lwpoly_construct_circle()

LWPOLY * lwpoly_construct_circle ( int32_t  srid, double  x, double  y, double  radius, uint32_t  segments_per_quarter, char  exterior  )

extern

Definition at line 120 of file lwpoly.c.

{
        const uint32_t segments = 4*segments_per_quarter;
        double theta;
        LWPOLY *lwpoly;
        POINTARRAY *pa;
        POINT4D pt;
        uint32_t i;
 
        if (segments_per_quarter == 0)
        {
                lwerror("Need at least one segment per quarter-circle.");
                return NULL;
        }
 
        if (radius < 0)
        {
                lwerror("Radius must be positive.");
                return NULL;
        }
 
        theta = 2*M_PI / segments;
 
        lwpoly = lwpoly_construct_empty(srid, LW_FALSE, LW_FALSE);
        pa = ptarray_construct_empty(LW_FALSE, LW_FALSE, segments + 1);
 
        if (exterior)
                radius *= sqrt(1 + pow(tan(theta/2), 2));
 
        for (i = 0; i <= segments; i++)
        {
                pt.x = x + radius*sin(i * theta);
                pt.y = y + radius*cos(i * theta);
                ptarray_append_point(pa, &pt, LW_TRUE);
        }
 
        lwpoly_add_ring(lwpoly, pa);
        return lwpoly;
}

References LW_FALSE, LW_TRUE, lwerror(), lwpoly_add_ring(), lwpoly_construct_empty(), ptarray_append_point(), ptarray_construct_empty(), POINT4D::x, and POINT4D::y.

Referenced by ST_MinimumBoundingCircle(), and test_lwpoly_construct_circle().

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