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

1.1       root        1: #include "map.h"
                      2: 
                      3: /* christmas wreath projection, 1989 card.
                      4:    wreath par1 par2
                      5:    par1 is fraction of full circle the wreath is to cover
                      6:        (the gap is where you put the bow)
                      7:    par2 tells how deeply to curve the meridians, about .2 - .5
                      8:    inner radius is 1-a, equatorial is 1, outer is 1+a
                      9:    
                     10:    fudging for beauty: shift things south 30 degrees so
                     11:    equator is really not at radius 1, and stretch northern
                     12:    hemisphere quadratically away from the equator
                     13: */
                     14: static double a = .7, b, c;
                     15: int squinge;
                     16: 
                     17: static int (*Xcylequalarea)(struct place *, double *, double *);
                     18: 
                     19: static int
                     20: Xwreath(struct place *place, double *x, double *y)
                     21: {
                     22:        double xx, yy, r, h, theta;
                     23:        struct place nplace;
                     24:        double l;
                     25:        nplace = *place;
                     26:        if(squinge) {
                     27:                if(nplace.nlat.l < 0)
                     28:                        nplace.nlat.l -= PI/6-FUZZ;
                     29:                else {
                     30:                        l = nplace.nlat.l;
                     31:                        nplace.nlat.l = -PI/6 + l + 2*l*l/(3*PI);
                     32:                }
                     33:                if(nplace.nlat.l < -PI/2)
                     34:                        return 0;
                     35:                sincos(&nplace.nlat);
                     36:        }
                     37:        Xcylequalarea(&nplace, &xx, &yy);
                     38:        r = 1 - a*yy;
                     39:        theta = b*xx;
                     40:        h = c*sin(theta)*sqrt(1-yy*yy);
                     41:        theta += h/r;
                     42:        *y = -r*cos(theta);
                     43:        *x = r*sin(theta);
                     44:        return(1);
                     45: }
                     46: 
                     47: proj
                     48: wreath(double par1, double par2)
                     49: {
                     50:        Xcylequalarea = cylequalarea(45.);
                     51:        b = fabs(par1);
                     52:        c = par2;
                     53:        squinge = par1<0;
                     54:        return Xwreath;
                     55: }

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