Subversion Repositories planix.SVN

#include <u.h>
#include <libc.h>
#include "map.h"

#define BIG 1.e15
#define HFUZZ .0001

static double hcut[3] ;
static double kr[3] = { .5, -1., .5 };
static double ki[3] = { -1., 0., 1. };  /*to multiply by sqrt(3)/2*/
static double cr[3];
static double ci[3];
static struct place hem;
static struct coord twist;
static double  rootroot3, hkc;
static double w2;
static double rootk;

static void
reflect(int i, double wr, double wi, double *x, double *y)
{
        double pr,pi,l;
        pr = cr[i]-wr;
        pi = ci[i]-wi;
        l = 2*(kr[i]*pr + ki[i]*pi);
        *x = wr + l*kr[i];
        *y = wi + l*ki[i];
}

static int
Xhex(struct place *place, double *x, double *y)
{
        int ns;
        register i;
        double zr,zi;
        double sr,si,tr,ti,ur,ui,vr,vi,yr,yi;
        struct place p;
        copyplace(place,&p);
        ns = place->nlat.l >= 0;
        if(!ns) {
                p.nlat.l = -p.nlat.l;
                p.nlat.s = -p.nlat.s;
        }
        if(p.nlat.l<HFUZZ) {
                for(i=0;i<3;i++)
                        if(fabs(reduce(p.wlon.l-hcut[i]))<HFUZZ) {
                                if(i==2) {
                                        *x = 2*cr[0] - cr[1];
                                        *y = 0;
                                } else {
                                        *x = cr[1];
                                        *y = 2*ci[2*i];
                                }
                                return(1);
                        }
                p.nlat.l = HFUZZ;
                sincos(&p.nlat);
        }
        norm(&p,&hem,&twist);
        Xstereographic(&p,&zr,&zi);
        zr /= 2;
        zi /= 2;
        cdiv(1-zr,-zi,1+zr,zi,&sr,&si);
        csq(sr,si,&tr,&ti);
        ccubrt(1+3*tr,3*ti,&ur,&ui);
        csqrt(ur-1,ui,&vr,&vi);
        cdiv(rootroot3+vr,vi,rootroot3-vr,-vi,&yr,&yi);
        yr /= rootk;
        yi /= rootk;
        elco2(fabs(yr),yi,hkc,1.,1.,x,y);
        if(yr < 0)
                *x = w2 - *x;
        if(!ns) reflect(hcut[0]>place->wlon.l?0:
                        hcut[1]>=place->wlon.l?1:
                        2,*x,*y,x,y);
        return(1);
}

proj
hex(void)
{
        register i;
        double t;
        double root3;
        double c,d;
        struct place p;
        hcut[2] = PI;
        hcut[1] = hcut[2]/3;
        hcut[0] = -hcut[1];
        root3 = sqrt(3.);
        rootroot3 = sqrt(root3);
        t = 15 -8*root3;
        hkc = t*(1-sqrt(1-1/(t*t)));
        elco2(BIG,0.,hkc,1.,1.,&w2,&t);
        w2 *= 2;
        rootk = sqrt(hkc);
        latlon(90.,90.,&hem);
        latlon(90.,0.,&p);
        Xhex(&p,&c,&t);
        latlon(0.,0.,&p);
        Xhex(&p,&d,&t);
        for(i=0;i<3;i++) {
                ki[i] *= root3/2;
                cr[i] = c + (c-d)*kr[i];
                ci[i] = (c-d)*ki[i];
        }
        deg2rad(0.,&twist);
        return(Xhex);
}

int
hexcut(struct place *g, struct place *og, double *cutlon)
{
        int t,i;
        if(g->nlat.l>=-HFUZZ&&og->nlat.l>=-HFUZZ)
                return(1);
        for(i=0;i<3;i++) {
                t = ckcut(g,og,*cutlon=hcut[i]);
                if(t!=1) return(t);
        }
        return(1);
}