Subversion Repositories planix.SVN

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

static double v3,u2,u3,a,b; /*v=view,p=obj,u=unit.y*/

static int
Xharrison(struct place *place, double *x, double *y)
{
        double p1 = -place->nlat.c*place->wlon.s;
        double p2 = -place->nlat.c*place->wlon.c;
        double p3 = place->nlat.s;
        double d = b + u3*p2 - u2*p3;
        double t;
        if(d < .01)
                return -1;
        t = a/d;
        if(v3*place->nlat.s < 1.)
                return -1;
        *y = t*p2*u2 + (v3-t*(v3-p3))*u3;
        *x = t*p1;
        if(t < 0)
                return 0;
        if(*x * *x + *y * *y > 16)
                return -1;
        return 1;
}

proj
harrison(double r, double alpha)
{
        u2 = cos(alpha*RAD);
        u3 = sin(alpha*RAD);
        v3 = r;
        b = r*u2;
        a = 1 + b;
        if(r<1.001 || a<sqrt(r*r-1))
                return 0;
        return Xharrison;
}