azimuth_pt_pt()

int azimuth_pt_pt	(	const POINT2D *	A,
		const POINT2D *	B,
		double *	d
	)

Compute the azimuth of segment AB in radians.

Return 0 on exception (same point), 1 otherwise.

Definition at line 2427 of file measures.c.

References POINT2D::x, and POINT2D::y.

Referenced by _lwt_AddEdge(), _lwt_FindAdjacentEdges(), _lwt_InitEdgeEndByLine(), and LWGEOM_azimuth().

{
        if ( A->x == B->x )
        {
                if ( A->y < B->y ) *d=0.0;
                else if ( A->y > B->y ) *d=M_PI;
                else return 0;
                return 1;
        }

        if ( A->y == B->y )
        {
                if ( A->x < B->x ) *d=M_PI/2;
                else if ( A->x > B->x ) *d=M_PI+(M_PI/2);
                else return 0;
                return 1;
        }

        if ( A->x < B->x )
        {
                if ( A->y < B->y )
                {
                        *d=atan(fabs(A->x - B->x) / fabs(A->y - B->y) );
                }
                else /* ( A->y > B->y )  - equality case handled above */
                {
                        *d=atan(fabs(A->y - B->y) / fabs(A->x - B->x) )
                           + (M_PI/2);
                }
        }

        else /* ( A->x > B->x ) - equality case handled above */
        {
                if ( A->y > B->y )
                {
                        *d=atan(fabs(A->x - B->x) / fabs(A->y - B->y) )
                           + M_PI;
                }
                else /* ( A->y < B->y )  - equality case handled above */
                {
                        *d=atan(fabs(A->y - B->y) / fabs(A->x - B->x) )
                           + (M_PI+(M_PI/2));
                }
        }

        return 1;
}

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