lw_dist3d_pt_seg()

int lw_dist3d_pt_seg	(	const POINT3DZ *	p,
		const POINT3DZ *	A,
		const POINT3DZ *	B,
		DISTPTS3D *	dl
	)

If searching for min distance, this one finds the closest point on segment A-B from p.

if searching for max distance it just sends p-A and p-B to pt-pt calculation

Definition at line 1026 of file measures3d.c.

{
        POINT3DZ c;
        double r;
        /*if start==end, then use pt distance */
        if ((A->x == B->x) && (A->y == B->y) && (A->z == B->z))
        {
                return lw_dist3d_pt_pt(p, A, dl);
        }
 
        r = ((p->x - A->x) * (B->x - A->x) + (p->y - A->y) * (B->y - A->y) + (p->z - A->z) * (B->z - A->z)) /
            ((B->x - A->x) * (B->x - A->x) + (B->y - A->y) * (B->y - A->y) + (B->z - A->z) * (B->z - A->z));
 
        /*This is for finding the 3Dmaxdistance.
        the maxdistance have to be between two vertices,
        compared to mindistance which can be between
        two vertices vertex.*/
        if (dl->mode == DIST_MAX)
        {
                if (r >= 0.5)
                        return lw_dist3d_pt_pt(p, A, dl);
                if (r < 0.5)
                        return lw_dist3d_pt_pt(p, B, dl);
        }
 
        if (r <= 0) /*If the first vertex A is closest to the point p*/
                return lw_dist3d_pt_pt(p, A, dl);
        if (r >= 1) /*If the second vertex B is closest to the point p*/
                return lw_dist3d_pt_pt(p, B, dl);
 
        /*else if the point p is closer to some point between a and b
        then we find that point and send it to lw_dist3d_pt_pt*/
        c.x = A->x + r * (B->x - A->x);
        c.y = A->y + r * (B->y - A->y);
        c.z = A->z + r * (B->z - A->z);
 
        return lw_dist3d_pt_pt(p, &c, dl);
}

References DIST_MAX, lw_dist3d_pt_pt(), DISTPTS3D::mode, r, POINT3DZ::x, POINT3DZ::y, and POINT3DZ::z.

Referenced by lw_dist3d_pt_ptarray(), and lw_dist3d_seg_seg().

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