/// <summary>
/// Returns the radius of a given hexagon in kilometers
/// </summary>
/// <param name="h3Index">Index of the hexagon</param>
/// <returns>radius of hexagon in kilometers</returns>
/// <!-- Based off 3.1.1 -->
static double _hexRadiusKm(H3Index h3Index)
{
// There is probably a cheaper way to determine the radius of a
// hexagon, but this way is conceptually simple
GeoCoord h3Center = new GeoCoord();
GeoBoundary h3Boundary = new GeoBoundary();
H3Index.h3ToGeo(h3Index, ref h3Center);
H3Index.h3ToGeoBoundary(h3Index, ref h3Boundary);
return(GeoCoord._geoDistKm(h3Center, h3Boundary.verts));
}
/// <summary>
/// Internal: Create a vertex graph from a set of hexagons. It is the
/// responsibility of the caller to call destroyVertexGraph on the populated
/// graph, otherwise the memory in the graph nodes will not be freed.
/// </summary>
///
/// <param name="h3Set">Set of hexagons</param>
/// <param name="numHexes">Number of hexagons in the set</param>
/// <param name="graph">Output graph</param>
/// <!-- Based off 3.1.1 -->
public static void h3SetToVertexGraph(ref List <H3Index> h3Set, int numHexes,
ref VertexGraph graph)
{
GeoBoundary vertices = new GeoBoundary();
GeoCoord fromVertex = new GeoCoord();
GeoCoord toVertex = new GeoCoord();
VertexGraph.VertexNode edge;
if (numHexes < 1)
{
// We still need to init the graph, or calls to destroyVertexGraph will
// fail
graph = new VertexGraph(0, 0);
return;
}
int res = H3Index.H3_GET_RESOLUTION(h3Set[0]);
const int minBuckets = 6;
// TODO: Better way to calculate/guess?
int numBuckets = numHexes > minBuckets ? numHexes : minBuckets;
graph = new VertexGraph(numBuckets, res);
// Iterate through every hexagon
for (int i = 0; i < numHexes; i++)
{
H3Index.h3ToGeoBoundary(h3Set[i], ref vertices);
// iterate through every edge
for (int j = 0; j < vertices.numVerts; j++)
{
fromVertex = new GeoCoord(vertices.verts[j].lat, vertices.verts[j].lon);
//fromVtx = vertices.verts[j];
int idx = (j + 1) % vertices.numVerts;
toVertex = new GeoCoord(vertices.verts[idx].lat, vertices.verts[idx].lon);
//toVtx = vertices.verts[(j + 1) % vertices.numVerts];
// If we've seen this edge already, it will be reversed
edge = VertexGraph.findNodeForEdge(ref graph, toVertex, fromVertex);
if (edge != null)
{
// If we've seen it, drop it. No edge is shared by more than 2
// hexagons, so we'll never see it again.
VertexGraph.removeVertexNode(ref graph, ref edge);
}
else
{
// Add a new node for this edge
VertexGraph.addVertexNode(ref graph, fromVertex, toVertex);
}
}
}
}
/// <summary>
/// Provides the coordinates defining the unidirectional edge.
/// </summary>
/// <param name="edge">The unidirectional edge H3Index</param>
/// <param name="gb">
/// The geoboundary object to store the edge coordinates.
/// </param>
/// <!-- Based off 3.1.1 -->
public static void getH3UnidirectionalEdgeBoundary(H3Index edge, ref GeoBoundary gb)
{
// TODO: More efficient solution :)
GeoBoundary origin = new GeoBoundary();
GeoBoundary destination = new GeoBoundary();
GeoCoord postponedVertex = new GeoCoord();
bool hasPostponedVertex = false;
H3Index.h3ToGeoBoundary(getOriginH3IndexFromUnidirectionalEdge(edge), ref origin);
H3Index.h3ToGeoBoundary(getDestinationH3IndexFromUnidirectionalEdge(edge), ref destination);
int k = 0;
for (int i = 0; i < origin.numVerts; i++)
{
if (_hasMatchingVertex(origin.verts[i], destination))
{
// If we are on vertex 0, we need to handle the case where it's the
// end of the edge, not the beginning.
if (i == 0 &&
!_hasMatchingVertex(origin.verts[i + 1], destination))
{
postponedVertex = origin.verts[i];
hasPostponedVertex = true;
}
else
{
gb.verts[k] = origin.verts[i];
k++;
}
}
}
// If we postponed adding the last vertex, add it now
if (hasPostponedVertex)
{
gb.verts[k] = postponedVertex;
k++;
}
gb.numVerts = k;
}
