122 lines
2.2 KiB
C
122 lines
2.2 KiB
C
#include <u.h>
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#include <libc.h>
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#include "map.h"
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#define BIG 1.e15
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#define HFUZZ .0001
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static double hcut[3] ;
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static double kr[3] = { .5, -1., .5 };
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static double ki[3] = { -1., 0., 1. }; /*to multiply by sqrt(3)/2*/
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static double cr[3];
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static double ci[3];
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static struct place hem;
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static struct coord twist;
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static double rootroot3, hkc;
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static double w2;
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static double rootk;
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static void
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reflect(int i, double wr, double wi, double *x, double *y)
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{
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double pr,pi,l;
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pr = cr[i]-wr;
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pi = ci[i]-wi;
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l = 2*(kr[i]*pr + ki[i]*pi);
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*x = wr + l*kr[i];
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*y = wi + l*ki[i];
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}
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static int
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Xhex(struct place *place, double *x, double *y)
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{
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int ns;
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int i;
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double zr,zi;
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double sr,si,tr,ti,ur,ui,vr,vi,yr,yi;
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struct place p;
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copyplace(place,&p);
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ns = place->nlat.l >= 0;
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if(!ns) {
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p.nlat.l = -p.nlat.l;
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p.nlat.s = -p.nlat.s;
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}
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if(p.nlat.l<HFUZZ) {
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for(i=0;i<3;i++)
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if(fabs(reduce(p.wlon.l-hcut[i]))<HFUZZ) {
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if(i==2) {
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*x = 2*cr[0] - cr[1];
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*y = 0;
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} else {
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*x = cr[1];
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*y = 2*ci[2*i];
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}
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return(1);
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}
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p.nlat.l = HFUZZ;
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sincos(&p.nlat);
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}
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norm(&p,&hem,&twist);
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Xstereographic(&p,&zr,&zi);
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zr /= 2;
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zi /= 2;
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cdiv(1-zr,-zi,1+zr,zi,&sr,&si);
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csq(sr,si,&tr,&ti);
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ccubrt(1+3*tr,3*ti,&ur,&ui);
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csqrt(ur-1,ui,&vr,&vi);
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cdiv(rootroot3+vr,vi,rootroot3-vr,-vi,&yr,&yi);
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yr /= rootk;
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yi /= rootk;
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elco2(fabs(yr),yi,hkc,1.,1.,x,y);
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if(yr < 0)
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*x = w2 - *x;
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if(!ns) reflect(hcut[0]>place->wlon.l?0:
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hcut[1]>=place->wlon.l?1:
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2,*x,*y,x,y);
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return(1);
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}
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proj
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hex(void)
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{
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int i;
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double t;
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double root3;
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double c,d;
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struct place p;
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hcut[2] = PI;
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hcut[1] = hcut[2]/3;
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hcut[0] = -hcut[1];
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root3 = sqrt(3.);
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rootroot3 = sqrt(root3);
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t = 15 -8*root3;
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hkc = t*(1-sqrt(1-1/(t*t)));
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elco2(BIG,0.,hkc,1.,1.,&w2,&t);
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w2 *= 2;
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rootk = sqrt(hkc);
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latlon(90.,90.,&hem);
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latlon(90.,0.,&p);
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Xhex(&p,&c,&t);
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latlon(0.,0.,&p);
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Xhex(&p,&d,&t);
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for(i=0;i<3;i++) {
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ki[i] *= root3/2;
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cr[i] = c + (c-d)*kr[i];
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ci[i] = (c-d)*ki[i];
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}
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deg2rad(0.,&twist);
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return(Xhex);
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}
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int
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hexcut(struct place *g, struct place *og, double *cutlon)
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{
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int t,i;
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if(g->nlat.l>=-HFUZZ&&og->nlat.l>=-HFUZZ)
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return(1);
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for(i=0;i<3;i++) {
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t = ckcut(g,og,*cutlon=hcut[i]);
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if(t!=1) return(t);
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}
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return(1);
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}
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