lw_dist3d_pt_seg()

int lw_dist3d_pt_seg	(	POINT3DZ *	p,
		POINT3DZ *	A,
		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 767 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 vertexes,
        compared to mindistance which can be between
        two vertexes 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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