// obtain the level 0 node that associates with the given pos.
public static BlockVectorNode readNode(IntVector3 atpos, BlockVectorNode root)
{
// calculate the index of the child in which the split will happen.
int ind = 0;
BlockVectorNode cur = root;
IntVector3 nodeCenterPos = IntVector3.Zero;
while (cur.pos.w != 0)
{
nodeCenterPos.x = cur.pos.x + cur.logicalSize / 2;
nodeCenterPos.y = cur.pos.y + cur.logicalSize / 2;
nodeCenterPos.z = cur.pos.z + cur.logicalSize / 2;
ind = ((atpos.x >= nodeCenterPos.x) ? 1 : 0) |
((atpos.y >= nodeCenterPos.y) ? 2 : 0) |
((atpos.z >= nodeCenterPos.z) ? 4 : 0);
if (cur.isLeaf)
{
cur.Split();
}
cur = cur.children[ind] as BlockVectorNode;
}
return(cur);
}
// this function should only be used by the root node.
public BlockVectorNode reroot(IntVector3 atpos)
{
if (covers(atpos) == false)
{
// make a new node that can cover atpos
IntVector4 newRootPos = new IntVector4(pos.XYZ, pos.w + 1);
int maskX = 0;
int maskY = 0;
int maskZ = 0;
if (atpos.x < pos.x)
{
maskX = 1;
}
if (atpos.y < pos.y)
{
maskY = 1;
}
if (atpos.z < pos.z)
{
maskZ = 1;
}
newRootPos.x -= maskX * logicalSize;
newRootPos.y -= maskY * logicalSize;
newRootPos.z -= maskZ * logicalSize;
BlockVectorNode newRoot = new BlockVectorNode(newRootPos, null, 0);
this.parent = newRoot;
newRoot.Split();
int thisOctant = maskX + (maskY << 1) + (maskZ << 2);
newRoot.children[thisOctant] = null;
newRoot.children[thisOctant] = this;
this.octant = thisOctant;
return(newRoot.reroot(atpos));
}
return(this);
}