerwm4mP8X4JSZwERlhLy8f5E= User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 In-Reply-To: <967126Ff39U1@mid.individual.net> Xref: x330-a1.tempe.blueboxinc.net comp.graphics.apps.gnuplot:390 On 19.06.2011 21:30, Ingo Thies wrote: > One technical question at this point: How are the contours actually > calculated in gnuplot? Like I roughly described in my post 3 days ago. First, you need a grid dataset. This is triangulated by adding diagonals, and then we run "Marching Triangles" on the triangular mesh. It looks for edges in the triangulation that go from above to below the contour plane. Linear interpolation yields a point on each such edge where it can be assumed to cut through the contour plane. Connect these dots triangle by triangle until you either hit a dataset boundary or find a complete cycle. Repeat until all straddling edges are accounted for. Repeat for all contour levels.