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;

}