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