41 lines
708 B
C
41 lines
708 B
C
#include <u.h>
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#include <libc.h>
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#include "map.h"
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static double v3,u2,u3,a,b; /*v=view,p=obj,u=unit.y*/
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static int
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Xharrison(struct place *place, double *x, double *y)
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{
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double p1 = -place->nlat.c*place->wlon.s;
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double p2 = -place->nlat.c*place->wlon.c;
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double p3 = place->nlat.s;
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double d = b + u3*p2 - u2*p3;
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double t;
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if(d < .01)
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return -1;
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t = a/d;
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if(v3*place->nlat.s < 1.)
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return -1;
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*y = t*p2*u2 + (v3-t*(v3-p3))*u3;
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*x = t*p1;
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if(t < 0)
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return 0;
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if(*x * *x + *y * *y > 16)
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return -1;
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return 1;
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}
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proj
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harrison(double r, double alpha)
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{
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u2 = cos(alpha*RAD);
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u3 = sin(alpha*RAD);
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v3 = r;
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b = r*u2;
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a = 1 + b;
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if(r<1.001 || a<sqrt(r*r-1))
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return 0;
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return Xharrison;
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}
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