public HeightmapQuadTreeNode GetOrAdd(int index, bool doSpread)
{
HeightmapQuadTreeNode result;
if (Children[index] == null)
{
var rect = Range;
rect.Width /= 2;
rect.Height /= 2;
if ((index % 2) == 1)
{
rect.X += rect.Width;
}
if (index > 1)
{
rect.Y += rect.Height;
}
result = new HeightmapQuadTreeNode(this, rect);
result.ParentInd = index;
Children[index] = result;
doSpread = true;
}
else
{
result = Children[index];
}
if (doSpread)
{
if (Parent != null)
{
//find adjacent quad to add to.
//for example if we are in index 0 (top left), make sure there is:
// - a subdivision in the top right (1) of the tile to our left,
// - a subdivision in the bottom left (2) of the tile above us,
// - a subdivision in the bottom right (3) of the tile above and left
//index 1 (top right
switch (index)
{
case 0: //top left
{
var left = result.FindOrCreateQuadInDirection(3);
var up = result.FindOrCreateQuadInDirection(0);
if (up != null)
{
up.FindOrCreateQuadInDirection(3);
}
break;
}
case 1: //top right
{
var right = result.FindOrCreateQuadInDirection(1);
var up = result.FindOrCreateQuadInDirection(0);
if (up != null)
{
up.FindOrCreateQuadInDirection(1);
}
break;
}
case 2: //bottom left
{
var left = result.FindOrCreateQuadInDirection(3);
var bottom = result.FindOrCreateQuadInDirection(2);
if (bottom != null)
{
bottom.FindOrCreateQuadInDirection(3);
}
break;
}
case 3: //bottom right
{
var right = result.FindOrCreateQuadInDirection(1);
var bottom = result.FindOrCreateQuadInDirection(2);
if (bottom != null)
{
bottom.FindOrCreateQuadInDirection(1);
}
break;
}
}
}
}
return(result);
}
public HeightmapQuadTreeNode(HeightmapQuadTreeNode parent, Rectangle range)
{
Parent = parent;
Range = range;
MipLevel = (parent?.MipLevel ?? 6) - 1;
}
