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#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;
}
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