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Annotation of researchv8dc/cmd/map/libmap/perspective.c, revision 1.1.1.1

1.1       root        1: #include "map.h"
                      2: 
                      3: float viewpt;
                      4: 
                      5: Xperspective(p, x, y)
                      6: struct place *p;
                      7: float *x, *y;
                      8: {
                      9:        float r;
                     10:        if(viewpt<=1. && p->nlat.s<=viewpt+.01)
                     11:                return(-1);
                     12:        r = p->nlat.c*(viewpt - 1.)/(viewpt - p->nlat.s);
                     13:        *x = - r*p->wlon.s;
                     14:        *y = - r*p->wlon.c;
                     15:        if(r>4.)
                     16:                return(0);
                     17:        if(fabs(viewpt)>1. && p->nlat.s<=1./viewpt)
                     18:                return(0);
                     19:        return(1);
                     20: }
                     21: 
                     22: Xstereographic(p, x, y)
                     23: struct place *p;
                     24: float *x, *y;
                     25: {
                     26:        viewpt = -1;
                     27:        return(Xperspective(p, x, y));
                     28: }
                     29: 
                     30: int (*perspective(radius))()
                     31: float radius;
                     32: {
                     33:        extern Xorthographic();
                     34:        viewpt = radius;
                     35:        if(radius>=1000.)
                     36:                return(Xorthographic);
                     37:        if(fabs(radius-1.)<.0001)
                     38:                exit(1);
                     39:        return(Xperspective);
                     40: }
                     41: 
                     42: int (*stereographic())()
                     43: {
                     44:        viewpt = -1.;
                     45:        return(Xperspective);
                     46: }
                     47: 
                     48: int (*gnomonic())()
                     49: {
                     50:        viewpt = 0.;
                     51:        return(Xperspective);
                     52: }

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