c_csstrid(3NCARG)

✨ c_csstrid — bestie, let's triangulate a SPHERE 💅

okay so this is a page from the NCAR GRAPHICS manual, section 3NCARG, and it's all about c_csstrid — the girlies who calculate a Delaunay triangulation for data on a sphere. yes, a sphere. we're doing geometry in 3D today, no cap 🌍✨

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🎀 NAME 🎀

c_csstrid — calculates a Delaunay triangulation for data on a sphere. that's it, that's the whole job, and she does it flawlessly 💖

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🦋 FUNCTION PROTOTYPE 🦋

int *c_csstrid(int, double [], double [], int *, int *);

look at her. iconic signature. int * return type, meaning she hands you back a pointer and you better treat it right 🫶

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🌸 SYNOPSIS 🌸

int *c_csstrid(n, rlat, rlon, nt, ier);

five args, one dream. let's break them down bestie ⬇️

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✨ DESCRIPTION ✨

• n — the number of input data points, and the vibe check here is n > 2. literally you need more than two points, that's non-negotiable 💀
• rlat — an array holding the latitudes of your input data, expressed in degrees. ⚠️ important: the first three points must not be collinear — as in, they can't all lie on a common great circle. don't do it. she will not be happy.
• rlon — an array holding the longitudes of your input data, also in degrees. matching set with rlat, as she should 💅
• nt — *nt is the number of triangles in the triangulation… UNLESS *ier is non-zero, in which case *nt = 0 (sad girl hours 😭). now let nb be the number of boundary points on the convex hull of the data. if nb is greater than 3, then *nt = 2n-nb-2. otherwise *nt = 2n-4. and for the record, the input data are considered to be bounded if they all lie in one hemisphere 🌐
• ier — the error return value. if *ier comes back as 0, then no errors were detected and we are thriving ✨. if *ier is non-zero, then bestie… go refer to the error list in cssgrid_errors for the details. she's telling you something. listen. 🙈

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💖 USAGE 💖

you call c_csstrid to find a Delaunay triangulation of data randomly positioned on the surface of a sphere. that's the whole point, that's her main character moment 👑

also, tea: c_csstrid is the double precision version of c_csstri. same energy, more precision, periodt 💅

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🔥 RETURN VALUE 🔥

c_csstrid returns a pointer to a linear array that contains a sequence of integer triples. each element of a triple is an index of a vertex of a triangle, and each index references an original data point as it occurs in sequence in the input data set. ⚠️ numbering starts at 0 — zero-indexed girlies rise up 🫶

so like, if the triple <5,0,2> were in the list of triples, then (rlat[5],rlon[5]), (rlat[0],rlon[0]), and (rlat[2],rlon[2]) would be vertices of a triangle in the Delaunay triangulation. see how that works? chef's kiss 🤌

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🌈 ACCESS 🌈

to use c_csstrid, load the NCAR Graphics library ngmath. that's the one. don't forget it or she simply will not run 💀

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💜 SEE ALSO 💜

• css_overview
• c_cssgrid
• c_csstri
• cssgrid_errors

complete documentation for Cssgrid is available at URL

http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html

go read it, iykyk 📚✨

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👑 COPYRIGHT 👑

Copyright (C) 2000 University Corporation for Atmospheric Research

The use of this Software is governed by a License Agreement.

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okay that's the whole page bestie, you're officially a sphere-triangulation girly now 🧚💖 go forth and Delaunay

this lil masterpiece dropped as part of UNIX, back in May 2000, from the NCAR GRAPHICS source — vintage but make it slay 🎀💅✨