RTreeFindLineSegments()

LWMLINE * RTreeFindLineSegments	(	RTREE_NODE *	root,
		double	value
	)

Retrieves a collection of line segments given the root and crossing value.

The collection is a multilinestring consisting of two point lines representing the segments of the ring that may be crossed by the horizontal projection line at the given y value.

Definition at line 450 of file lwgeom_rtree.c.

{
        LWMLINE *tmp, *result;
        LWGEOM **lwgeoms;
 
        POSTGIS_DEBUGF(2, "RTreeFindLineSegments called for tree %p and value %8.3f", root, value);
 
        result = NULL;
 
        if (!IntervalIsContained(root->interval, value))
        {
                POSTGIS_DEBUGF(3, "RTreeFindLineSegments %p: not contained.", root);
 
                return NULL;
        }
 
        /* If there is a segment defined for this node, include it. */
        if (root->segment)
        {
                POSTGIS_DEBUGF(3, "RTreeFindLineSegments %p: adding segment %p %d.", root, root->segment, root->segment->type);
 
                lwgeoms = lwalloc(sizeof(LWGEOM *));
                lwgeoms[0] = (LWGEOM *)root->segment;
 
                POSTGIS_DEBUGF(3, "Found geom %p, type %d, dim %d", root->segment, root->segment->type, lwgeom_ndims((LWGEOM *)(root->segment)));
 
                result = (LWMLINE *)lwcollection_construct(MULTILINETYPE, SRID_UNKNOWN, NULL, 1, lwgeoms);
        }
 
        /* If there is a left child node, recursively include its results. */
        if (root->leftNode)
        {
                POSTGIS_DEBUGF(3, "RTreeFindLineSegments %p: recursing left.", root);
 
                tmp = RTreeFindLineSegments(root->leftNode, value);
                if (tmp)
                {
                        POSTGIS_DEBUGF(3, "Found geom %p, type %d, dim %d", tmp, tmp->type, lwgeom_ndims((LWGEOM *)tmp));
 
                        if (result)
                                result = RTreeMergeMultiLines(result, tmp);
                        else
                                result = tmp;
                }
        }
 
        /* Same for any right child. */
        if (root->rightNode)
        {
                POSTGIS_DEBUGF(3, "RTreeFindLineSegments %p: recursing right.", root);
 
                tmp = RTreeFindLineSegments(root->rightNode, value);
                if (tmp)
                {
                        POSTGIS_DEBUGF(3, "Found geom %p, type %d, dim %d", tmp, tmp->type, lwgeom_ndims((LWGEOM *)tmp));
 
                        if (result)
                                result = RTreeMergeMultiLines(result, tmp);
                        else
                                result = tmp;
                }
        }
 
        return result;
}

References rtree_node::interval, IntervalIsContained(), rtree_node::leftNode, lwalloc(), lwcollection_construct(), lwgeom_ndims(), MULTILINETYPE, rtree_node::rightNode, RTreeFindLineSegments(), RTreeMergeMultiLines(), rtree_node::segment, SRID_UNKNOWN, LWLINE::type, and LWMLINE::type.

Referenced by point_in_ring_rtree(), and RTreeFindLineSegments().

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