private void SplitNode(Node node)
{
if (node == null || node.Split)
return;
node.Split = true;
if (node.Visible && node.LeftChild != null)
{
node.LeftChild.Visible = true;
node.RightChild.Visible = true;
}
if (node.BaseNeighbor != null && node.BaseNeighbor.BaseNeighbor != node)
{
SplitNode(node.BaseNeighbor);
vertexCounter++;
}
SplitNode(node.BaseNeighbor);
if (node.LeftNeighbor != null)
{
if (node.LeftNeighbor.BaseNeighbor == node)
node.LeftNeighbor.BaseNeighbor = node.LeftChild;
else
node.LeftNeighbor.RightNeighbor = node.LeftChild;
}
if (node.RightNeighbor != null)
{
if (node.RightNeighbor.BaseNeighbor == node)
node.RightNeighbor.BaseNeighbor = node.RightChild;
else
node.RightNeighbor.LeftNeighbor = node.RightChild;
}
if (node.LeftChild != null)
{
node.LeftChild.BaseNeighbor = node.LeftNeighbor;
node.RightChild.BaseNeighbor = node.RightNeighbor;
node.LeftChild.LeftNeighbor = node.RightChild;
node.RightChild.RightNeighbor = node.LeftChild;
if (node.BaseNeighbor != null)
{
node.RightChild.LeftNeighbor = node.BaseNeighbor.LeftChild;
node.LeftChild.RightNeighbor = node.BaseNeighbor.RightChild;
}
}
}
private void UpdateNode(Node node, Point p0, Point p1, Point a)
{
node.Visible = true;
if (FrustumCullingEnabled && ViewFrustum.Contains(GetBoundingBox(node)) == ContainmentType.Disjoint)
{
node.Visible = false;
return;
}
Point p = GetMidpoint(p0, p1);
int width = Math.Abs(p0.X - p1.X) + Math.Abs(p0.Y - p1.Y);
float distanceSquared = (CameraPosition - new Vector3(p.X, GetHeight(p) * Bumpiness, -p.Y)).LengthSquared();
bool split = SplitCheck(node, width, distanceSquared);
if (!node.Split && split)
{
SplitNode(node);
vertexCounter++;
}
else if (node.Split && !split && CanMerge(node) && CanMerge(node.BaseNeighbor))
{
MergeNode(node);
MergeNode(node.BaseNeighbor);
vertexCounter--;
}
if (node.Split && node.LeftChild != null)
{
UpdateNode(node.LeftChild, a, p0, p);
UpdateNode(node.RightChild, p1, a, p);
}
}
private void MergeNode(Node node)
{
if (node == null)
return;
node.Split = false;
if (node.LeftChild != null)
{
node.LeftNeighbor = node.LeftChild.BaseNeighbor;
node.RightNeighbor = node.RightChild.BaseNeighbor;
}
if (node.LeftNeighbor != null)
{
if (node.LeftNeighbor.BaseNeighbor == node.LeftChild)
node.LeftNeighbor.BaseNeighbor = node;
else
node.LeftNeighbor.RightNeighbor = node;
}
if (node.RightNeighbor != null)
{
if (node.RightNeighbor.BaseNeighbor == node.RightChild)
node.RightNeighbor.BaseNeighbor = node;
else
node.RightNeighbor.LeftNeighbor = node;
}
}
private bool SplitCheck(Node node, int width, float distanceSquared)
{
float error = node.Error;
if (node.BaseNeighbor != null && node.BaseNeighbor.BaseNeighbor == node)
error = MathHelper.Max(error, node.BaseNeighbor.Error);
float maxDistance = error * Bumpiness * Quality * width;
float maxDistanceSquared = maxDistance * maxDistance;
return distanceSquared < maxDistanceSquared;
}
private void InitializeTerrain()
{
levels = (int)Math.Log(Size - 1, 2) * 2 - 1;
bottomLeft = new Point(0, 0);
bottomRight = new Point(Size - 1, 0);
topLeft = new Point(0, Size - 1);
topRight = new Point(Size - 1, Size - 1);
rootLeft = InitializeNode(bottomRight, topLeft, bottomLeft, 0);
rootRight = InitializeNode(topLeft, bottomRight, topRight, 0);
rootLeft.BaseNeighbor = rootRight;
rootRight.BaseNeighbor = rootLeft;
}
private Node InitializeNode(Point p0, Point p1, Point a, int level)
{
Node node = new Node();
Point p = GetMidpoint(p0, p1);
node.Error = Math.Abs(GetError(p0, p, p1));
node.BoundingBox = GetBoundingBox(p0, p1, a);
if (level < levels)
{
node.LeftChild = InitializeNode(a, p0, p, level + 1);
node.RightChild = InitializeNode(p1, a, p, level + 1);
if (node.LeftChild.Error > node.Error)
node.Error = node.LeftChild.Error;
if (node.RightChild.Error > node.Error)
node.Error = node.RightChild.Error;
node.BoundingBox = BoundingBox.CreateMerged(node.LeftChild.BoundingBox, node.RightChild.BoundingBox);
}
else
node.BoundingBox = GetBoundingBox(p0, p1, a);
return node;
}
private BoundingBox GetBoundingBox(Node node)
{
Vector3 min = node.BoundingBox.Min;
Vector3 max = node.BoundingBox.Max;
if (!HeightmapEnabled || Bumpiness == 0.0f)
{
min.Y = HeightOffset - 1.0f;
max.Y = HeightOffset + 1.0f;
}
else
{
min.Y *= Bumpiness;
max.Y *= Bumpiness;
}
if (min.Y > max.Y)
{
float y = min.Y;
min.Y = max.Y;
max.Y = y;
}
return new BoundingBox(min, max);
}
private void CollectIndices(Node node, Point p0, Point p1, Point a)
{
if (node != null && !node.Visible)
return;
if (node == null || !node.Split)
{
Indices.Add(GetIndex(p0));
Indices.Add(GetIndex(a));
Indices.Add(GetIndex(p1));
}
else
{
Point p = GetMidpoint(p0, p1);
CollectIndices(node.LeftChild, a, p0, p);
CollectIndices(node.RightChild, p1, a, p);
}
}
private bool CanMerge(Node node)
{
return (node == null || node.LeftChild == null || (!node.LeftChild.Split && !node.RightChild.Split));
}