/// <summary>
/// Creates a random convex polygon.
/// </summary>
/// <param name="generationSize"></param>
/// <param name="maxOffset"></param>
/// <returns></returns>
public static List<Vertex> RandomConvexPolygon(int generationSize, int maxOffset)
{
int offsetSmaller = 4;
RandomGenerator = new Random();
var gm = new GraphManager();
var edges = new List<Edge>();
//Create two random vertices
var v1 = RandomVertex(maxOffset / 2, maxOffset / 2 + maxOffset / offsetSmaller, maxOffset / 2, maxOffset / 2 + maxOffset / offsetSmaller);
var v2 = RandomVertex(maxOffset / 2 - maxOffset / offsetSmaller, maxOffset / 2, maxOffset / 2 - maxOffset / offsetSmaller, maxOffset / 2);
gm.AddVertex(v1);
gm.AddVertex(v2);
edges.Add(gm.CreateEdge(v1, v2));
edges.Add(gm.CreateEdge(v2, v1));
//Create all new vertices and edges by splitting an edge in two and introducing a new vertex.
int i = 2;
while(i < generationSize) {
double vertexLength = 0;
int index = 0;
//Ignore everythin for a smaller offset than 30. Basically a filter to not create points too close to each other
while (vertexLength < 30)
{
index = RandomGenerator.Next(0, edges.Count - 1);
vertexLength = edges[index].CreateLine().GetLength();
}
var oldEdge = edges[index];
var count = edges.Count;
edges.RemoveAt(index); //Remove old edge
edges.AddRange(SplitConvexEdge(gm, oldEdge, maxOffset/20, (i+1)%count)); //And add new ones
i++;
}
gm.RemoveAllEdges(); //Clean up the graph by removing all edges from the vertices
return gm.Vertices;
}
public Chews()
{
RandomGenerator = new Random();
GM = new GraphManager();
}
/// <summary>
/// Splits an edge on a convex polygon into two edges by adding a vertex on a random position
/// While keeping the Convex constraint.
/// </summary>
/// <param name="gm"></param>
/// <param name="e"></param>
/// <param name="maxOffset"></param>
/// <param name="index"></param>
/// <returns></returns>
public static List<Edge> SplitConvexEdge(GraphManager gm, Edge e, int maxOffset, int index)
{
var edgeLine = e.CreateLine();
List<Edge> result = new List<Edge>();
//Create random point on the edge
var offset = Convert.ToDouble(RandomGenerator.Next(0, 100)) / 122 + 0.1;
var point = edgeLine.GetPointOn(offset);
//Calculate offsets
var dx = e.v2.Point.x - e.v1.Point.x;
var dy = e.v2.Point.y - e.v1.Point.y;
//Note swapping offsets for X and Y.
var offsetX = Math.Abs(dx) / (dy);
var offsetY = Math.Abs(dy) / (dx * -1);
//Calculate the maximum endpoint for the new node.
var endPoint = new C2DPoint(offsetX * maxOffset + point.x, offsetY * maxOffset + point.y);
var newLine = new C2DLine(point, endPoint);
var otherVertex1 = e.v1;
var otherVertex2 = e.v2;
var otherEdge1 = otherVertex1.GetOther(e).CreateLine();
var otherEdge2 = otherVertex2.GetOther(e).CreateLine();
//Compare with both other edges, to check if the new vertex would still result in a convex polygon.
//If not, update the maximum offset for the new vertex
if (otherVertex1.GetOther(e) != otherVertex2.GetOther(e))
{
var intersections = new List<C2DPoint>();
otherEdge1.GrowFromCentre(100000000);//Hack: to check if they intersect. The library does not support rays in this case
if (newLine.Crosses(otherEdge1, intersections))
{
var newEndpoint = intersections.Single();
newLine = new C2DLine(point, newEndpoint);
}
intersections = new List<C2DPoint>();
otherEdge2.GrowFromCentre(100000000); //Hack: to check if they intersect. The library does not support rays in this case
if (newLine.Crosses(otherEdge2, intersections))
{
var newEndpoint = intersections.Single();
newLine = new C2DLine(point, newEndpoint);
}
}
//Select a random point on the line (which is bound)
var newlineOffset = Convert.ToDouble(RandomGenerator.Next(0, 100)) / 122+0.1;
var newPoint = newLine.GetPointOn(offset);
var newVertex = new Vertex() { Point = newPoint };
//Indexof might be very slow? Note this is just used for the creation of a testvertex
gm.AddVertexAt(newVertex, gm.Vertices.IndexOf(otherVertex2));
gm.DestroyEdge(e);//Unregister the old edge
result.Add(gm.CreateEdge(otherVertex1, newVertex)); //Add the two new ones
result.Add(gm.CreateEdge(newVertex, otherVertex2)); // :)
return result;
}
