/**
** @brief lwline_crossing_direction: returns the kind of #CG_LINE_CROSS_TYPE behavior of 2 linestrings
** @param l1 first line string
** @param l2 second line string
** @return a #CG_LINE_CROSS_TYPE
** LINE_NO_CROSS = 0
** LINE_CROSS_LEFT = -1
** LINE_CROSS_RIGHT = 1
** LINE_MULTICROSS_END_LEFT = -2
** LINE_MULTICROSS_END_RIGHT = 2
** LINE_MULTICROSS_END_SAME_FIRST_LEFT = -3
** LINE_MULTICROSS_END_SAME_FIRST_RIGHT = 3
**
*/
int lwline_crossing_direction(const LWLINE *l1, const LWLINE *l2)
{
int i = 0, j = 0, rv = 0;
POINT2D p1, p2, q1, q2;
POINTARRAY *pa1 = NULL, *pa2 = NULL;
int cross_left = 0;
int cross_right = 0;
int first_cross = 0;
int this_cross = 0;
pa1 = (POINTARRAY*)l1->points;
pa2 = (POINTARRAY*)l2->points;
/* One-point lines can't intersect (and shouldn't exist). */
if ( pa1->npoints < 2 || pa2->npoints < 2 )
return LINE_NO_CROSS;
LWDEBUGF(4, "l1 = %s", lwgeom_to_ewkt((LWGEOM*)l1));
LWDEBUGF(4, "l2 = %s", lwgeom_to_ewkt((LWGEOM*)l2));
/* Initialize first point of q */
rv = getPoint2d_p(pa2, 0, &q1);
for ( i = 1; i < pa2->npoints; i++ )
{
/* Update second point of q to next value */
rv = getPoint2d_p(pa2, i, &q2);
/* Initialize first point of p */
rv = getPoint2d_p(pa1, 0, &p1);
for ( j = 1; j < pa1->npoints; j++ )
{
/* Update second point of p to next value */
rv = getPoint2d_p(pa1, j, &p2);
this_cross = lw_segment_intersects(&p1, &p2, &q1, &q2);
LWDEBUGF(4, "i=%d, j=%d (%.8g %.8g, %.8g %.8g)", this_cross, i, j, p1.x, p1.y, p2.x, p2.y);
if ( this_cross == SEG_CROSS_LEFT )
{
LWDEBUG(4,"this_cross == SEG_CROSS_LEFT");
cross_left++;
if ( ! first_cross )
first_cross = SEG_CROSS_LEFT;
}
if ( this_cross == SEG_CROSS_RIGHT )
{
LWDEBUG(4,"this_cross == SEG_CROSS_RIGHT");
cross_right++;
if ( ! first_cross )
first_cross = SEG_CROSS_LEFT;
}
/*
** Crossing at a co-linearity can be turned handled by extending
** segment to next vertext and seeing if the end points straddle
** the co-linear segment.
*/
if ( this_cross == SEG_COLINEAR )
{
LWDEBUG(4,"this_cross == SEG_COLINEAR");
/* TODO: Add logic here and in segment_intersects()
continue;
*/
}
LWDEBUG(4,"this_cross == SEG_NO_INTERSECTION");
/* Turn second point of p into first point */
p1 = p2;
}
/* Turn second point of q into first point */
q1 = q2;
}
LWDEBUGF(4, "first_cross=%d, cross_left=%d, cross_right=%d", first_cross, cross_left, cross_right);
if ( !cross_left && !cross_right )
return LINE_NO_CROSS;
if ( !cross_left && cross_right == 1 )
return LINE_CROSS_RIGHT;
if ( !cross_right && cross_left == 1 )
return LINE_CROSS_LEFT;
if ( cross_left - cross_right == 1 )
return LINE_MULTICROSS_END_LEFT;
if ( cross_left - cross_right == -1 )
return LINE_MULTICROSS_END_RIGHT;
if ( cross_left - cross_right == 0 && first_cross == SEG_CROSS_LEFT )
return LINE_MULTICROSS_END_SAME_FIRST_LEFT;
if ( cross_left - cross_right == 0 && first_cross == SEG_CROSS_RIGHT )
return LINE_MULTICROSS_END_SAME_FIRST_RIGHT;
return LINE_NO_CROSS;
}
/*
** Test crossings side.
*/
static void test_lw_segment_intersects(void)
{
#define setpoint(p, x1, y1) {(p).x = (x1); (p).y = (y1);}
POINT2D p1, p2, q1, q2;
/* P: Vertical line at x=0 */
setpoint(p1, 0.0, 0.0);
p1.x = 0.0;
p1.y = 0.0;
p2.x = 0.0;
p2.y = 1.0;
/* Q: Horizontal line crossing left to right */
q1.x = -0.5;
q1.y = 0.5;
q2.x = 0.5;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_CROSS_RIGHT );
/* Q: Horizontal line crossing right to left */
q1.x = 0.5;
q1.y = 0.5;
q2.x = -0.5;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_CROSS_LEFT );
/* Q: Horizontal line not crossing right to left */
q1.x = 0.5;
q1.y = 1.5;
q2.x = -0.5;
q2.y = 1.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_NO_INTERSECTION );
/* Q: Horizontal line crossing at second vertex right to left */
q1.x = 0.5;
q1.y = 1.0;
q2.x = -0.5;
q2.y = 1.0;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_NO_INTERSECTION );
/* Q: Horizontal line crossing at first vertex right to left */
q1.x = 0.5;
q1.y = 0.0;
q2.x = -0.5;
q2.y = 0.0;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_CROSS_LEFT );
/* Q: Diagonal line with large range crossing at first vertex right to left */
q1.x = 0.5;
q1.y = 10.0;
q2.x = -0.5;
q2.y = -10.0;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_CROSS_LEFT );
/* Q: Diagonal line with large range crossing at second vertex right to left */
q1.x = 0.5;
q1.y = 11.0;
q2.x = -0.5;
q2.y = -9.0;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_NO_INTERSECTION );
/* Q: Horizontal touching from left at second vertex*/
q1.x = -0.5;
q1.y = 0.5;
q2.x = 0.0;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_NO_INTERSECTION );
/* Q: Horizontal touching from right at first vertex */
q1.x = 0.0;
q1.y = 0.5;
q2.x = 0.5;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_CROSS_RIGHT );
/* Q: Horizontal touching from left and far below on second vertex */
q1.x = -0.5;
q1.y = -10.5;
q2.x = 0.0;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_NO_INTERSECTION );
/* Q: Horizontal touching from right and far above on second vertex */
q1.x = 0.5;
q1.y = 10.5;
q2.x = 0.0;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_NO_INTERSECTION );
/* Q: Co-linear from top */
q1.x = 0.0;
q1.y = 10.0;
q2.x = 0.0;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_COLINEAR );
/* Q: Co-linear from bottom */
q1.x = 0.0;
q1.y = -10.0;
q2.x = 0.0;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_COLINEAR );
/* Q: Co-linear contained */
q1.x = 0.0;
q1.y = 0.4;
q2.x = 0.0;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_COLINEAR );
/* Q: Horizontal touching at end point from left */
q1.x = -0.5;
q1.y = 1.0;
q2.x = 0.0;
q2.y = 1.0;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_NO_INTERSECTION );
/* Q: Horizontal touching at end point from right */
q1.x = 0.0;
q1.y = 1.0;
q2.x = 0.0;
q2.y = 0.5;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_COLINEAR );
/* Q: Horizontal touching at start point from left */
q1.x = 0.0;
q1.y = 0.0;
q2.x = -0.5;
q2.y = 0.0;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_CROSS_LEFT );
/* Q: Horizontal touching at start point from right */
q1.x = 0.0;
q1.y = 0.0;
q2.x = 0.5;
q2.y = 0.0;
CU_ASSERT( lw_segment_intersects(&p1, &p2, &q1, &q2) == SEG_CROSS_RIGHT );
}
