subroutine aptcirp (ax, ay, az, bx, by, bz, cx, cy, cz, np, tol, & px, py, pz, ux, uy, uz, rad, nerr) ccbeg. cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c SUBROUTINE APTCIRP c c call aptcirp (ax, ay, az, bx, by, bz, cx, cy, cz, np, tol, c & px, py, pz, ux, uy, uz, rad, nerr) c c Version: aptcirp Updated 1993 June 20 17:20. c aptcirp Originated 1993 April 27, 14:40. c c Author: Arthur L. Edwards, LLNL, L-298, Telephone (925) 422-4123. c c c Purpose: For each of the np sets of 3 points a = (ax, ay, az), c b = (bx, by, bz) and c = (cx, cy, cz), to find the center c p = (px, py, pz), unit normal vector u = (ux, uy, uz) and c radius rad of the circle through points (a, b, c). c Flag nerr indicates any input error, if not zero. c c Method: Point "p" is in the planes bisecting vectors "ab" and "ac", and c is coplanar with points (a, b, c): c (p - 0.5 * (b + a)) dot (b - a) = 0 c (p - 0.5 * (c + a)) dot (c - a) = 0 c (p - a) dot ((b - a) X (c - a)) = 0 c These 3 equations are solved for px, py and pz. c c Input: ax, ay, az, bx, by, bz, cx, cy, cz, np, tol. c c Output: px, py, pz, ux, uy, uz, rad, nerr. c c Calls: aptvpln, aptvdis, aptvsum, aptvdot, aptsolv, aptvuna c c c History: 1994 June 20. Changed output vector "u" = (ux, uy, uz) to c a unit vector, as originally intended. c c Glossary: c c ax,ay,az Input The x, y, z coordinates of point "a". Size np. c c bx,by,bz Input The x, y, z coordinates of point "b". Size np. c c cx,cy,cz Input The x, y, z coordinates of point "c". Size np. c c nerr Output Indicates an input error, if not 0. c 1 if np is not positive. c c np Input The number of sets of points (a, b, c) for which the c circle is to be found. Must be positive. c c px,py,pz Output The x, y, z coordinates of the center of the circle. c Each 1.e99 if the points (a, b, c) are colinear or c congruent. Size np. c c rad Output The radius of the circle, larger than 1.e99 if the c points (a, b, c) are colinear or congruent. Size np. c c tol Input Numerical tolerance limit. c On Cray computers, recommend 1.e-5 to 1.e-11. c c ux,uy,uz Output The x, y, z components of unit vector "u", normal to c the plane of the circle. Each zero if points c (a, b, c) are colinear or congruent. Size np. c cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc ccend. c.... Dimensioned arguments. c---- Coordinate x of input point "a". dimension ax (1) c---- Coordinate y of input point "a". dimension ay (1) c---- Coordinate z of input point "a". dimension az (1) c---- Coordinate x of input point "b". dimension bx (1) c---- Coordinate y of input point "b". dimension by (1) c---- Coordinate z of input point "b". dimension bz (1) c---- Coordinate x of input point "c". dimension cx (1) c---- Coordinate y of input point "c". dimension cy (1) c---- Coordinate z of input point "c". dimension cz (1) c---- Coordinate x of center of circle "p". dimension px (1) c---- Coordinate y of center of circle "p". dimension py (1) c---- Coordinate z of center of circle "p". dimension pz (1) c---- Radius of circle. dimension rad (1) c---- Component x of normal vector "u". dimension ux (1) c---- Component y of normal vector "u". dimension uy (1) c---- Component z of normal vector "u". dimension uz (1) c.... Local variables. Floating point. c---- Coefficients of equations for "p". common /laptcirp/ a (3,3) c---- Dot product of "ab" and "abmid". common /laptcirp/ abdot (64) c---- Length of vector "abmid". common /laptcirp/ abmidl (64) c---- Component x of vector "abmid". common /laptcirp/ abmidx (64) c---- Component y of vector "abmid". common /laptcirp/ abmidy (64) c---- Component z of vector "abmid". common /laptcirp/ abmidz (64) c---- Length of vector "ab". common /laptcirp/ abvlen (64) c---- Component x of vector "ab". common /laptcirp/ abx (64) c---- Component y of vector "ab". common /laptcirp/ aby (64) c---- Component z of vector "ab". common /laptcirp/ abz (64) c---- Dot product of "ac" and "acmid". common /laptcirp/ acdot (64) c---- Length of vector "acmid". common /laptcirp/ acmidl (64) c---- Component x of vector "acmid". common /laptcirp/ acmidx (64) c---- Component y of vector "acmid". common /laptcirp/ acmidy (64) c---- Component z of vector "acmid". common /laptcirp/ acmidz (64) c---- Length of vector "ac". common /laptcirp/ acvlen (64) c---- Component x of vector "ac". common /laptcirp/ acx (64) c---- Component y of vector "ac". common /laptcirp/ acy (64) c---- Component z of vector "ac". common /laptcirp/ acz (64) c---- Dot product of "a" and "u". common /laptcirp/ audot (64) c---- Inverse of matrix a. common /laptcirp/ b (3,3) c---- A big number. common /laptcirp/ big c---- Solution for "p". common /laptcirp/ q (3) c---- Solution for "p" (check). common /laptcirp/ qm (3) c---- Residuals for "p" (check). common /laptcirp/ qr (3) c---- Right side of equations for "p". common /laptcirp/ s (3) c---- Right side of equations for "p" (check). common /laptcirp/ sm (3) c---- Residuals of right side of equations for "p" (check). common /laptcirp/ sr (3) c---- Working memory for aptsolv. common /laptcirp/ w (3,4) c.... Local variables. Integers. c---- Index in arrays. common /laptcirp/ n c---- First index of subset of data. common /laptcirp/ n1 c---- Last index of subset of data. common /laptcirp/ n2 c---- Index in external array. common /laptcirp/ nn c---- Size of current subset of data. common /laptcirp/ ns c---- Twice area of triangle (a, b, c). common /laptcirp/ vlen (64) cbugc***DEBUG begins. cbug 9901 format (/ 'aptcirp finding circle through points:' / cbug & (i3,' ax,ay,az=',1p3e22.14 / cbug & ' bx,by,bz=',1p3e22.14 / cbug & ' cx,cy,cz=',1p3e22.14)) cbug write ( 3, 9901) (n, ax(n), ay(n), az(n), bx(n), by(n), bz(n), cbug & cx(n), cy(n), cz(n), n = 1, np) cbugc***DEBUG ends. c.... Initialize. big = 1.e99 nerr = 0 c.... Test for input errors. if (np .le. 0) then nerr = 1 go to 210 endif c.... Set up the indices of the first subset of data. n1 = 1 n2 = min (np, 64) c.... Loop over subsets of data. 110 ns = n2 - n1 + 1 c.... Find the vectors normal to the plane of each circle. call aptvpln (ax(n1), ay(n1), az(n1), bx(n1), by(n1), bz(n1), & cx(n1), cy(n1), cz(n1), ns, tol, & ux(n1), uy(n1), uz(n1), vlen, nerr) c.... Find the difference vectors "ab" and "ac". call aptvdis (ax(n1), ay(n1), az(n1), bx(n1), by(n1), bz(n1), ns, & tol, abx, aby, abz, abvlen, nerr) call aptvdis (ax(n1), ay(n1), az(n1), cx(n1), cy(n1), cz(n1), ns, & tol, acx, acy, acz, acvlen, nerr) c.... Find the midpoint vectors "abmid" and "acmid". call aptvsum (0, 0.5, ax(n1), ay(n1), az(n1), & 0.5, bx(n1), by(n1), bz(n1), ns, tol, & abmidx, abmidy, abmidz, abmidl, nerr) call aptvsum (0, 0.5, ax(n1), ay(n1), az(n1), & 0.5, cx(n1), cy(n1), cz(n1), ns, tol, & acmidx, acmidy, acmidz, acmidl, nerr) c.... Find the vector dot products ab.abmid, ac.acmid and a.u. call aptvdot (abx, aby, abz, abmidx, abmidy, abmidz, ns, tol, & abdot, nerr) call aptvdot (acx, acy, acz, acmidx, acmidy, acmidz, ns, tol, & acdot, nerr) call aptvdot (ax(n1), ay(n1), az(n1), ux(n1), uy(n1), uz(n1), ns, & tol, audot, nerr) c.... Find the center of each circle. do 120 n = 1, ns nn = n1 + n - 1 a(1,1) = abx(n) a(1,2) = aby(n) a(1,3) = abz(n) a(2,1) = acx(n) a(2,2) = acy(n) a(2,3) = acz(n) a(3,1) = ux (nn) a(3,2) = uy (nn) a(3,3) = uz (nn) s(1) = abdot(n) s(2) = acdot(n) s(3) = audot(n) call aptsolv (a, s, 3, w, 3, tol, q, b, qm, qr, sm, sr, nerr) px(nn) = q(1) py(nn) = q(2) pz(nn) = q(3) c.... Test for colinear or congruent points (a, b, c). if (nerr .eq. 1) then px(nn) = big py(nn) = big pz(nn) = big nerr = 0 endif 120 continue c.... Find the radius of each circle. call aptvdis (ax(n1), ay(n1), az(n1), px(n1), py(n1), pz(n1), ns, & tol, abx, aby, abz, rad(n1), nerr) c.... Find the unit normal vectors. call aptvuna (ux(n1), uy(n1), uz(n1), ns, tol, vlen, nerr) c.... See if all data subsets are done. c---- Do another subset of data. if (n2 .lt. np) then n1 = n2 + 1 n2 = min (np, n1 + 63) go to 110 endif cbugc***DEBUG begins. cbug 9902 format (/ 'aptcirp results:' / cbug & (i3,' px,py,pz=',1p3e22.14 / cbug & ' ux,uy,uz=',1p3e22.14 / cbug & ' rad= ',1pe22.14)) cbug write ( 3, 9902) (n, px(n), py(n), pz(n), cbug & ux(n), uy(n), uz(n), rad(n), n = 1, np) cbugc***DEBUG ends. 210 return c.... End of subroutine aptcirp. (+1 line.) end UCRL-WEB-209832