1 #include "map.h" 2 3 static double v3,u2,u3,a,b; /*v=view,p=obj,u=unit.y*/ 4 5 static int 6 Xharrison(struct place *place, double *x, double *y) 7 { 8 double p1 = -place->nlat.c*place->wlon.s; 9 double p2 = -place->nlat.c*place->wlon.c; 10 double p3 = place->nlat.s; 11 double d = b + u3*p2 - u2*p3; 12 double t; 13 if(d < .01) 14 return -1; 15 t = a/d; 16 if(v3*place->nlat.s < 1.) 17 return -1; 18 *y = t*p2*u2 + (v3-t*(v3-p3))*u3; 19 *x = t*p1; 20 if(t < 0) 21 return 0; 22 if(*x * *x + *y * *y > 16) 23 return -1; 24 return 1; 25 } 26 27 proj 28 harrison(double r, double alpha) 29 { 30 u2 = cos(alpha*RAD); 31 u3 = sin(alpha*RAD); 32 v3 = r; 33 b = r*u2; 34 a = 1 + b; 35 if(r<1.001 || a<sqrt(r*r-1)) 36 return 0; 37 return Xharrison; 38 } 39