CSSTRID(3NCARG)

💖 CSSTRID — the Delaunay-triangulation-on-a-sphere girlie 💖

okay so bestie, welcome to the NCAR GRAPHICS corner of the manual pages 🎀. Today's main character is CSSTRID, and she's here to serve you a whole Delaunay triangulation of points scattered across a sphere. No cap, it's giving computational geometry but make it ✨cute✨. Grab a strawberry 🍓, sit down, and let's get into it.

✨ NAME ✨

CSSTRID — calculates a Delaunay triangulation for data on a sphere 🦋

🌸 SYNOPSIS 🌸

CALL CSSTRID (N, RLAT, RLON, NT, NTRI, IWK, RWK, IER)

like, that's the whole summoning ritual. say it with your chest 💅

👑 DESCRIPTION 👑

okay here's the cast of characters, one by one, no skipping, we don't do that here 🫶

• N (integer, input) — the number of input data points. And it's gotta be N > 2, because triangulating two points is not a vibe, bestie, you literally cannot.
• RLAT (double precision, input) — an array holding the latitudes of the input data, expressed in degrees. ⚠️ Important lore: the first three points must not be collinear, meaning they cannot lie on a common great circle. If they do? That's a problem, and we don't do problems. 😭
• RLON (double precision, input) — an array holding the longitudes of the input data, also expressed in degrees. Yes it's a separate array, yes you need both, that's just the lore. 🌍
• NT (integer, output) — the number of triangles in the triangulation! 🎉 Except—plot twist—if IER .NE. 0, then NT = 0. The math of it, where NB is the number of boundary points on the convex hull of the data: if NB .GE. 3, then NT = 2N-NB-2; otherwise NT = 2N-4. The input data are considered to be bounded if they all lie in one hemisphere. And honestly? Dimensioning NT for 2*N will always work. always. slay. 💅
• NTRI (integer, output) — a two-dimensional integer array dimensioned for 3 x NT, where NT is the number of triangles in the triangulation (NT is at most 2*N). NTRI contains the triangulation data. The vertices of the Kth triangle are:

(PLAT(NTRI((1,K)),PLON(NTRI(1,K)),
(PLAT(NTRI((2,K)),PLON(NTRI(2,K)),
(PLAT(NTRI((3,K)),PLON(NTRI(3,K))

yeah we're just gonna let that sit there exactly as it is, iconic behavior, no notes 🔥

• IWK (integer, input) — an integer workspace of length 27*N. yes, twenty-seven times N. she needs room to think. 🧠
• RWK (double precision, input) — a work array dimensioned for 13*N. 📌 And listen: this work array must be typed DOUBLE PRECISION. Do not come in here with single precision, I am begging you. 🙈
• IER (integer, output) — the error return value! If IER comes back as 0, then no errors were detected, we love a clean run, we love a flawless serve ✨. If IER is non-zero, then go refer to the man page for cssgrid_errors for the details — she will tell you exactly what went wrong, iykyk.

🦋 USAGE 🦋

CSSTRID is called to find a Delaunay triangulation of data randomly positioned on the surface of a sphere. 🌐 And the tea: CSSTRID is a double precision version of CSSTRI. So if you're out here wanting the double-precision experience, you're in the right place, bestie. 💜

🌈 ACCESS 🌈

To use CSSTRID, load the NCAR Graphics library ngmath. that's it, that's the whole access requirement, periodt. 👑

🎀 SEE ALSO 🎀

• css_overview
• cssgrid
• csstri
• csvoro

Complete documentation for Cssgrid is available at URL http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html 🌸

💖 COPYRIGHT 💖

Copyright (C) 2000 University Corporation for Atmospheric Research

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

fr fr, read the license, bestie, it's the rules. 🫶

and that's the whole page!! 💅 NCAR Graphics girlies stay winning, this one dropped back in May 2000 and she's still serving CSSTRID(3NCARG) energy to this very day. go forth, triangulate your sphere, and remember: double precision work arrays only. mwah 🎀✨🦋