private List <RiverNode> GenerateDownslopes(MapArray <int> bitmask)
{
var simplex = new Simplex2D(52562);
MapArray <float> weights = new MapArray <float>(1000.0f);
var rivernet = new List <RiverNode>();
var node_lookup = new Dictionary <GBTCorner, RiverNode>();
var queue = new BinaryMinHeap <QueueElement <RiverNode> >();
// Assign weights to each land vertex and add coast vertices to the queue.
foreach (KeyValuePair <GBTCorner, int> kvp in bitmask.GetCornerEnumerator())
{
if ((kvp.Value & 1) > 0)
{
weights[kvp.Key] = simplex.GetFractalNoise(4.0f * kvp.Key.position / Radius);
if ((kvp.Value & 2) > 0)
{
RiverNode node = new RiverNode(kvp.Key);
queue.Push(new QueueElement <RiverNode>(weights[kvp.Key], node));
rivernet.Add(node);
node_lookup[kvp.Key] = node;
}
}
}
while (queue.Count > 0)
{
RiverNode node = queue.Pop().value;
GBTCorner lowest = new GBTCorner(-1);
float lowest_weight = 999.0f;
// Find the neighboring land node with the lowest weight which has not already
// been added to the network.
foreach (GBTCorner adjacent in node.Vertex.GetAdjacent())
{
if (CheckValidAdjacent(node, adjacent, bitmask, node_lookup) && weights[adjacent] < lowest_weight)
{
lowest_weight = weights[adjacent];
lowest = adjacent;
}
}
// Add the lowest node to the network, and push it and the into the queue.
if (lowest.isValid())
{
var new_node = new RiverNode(lowest);
new_node.Downslope = node;
if (node.Left == null)
{
node.Left = new_node;
// If the node hasn't been filled, add it to the queue again, but with a lower weight.
weights[node.Vertex] += 0.05f;
queue.Push(new QueueElement <RiverNode>(weights[node.Vertex], node));
}
else if (node.Right == null)
{
node.Right = new_node;
}
node_lookup[lowest] = new_node;
queue.Push(new QueueElement <RiverNode>(weights[lowest], new_node));
}
}
return(rivernet);
}
