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