segment_locate_along()

static int segment_locate_along ( const POINT4D *  p1, const POINT4D *  p2, double  m, double  offset, POINT4D *  pn  )

static

Definition at line 31 of file lwlinearreferencing.c.

References FP_MAX, FP_MIN, LW_FALSE, LW_TRUE, POINT4D::m, p4d_same(), POINT4D::x, POINT4D::y, and POINT4D::z.

Referenced by ptarray_locate_along(), and ptarray_locate_along_linear().

{
        double m1 = p1->m;
        double m2 = p2->m;
        double mprop;

        /* M is out of range, no new point generated. */
        if ( (m < FP_MIN(m1,m2)) || (m > FP_MAX(m1,m2)) )
        {
                return LW_FALSE;
        }

        if( m1 == m2 )
        {
                /* Degenerate case: same M on both points.
                   If they are the same point we just return one of them. */
                if ( p4d_same(p1,p2) )
                {
                        *pn = *p1;
                        return LW_TRUE;
                }
                /* If the points are different we split the difference */
                mprop = 0.5;
        }
        else
        {
                mprop = (m - m1) / (m2 - m1);
        }

        /* M is in range, new point to be generated. */
        pn->x = p1->x + (p2->x - p1->x) * mprop;
        pn->y = p1->y + (p2->y - p1->y) * mprop;
        pn->z = p1->z + (p2->z - p1->z) * mprop;
        pn->m = m;

        /* Offset to the left or right, if necessary. */
        if ( offset != 0.0 )
        {
                double theta = atan2(p2->y - p1->y, p2->x - p1->x);
                pn->x -= sin(theta) * offset;
                pn->y += cos(theta) * offset;
        }

        return LW_TRUE;
}

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