lw_dist2d_pt_seg()

int lw_dist2d_pt_seg	(	const POINT2D *	p,
		const POINT2D *	A,
		const POINT2D *	B,
		DISTPTS *	dl
	)

lw_dist2d_comp from p to line A->B This one is now sending every occation to lw_dist2d_pt_pt Before it was handling occations where r was between 0 and 1 internally and just returning the distance without identifying the points.

To get this points it was nessecary to change and it also showed to be about 10faster.

Definition at line 2205 of file measures.c.

References DIST_MAX, DIST_MIN, DISTPTS::distance, lw_dist2d_pt_pt(), DISTPTS::mode, DISTPTS::p1, DISTPTS::p2, r, POINT2D::x, and POINT2D::y.

Referenced by lw_dist2d_pt_arc(), lw_dist2d_pt_ptarray(), lw_dist2d_seg_arc(), lw_dist2d_seg_seg(), and lw_dist2d_selected_seg_seg().

{
        POINT2D c;
        double  r;
        /*if start==end, then use pt distance */
        if (  ( A->x == B->x) && (A->y == B->y) )
        {
                return lw_dist2d_pt_pt(p,A,dl);
        }
        /*
         * otherwise, we use comp.graphics.algorithms
         * Frequently Asked Questions method
         *
         *  (1)        AC dot AB
         *         r = ---------
         *              ||AB||^2
         *      r has the following meaning:
         *      r=0 P = A
         *      r=1 P = B
         *      r<0 P is on the backward extension of AB
         *      r>1 P is on the forward extension of AB
         *      0<r<1 P is interior to AB
         */

        r = ( (p->x-A->x) * (B->x-A->x) + (p->y-A->y) * (B->y-A->y) )/( (B->x-A->x)*(B->x-A->x) +(B->y-A->y)*(B->y-A->y) );

        /*This is for finding the maxdistance.
        the maxdistance have to be between two vertexes,
        compared to mindistance which can be between
        tvo vertexes vertex.*/
        if (dl->mode == DIST_MAX)
        {
                if (r>=0.5)
                {
                        return lw_dist2d_pt_pt(p,A,dl);
                }
                if (r<0.5)
                {
                        return lw_dist2d_pt_pt(p,B,dl);
                }
        }

        if (r<0)        /*If p projected on the line is outside point A*/
        {
                return lw_dist2d_pt_pt(p,A,dl);
        }
        if (r>=1)       /*If p projected on the line is outside point B or on point B*/
        {
                return lw_dist2d_pt_pt(p,B,dl);
        }

        /*If the point p is on the segment this is a more robust way to find out that*/
        if (( ((A->y-p->y)*(B->x-A->x)==(A->x-p->x)*(B->y-A->y) ) ) && (dl->mode ==  DIST_MIN))
        {
                dl->distance = 0.0;
                dl->p1 = *p;
                dl->p2 = *p;
        }

        /*If the projection of point p on the segment is between A and B
        then we find that "point on segment" and send it to lw_dist2d_pt_pt*/
        c.x=A->x + r * (B->x-A->x);
        c.y=A->y + r * (B->y-A->y);

        return lw_dist2d_pt_pt(p,&c,dl);
}

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