internal static double DistanceToIntersection(gVertex centre, gVertex maxVertex, gEdge e)
{
var centreProj = gVertex.ByCoordinates(centre.X, centre.Y, 0);
var maxProj = gVertex.ByCoordinates(maxVertex.X, maxVertex.Y, 0);
var startProj = gVertex.ByCoordinates(e.StartVertex.X, e.StartVertex.Y, 0);
var endProj = gVertex.ByCoordinates(e.EndVertex.X, e.EndVertex.Y, 0);
gEdge rayEdge = gEdge.ByStartVertexEndVertex(centreProj, maxProj);
gEdge edgeProj = gEdge.ByStartVertexEndVertex(startProj, endProj);
gBase intersection = rayEdge.Intersection(edgeProj);
if (intersection != null && intersection.GetType() == typeof(gVertex))
{
return(centre.DistanceTo((gVertex)intersection));
}
else
{
return(0);
}
}
/// <summary>
///
/// </summary>
/// <param name="centre"></param>
/// <param name="baseGraph"></param>
/// <param name="origin"></param>
/// <param name="destination"></param>
/// <param name="singleVertices"></param>
/// <param name="scan"></param>
/// <returns name="visibleVertices">List of vertices visible from the analysed vertex</returns>
public static List <gVertex> VisibleVertices(
gVertex centre,
Graph baseGraph,
gVertex origin = null,
gVertex destination = null,
List <gVertex> singleVertices = null,
bool halfScan = true,
bool reducedGraph = true,
bool maxVisibility = false)
{
#region Initialize variables and sort vertices
List <gEdge> edges = baseGraph.edges;
List <gVertex> vertices = baseGraph.vertices;
if (origin != null)
{
vertices.Add(origin);
}
if (destination != null)
{
vertices.Add(destination);
}
if (singleVertices != null)
{
vertices.AddRange(singleVertices);
}
gVertex maxVertex = vertices.OrderByDescending(v => v.DistanceTo(centre)).First();
double maxDistance = centre.DistanceTo(maxVertex) * 1.5;
//vertices = vertices.OrderBy(v => Point.RadAngle(centre.point, v.point)).ThenBy(v => centre.DistanceTo(v)).ToList();
vertices = gVertex.OrderByRadianAndDistance(vertices, centre);
#endregion
#region Initialize openEdges
//Initialize openEdges with any intersection edges on the half line
//from centre to maxDistance on the XAxis
List <EdgeKey> openEdges = new List <EdgeKey>();
double xMax = Math.Abs(centre.X) + 1.5 * maxDistance;
gEdge halfEdge = gEdge.ByStartVertexEndVertex(centre, gVertex.ByCoordinates(xMax, centre.Y, centre.Z));
foreach (gEdge e in edges)
{
if (e.Contains(centre))
{
continue;
}
if (halfEdge.Intersects(e))
{
if (e.StartVertex.OnEdge(halfEdge))
{
continue;
}
if (e.EndVertex.OnEdge(halfEdge))
{
continue;
}
EdgeKey k = new EdgeKey(halfEdge, e);
Core.List.AddItemSorted(openEdges, k);
}
}
#endregion
List <gVertex> visibleVertices = new List <gVertex>();
gVertex prev = null;
bool prevVisible = false;
for (var i = 0; i < vertices.Count; i++)
{
gVertex vertex = vertices[i];
if (vertex.Equals(centre) || vertex.Equals(prev))
{
continue;
} // v == to centre or to previous when updating graph
//Check only half of vertices as eventually they will become 'v'
if (halfScan && gVertex.RadAngle(centre, vertex) > Math.PI)
{
break;
}
//Removing clock wise edges incident on v
if (openEdges.Count > 0 && baseGraph.graph.ContainsKey(vertex))
{
foreach (gEdge edge in baseGraph.graph[vertex])
{
int orientation = gVertex.Orientation(centre, vertex, edge.GetVertexPair(vertex));
if (orientation == -1)
{
EdgeKey k = new EdgeKey(centre, vertex, edge);
int index = Core.List.Bisect(openEdges, k) - 1;
index = (index < 0) ? openEdges.Count - 1 : index;
if (openEdges.Count > 0 && openEdges.ElementAt(index).Equals(k))
{
openEdges.RemoveAt(index);
}
}
}
}
//Checking if p is visible from p.
bool isVisible = false;
//No collinear vertices
if (prev == null || gVertex.Orientation(centre, prev, vertex) != 0 || !prev.OnEdge(centre, vertex))
{
if (openEdges.Count == 0)
{
isVisible = true;
}
else if (!EdgeIntersect(centre, vertex, openEdges[0].Edge))
{
isVisible = true;
}
}
//For collinear vertices, if previous was not visible, vertex is not either
else if (!prevVisible)
{
isVisible = false;
}
//For collinear vertices, if prev was visible need to check that
//the edge from prev to vertex does not intersect with any open edge
else
{
isVisible = true;
foreach (EdgeKey k in openEdges)
{
//if (!k.edge.Contains(prev) && EdgeIntersect(prev, vertex, k.edge))
if (EdgeIntersect(prev, vertex, k.Edge) && !k.Edge.Contains(prev))
{
isVisible = false;
break;
}
}
// If visible (doesn't intersect any open edge) and edge 'prev-vertex'
// is in any polygon, vertex is visible if it belongs to a external boundary
if (isVisible && EdgeInPolygon(prev, vertex, baseGraph, maxDistance))
{
isVisible = IsBoundaryVertex(vertex, baseGraph);
}
// If still visible (not inside polygon or is boundary vertex),
// if not on 'centre-prev' edge means there is a gap between prev and vertex
if (isVisible && !vertex.OnEdge(centre, prev))
{
isVisible = !IsBoundaryVertex(vertex, baseGraph);
}
}
//If vertex is visible and centre belongs to any polygon, checks
//if the visible edge is interior to its polygon
if (isVisible && centre.polygonId >= 0 && !baseGraph.GetAdjecentVertices(centre).Contains(vertex))
{
if (IsBoundaryVertex(centre, baseGraph) && IsBoundaryVertex(vertex, baseGraph))
{
isVisible = EdgeInPolygon(centre, vertex, baseGraph, maxDistance);
}
else
{
isVisible = !EdgeInPolygon(centre, vertex, baseGraph, maxDistance);
}
}
prev = vertex;
prevVisible = isVisible;
if (isVisible)
{
// Check reducedGraph if vertices belongs to different polygons
if (reducedGraph && centre.polygonId != vertex.polygonId)
{
bool isOriginExtreme = true;
bool isTargetExtreme = true;
// For reduced graphs, it is checked if the edge is extrem or not.
// For an edge to be extreme, the edges coincident at the start and end vertex
// will have the same orientation (both clock or counter-clock wise)
// Vertex belongs to a polygon
if (centre.polygonId >= 0 && !IsBoundaryVertex(centre, baseGraph))
{
var orientationsOrigin = baseGraph.GetAdjecentVertices(centre).Select(otherVertex => gVertex.Orientation(vertex, centre, otherVertex)).ToList();
isOriginExtreme = orientationsOrigin.All(o => o == orientationsOrigin.First());
}
if (vertex.polygonId >= 0 && !IsBoundaryVertex(vertex, baseGraph))
{
var orientationsTarget = baseGraph.GetAdjecentVertices(vertex).Select(otherVertex => gVertex.Orientation(centre, vertex, otherVertex)).ToList();
isTargetExtreme = orientationsTarget.All(o => o == orientationsTarget.First());
}
if (isTargetExtreme || isOriginExtreme)
{
visibleVertices.Add(vertex);
}
}
else
{
visibleVertices.Add(vertex);
}
}
if (baseGraph.Contains(vertex))
{
foreach (gEdge e in baseGraph.graph[vertex])
{
if (!e.Contains(centre) && gVertex.Orientation(centre, vertex, e.GetVertexPair(vertex)) == 1)
{
EdgeKey k = new EdgeKey(centre, vertex, e);
Core.List.AddItemSorted(openEdges, k);
}
}
}
if (isVisible && maxVisibility && vertex.polygonId >= 0)
{
List <gVertex> vertexPairs = baseGraph.GetAdjecentVertices(vertex);
int firstOrientation = gVertex.Orientation(centre, vertex, vertexPairs[0]);
int secondOrientation = gVertex.Orientation(centre, vertex, vertexPairs[1]);
//if both edges lie on the same side of the centre-vertex edge or one of them is colinear
if (firstOrientation == secondOrientation || firstOrientation == 0 || secondOrientation == 0)
{
gVertex rayVertex = vertex.Translate(gVector.ByTwoVertices(centre, vertex), maxDistance);
gEdge rayEdge = gEdge.ByStartVertexEndVertex(centre, rayVertex);
gVertex projectionVertex = null;
foreach (EdgeKey ek in openEdges)
{
gBase intersection = rayEdge.Intersection(ek.Edge);
if (intersection != null && intersection is gVertex && !(intersection as gVertex).Equals(vertex))
{
projectionVertex = intersection as gVertex;
break;
}
}
if (projectionVertex != null)
{
// if edges are before rayEdge, projection Vertex goes after vertex
if (firstOrientation == -1 || secondOrientation == -1)
{
visibleVertices.Add(projectionVertex);
}
else
{
visibleVertices.Insert(visibleVertices.Count - 1, projectionVertex);
}
}
}
}
}
return(visibleVertices);
}