/// <summary>
/// Determines what a person sees given person's position and direction of a view
/// </summary>
/// <param name="position">coordinates of a viewer</param>
/// <param name="bearing">direction at which viewer looks (bearing) in radians</param>
/// <returns>list of objects' descriptions</returns>
public IEnumerable <string> At(GeoPoint position, double bearing)
{
if (position == null)
{
throw new ArgumentNullException("position");
}
var boundingBox = GeoCalc.GetBoundingBox(position, Adjustment.BoundingBoxHeight, Adjustment.BoundingBoxWidth);
var mapData = ApiClient.GetDataInBoundingBox(ApiUrl, boundingBox);
var objectsOfImportance = OsmApiDataProcessor.GetObjectsOfImportance(mapData);
return(FilterObjectsByPositionAndBearing(objectsOfImportance, position, bearing));
}
/// <summary>
/// Filters out only objects in a person's direction of a view
/// </summary>
private IEnumerable <string> FilterObjectsByPositionAndBearing(OsmObjectsOfImportance objects, GeoPoint position, double bearing)
{
Debug.Assert(objects != null, "objects == null");
Debug.Assert(position != null, "position == null");
var testingPoints = GetPointsAlongBearing(position, bearing);
// filter objects
var filterSingleNodesTask = Task.Factory.StartNew(() => FilterSingleNodes(objects.SingleNodes, testingPoints));
var filterBuildingsWaysTask = Task.Factory.StartNew(() =>
{
// filter buildings' ways by testing if some point along a person's direction of view is inside the way
foreach (var point in testingPoints)
{
foreach (var way in objects.BuildingsWays)
{
if (GeoCalc.IsPointInsidePolygon(point, way.Nodes))
{
return new { TestingPoint = point, Way = way }
}
;
}
}
return(null);
});
Task.WaitAll(filterSingleNodesTask, filterBuildingsWaysTask);
// print out objects' descriptions
var building = filterBuildingsWaysTask.Result;
if (building != null)
{
yield return(BuildingWayDescription(building.Way));
}
foreach (var node in filterSingleNodesTask.Result)
{
if (building == null ||
GeoCalc.GetDistance(node, building.TestingPoint) < Adjustment.MaxDeviationFromBearingBuildingIntersection)
{
yield return(SingleNodeDescription(node));
}
}
}
/// <summary>
/// Filters single nodes by testing whether they are close to the points along a person's direction of view
/// </summary>
private ICollection <OsmNode> FilterSingleNodes(ICollection <OsmNode> singleNodes, IEnumerable <GeoPoint> testingPoints)
{
Debug.Assert(singleNodes != null, "singleNodes == null");
Debug.Assert(testingPoints != null, "testingPoints == null");
var result = new List <OsmNode>();
foreach (var point in testingPoints)
{
foreach (var node in singleNodes)
{
if (!result.Contains(node) && GeoCalc.GetDistance(point, node) < Adjustment.MaxDeviationFromBearing)
{
result.Add(node);
}
}
}
return(result);
}
/// <summary>
/// Returns a collection of physical locations along a person's direction of a view ordered by distance (ascending)
/// </summary>
private IEnumerable <GeoPoint> GetPointsAlongBearing(GeoPoint position, double bearing)
{
Debug.Assert(position != null, "position == null");
var pointsCount =
(int)
Math.Sqrt(Adjustment.BoundingBoxHeight * Adjustment.BoundingBoxHeight +
Adjustment.BoundingBoxWidth * Adjustment.BoundingBoxWidth) / 2 * Adjustment.TestByBearingStepLength;
var points = new GeoPoint[pointsCount];
for (var i = 0; i < pointsCount; i++)
{
var destination = GeoCalc.GetDestination(position, bearing, Adjustment.TestByBearingStepLength * i + 1);
points[i] = new GeoPoint(destination.Latitude, destination.Longitude);
}
return(points);
}
