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Annotation of researchv10no/cmd/map/libmap/harrison.c, revision 1.1.1.1

1.1       root        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: }

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