| #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; | |
| } |