ptarray_closest_segment_2d()

int ptarray_closest_segment_2d	(	const POINTARRAY *	pa,
		const POINT2D *	qp,
		double *	dist
	)

Parameters

pa	the subject pointarray
qp	the query point
dist	optional output for actual distance from segment

Returns

0-based segment index for the closest segment (earliest segment in case of same distance)

Definition at line 1307 of file ptarray.c.

{
        const POINT2D *start = getPoint2d_cp(pa, 0), *end = NULL;
        uint32_t t, seg=0;
        double mindist=DBL_MAX;
 
        /* Loop through pointarray looking for nearest segment */
        for (t=1; t<pa->npoints; t++)
        {
                double dist_sqr;
                end = getPoint2d_cp(pa, t);
                dist_sqr = distance2d_sqr_pt_seg(qp, start, end);
 
                if (dist_sqr < mindist)
                {
                        mindist = dist_sqr;
                        seg=t-1;
                        if ( mindist == 0 )
                        {
                                LWDEBUG(3, "Breaking on mindist=0");
                                break;
                        }
                }
 
                start = end;
        }
 
        if ( dist ) *dist = sqrt(mindist);
        return seg;
}

References distance2d_sqr_pt_seg(), getPoint2d_cp(), LWDEBUG, and POINTARRAY::npoints.

Referenced by lwt_GetFaceContainingPoint(), and test_ptarray_closest_segment_2d().

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