/// <summary>
/// Whether the winding order of a given loop is clockwise, with normalization
/// for loops crossing the antimeridian.
/// </summary>
/// <param name="loop">The loop to check</param>
/// <param name="isTransmeridian">Whether the loop crosses the antimeridian</param>
/// <returns>Whether the loop is clockwise</returns>
/// <!-- Based off 3.1.1 -->
public static bool isClockwiseNormalizedGeofence(Geofence loop, bool isTransmeridian)
{
double sum = 0;
GeoCoord a;
GeoCoord b;
int loopIndex = -1;
while (true)
{
if (++loopIndex >= loop.numVerts)
{
break;
}
a = new GeoCoord(loop.verts[loopIndex].lat, loop.verts[loopIndex].lon);
b = new GeoCoord
(
loop.verts[(loopIndex + 1) % loop.numVerts].lat,
loop.verts[(loopIndex + 1) % loop.numVerts].lon
);
// If we identify a transmeridian arc (> 180 degrees longitude),
// start over with the transmeridian flag set
if (!isTransmeridian && Math.Abs(a.lon - b.lon) > Constants.M_PI)
{
return(isClockwiseNormalizedGeofence(loop, true));
}
sum += (NORMALIZE_LON(b.lon, isTransmeridian) -
NORMALIZE_LON(a.lon, isTransmeridian)) *
(b.lat + a.lat);
}
return(sum > 0);
}
/// <summary>
/// Create a bounding box from a simple polygon loop.
/// Known limitations:
/// - Does not support polygons with two adjacent points > 180 degrees of
/// longitude apart. These will be interpreted as crossing the antimeridian.
/// - Does not currently support polygons containing a pole.
/// </summary>
/// <param name="loop">Loop of coordinates</param>
/// <param name="bbox">Output bbox</param>
/// <!-- Based off 3.1.1 -->
public static void bboxFromGeofence(ref Geofence loop, ref BBox bbox)
{
// Early exit if there are no vertices
if (loop.numVerts == 0)
{
bbox = new BBox();
return;
}
bbox.south = Double.MaxValue;
bbox.west = Double.MaxValue;
bbox.north = -Double.MaxValue;
bbox.east = -Double.MaxValue;
double minPosLon = Double.MaxValue;
double maxNegLon = -Double.MaxValue;
bool isTransmeridian = false;
double lat;
double lon;
GeoCoord coord;
GeoCoord next;
int loopIndex = -1;
while (true)
{
if (++loopIndex >= loop.numVerts)
{
break;
}
coord = new GeoCoord(loop.verts[loopIndex].lat, loop.verts[loopIndex].lon);
next = new GeoCoord
(
loop.verts[(loopIndex + 1) % loop.numVerts].lat,
loop.verts[(loopIndex + 1) % loop.numVerts].lon
);
lat = coord.lat;
lon = coord.lon;
if (lat < bbox.south)
{
bbox.south = lat;
}
if (lon < bbox.west)
{
bbox.west = lon;
}
if (lat > bbox.north)
{
bbox.north = lat;
}
if (lon > bbox.east)
{
bbox.east = lon;
}
// Save the min positive and max negative longitude for
// use in the transmeridian case
if (lon > 0 && lon < minPosLon)
{
minPosLon = lon;
}
if (lon < 0 && lon > maxNegLon)
{
maxNegLon = lon;
}
// check for arcs > 180 degrees longitude, flagging as transmeridian
if (Math.Abs(lon - next.lon) > Constants.M_PI)
{
isTransmeridian = true;
}
}
// Swap east and west if transmeridian
if (isTransmeridian)
{
bbox.east = maxNegLon;
bbox.west = minPosLon;
}
}
/// <summary>
/// Whether the winding order of a given loop is clockwise. In GeoJSON,
/// clockwise loops are always inner loops (holes).
/// </summary>
/// <param name="loop">The loop to check</param>
/// <returns>Whether the loop is clockwise</returns>
/// <!-- Based off 3.1.1 -->
public static bool isClockwiseGeofence(Geofence loop)
{
return(isClockwiseNormalizedGeofence(loop, false));
}
/// <summary>
/// pointInside is the core loop of the point-in-poly algorithm
/// </summary>
/// <param name="loop">The loop to check</param>
/// <param name="bbox">The bbox for the loop being tested</param>
/// <param name="coord">The coordinate to check</param>
/// <returns>Whether the point is contained</returns>
/// <!-- Based off 3.1.1 -->
public static bool pointInsideGeofence(ref Geofence loop, ref BBox bbox, ref GeoCoord coord)
{
// fail fast if we're outside the bounding box
if (!BBox.bboxContains(bbox, coord))
{
return(false);
}
bool isTransmeridian = BBox.bboxIsTransmeridian(bbox);
bool contains = false;
double lat = coord.lat;
double lng = NORMALIZE_LON(coord.lon, isTransmeridian);
GeoCoord a;
GeoCoord b;
int loopIndex = -1;
while (true)
{
if (++loopIndex >= loop.numVerts)
{
break;
}
a = new GeoCoord(loop.verts[loopIndex].lat, loop.verts[loopIndex].lon);
b = new GeoCoord
(
loop.verts[(loopIndex + 1) % loop.numVerts].lat,
loop.verts[(loopIndex + 1) % loop.numVerts].lon
);
//b = loop.verts[(loopIndex + 1) % loop.numVerts];
// Ray casting algo requires the second point to always be higher
// than the first, so swap if needed
if (a.lat > b.lat)
{
GeoCoord tmp = a;
a = b;
b = tmp;
}
// If we're totally above or below the latitude ranges, the test
// ray cannot intersect the line segment, so let's move on
if (lat < a.lat || lat > b.lat)
{
continue;
}
double aLng = NORMALIZE_LON(a.lon, isTransmeridian);
double bLng = NORMALIZE_LON(b.lon, isTransmeridian);
// Rays are cast in the longitudinal direction, in case a point
// exactly matches, to decide tiebreakers, bias westerly
if (Math.Abs(aLng - lng) < Constants.DBL_EPSILON || Math.Abs(bLng - lng) < Constants.DBL_EPSILON)
{
lng -= Constants.DBL_EPSILON;
}
// For the latitude of the point, compute the longitude of the
// point that lies on the line segment defined by a and b
// This is done by computing the percent above a the lat is,
// and traversing the same percent in the longitudinal direction
// of a to b
double ratio = (lat - a.lat) / (b.lat - a.lat);
double testLng =
NORMALIZE_LON(aLng + (bLng - aLng) * ratio, isTransmeridian);
// Intersection of the ray
if (testLng > lng)
{
contains = !contains;
}
}
return(contains);
}
/// <summary>
/// Create a bounding box from a Geofence
/// </summary>
/// <param name="Geofence">Input <see cref="Geofence"/></param>
/// <param name="bbox">Output bbox</param>
/// <!-- Based off 3.1.1 -->
public static void bboxFromGeofence(Geofence Geofence, ref BBox bbox)
{
bboxFromVertices(Geofence.verts.ToList(), Geofence.numVerts, ref bbox);
}