public void Move(Unit unit, double x, double y)
{
// see which cell it was in
int oldCellX = (int) (unit.X/CELL_SIZE);
int oldCellY = (int) (unit.Y/CELL_SIZE);
// see which cell we are moving to
int newCellX = (int)(x / CELL_SIZE);
int newCellY = (int)(y / CELL_SIZE);
unit.X = x;
unit.Y = y;
// if it didn't change cells, we're done
if (oldCellX == newCellX && oldCellY == newCellY)
return;
// unlink it from the list of its old ell
if (unit.Prev != null)
unit.Prev.Next = unit.Next;
if (unit.Next != null)
unit.Next.Prev = unit.Prev;
// if it's the head of a list, remove it
if (_cells[oldCellX, oldCellX] == unit)
_cells[oldCellX, oldCellY] = unit.Next;
// add it back to the grid at its new cell
Add(unit);
}
// O(n^2) checks!
public void HandleMeleeNonOptimized(Unit[] units, int numUnits)
{
for (int a = 0; a < numUnits - 1; a++)
{
for (int b = a+1; b < numUnits; b++)
{
// basic collision detection
if (units[a].X == units[b].X && units[a].Y == units[b].Y)
HandleAttack(units[a], units[b]);
}
}
}
public void Add(Unit unit)
{
// determine which grid cell it's in
// Dividing by cell size conversts world coordinates to cell space
// Casting using int truncates the fractional part, so we get the cell index
int cellX = (int) (unit.X/CELL_SIZE);
int cellY = (int) (unit.Y/CELL_SIZE);
// add to the front of the list for the cell it's in
unit.Prev = null;
unit.Next = _cells[cellX, cellY];
_cells[cellX, cellY] = unit;
if (unit.Next != null)
unit.Next.Prev = unit;
}
// instead of doing O(n^2) checks, we only do
private void HandleCell(Unit unit)
{
Unit other = unit.Next;
while (other != null)
{
if (unit.X == other.X && unit.Y == other.Y)
HandleAttack(unit, other);
}
}
private void HandleAttack(Unit unit, Unit other)
{
Console.WriteLine("{0} attacks {1}!", unit, other);
}
