// A broad phase collision detection method utilizing a spatial grid
private void CheckCollisions_Grid(float timeStep)
{
List <int> keys = grid.GetKeys(); // get the list of existing cells
// For each cell in the grid
foreach (int key in keys)
{
// Get a list of balls in that cell
List <Ball> ballsInCell = grid.GetObjectsInCell(key);
// If there is more than one ball,
if (ballsInCell.Count > 1)
{
// For each ball in the cell
for (int i = 0; i < ballsInCell.Count - 1; i++)
{
// Check whether it's colliding with another ball
for (int j = i + 1; j < ballsInCell.Count; j++)
{
if (ballsInCell[i].IsCollidingWith(ballsInCell[j]))
{
CollisionResolve(ballsInCell [i], ballsInCell [j]); // Trigger collision resolution
}
}
}
}
}
}