internal void AddShip(SpaceShip ship, OctreeNode parent)
{
//// Wallace's hack: if center point of the node
//// is contained in the sphere it will straddle with the children
//// therefore we want to keep it on current node
//var delta = ship.CollisionSphere.Center - this.Center;
//float distSquared = Vector3.Dot(delta, delta);
//bool straddling = distSquared <= ship.CollisionSphere.Radius * ship.CollisionSphere.Radius;
var nodeTop = Math.Abs(this.Center.Y) + HalfSize;
var nodeBottom = Math.Abs(this.Center.Y) - HalfSize;
var nodeLeft = Math.Abs(this.Center.X) - HalfSize;
var nodeRight = Math.Abs(this.Center.X) + HalfSize;
var nodeFront = Math.Abs(this.Center.Z) + HalfSize;
var nodeBack = Math.Abs(this.Center.Z) - HalfSize;
var sphereTop = Math.Abs(ship.CollisionSphere.Center.Y) + ship.CollisionSphere.Radius;
var sphereBottom = Math.Abs(ship.CollisionSphere.Center.Y) - ship.CollisionSphere.Radius;
var sphereLeft = Math.Abs(ship.CollisionSphere.Center.X) - ship.CollisionSphere.Radius;
var sphereRight = Math.Abs(ship.CollisionSphere.Center.X) + ship.CollisionSphere.Radius;
var sphereFront = Math.Abs(ship.CollisionSphere.Center.Z) + ship.CollisionSphere.Radius;
var sphereBack = Math.Abs(ship.CollisionSphere.Center.Z) - ship.CollisionSphere.Radius;
bool straddles = sphereTop >= nodeTop ||
sphereBottom <= nodeBottom ||
sphereLeft <= nodeLeft ||
sphereRight >= nodeRight ||
sphereFront >= nodeFront ||
sphereBack <= nodeBack;
//// Usefull for debug
//_vertices[22] = new VertexPositionColor(ship.CollisionSphere.Center, Color.Black);
//_vertices[23] = new VertexPositionColor(ship.CollisionSphere.Center + new Vector3(0, -ship.CollisionSphere.Radius, 0), Color.Black);
//var center = Vector3.Transform(Center,
//Matrix.CreateTranslation(ship.CollisionSphere.Center));
// Fully contained in existing child node; insert in that subtree
if (!straddles && _depth > 0)
{
int childOctant = 0;
var delta = ship.CollisionSphere.Center - this.Center;
if (delta.X > 0.0f)
{
childOctant += 1;
}
if (delta.Y > 0.0f)
{
childOctant += 2;
}
if (delta.Z > 0.0f)
{
childOctant += 4;
}
Children[childOctant].AddShip(ship, this);
}
else if (straddles) // Straddles
{
ship.OctTreeNode = parent;
ship.ShipNode = parent.Ships.AddLast(ship);
}
else // no children left
{
ship.OctTreeNode = this;
ship.ShipNode = Ships.AddLast(ship);
}
}