/// <summary>
/// Paces back and forth along a platform, waiting at either end.
/// </summary>
public void Update(GameTime gameTime)
{
float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
// Calculate tile position based on the side we are walking towards.
float posX = Position.X + localBounds.Width / 2 * (int)direction;
int tileX = (int)Math.Floor(posX / Tile.Width) - (int)direction;
int tileY = (int)Math.Floor(Position.Y / Tile.Height);
if (waitTime > 0)
{
// Wait for some amount of time.
waitTime = Math.Max(0.0f, waitTime - (float)gameTime.ElapsedGameTime.TotalSeconds);
if (waitTime <= 0.0f)
{
// Then turn around.
direction = (FaceDirection)(-(int)direction);
}
}
else
{
// If we are about to run into a wall or off a cliff, start waiting.
if (Level.GetCollision(tileX + (int)direction, tileY - 1) == TileCollision.Impassable ||
Level.GetCollision(tileX + (int)direction, tileY) == TileCollision.Passable)
{
waitTime = MaxWaitTime;
}
else
{
// Move in the current direction.
Vector2 velocity = new Vector2((int)direction * MoveSpeed * elapsed, 0.0f);
position = position + velocity;
}
}
}
/// <summary>
/// Detects and resolves all collisions between the player and his neighboring
/// tiles. When a collision is detected, the player is pushed away along one
/// axis to prevent overlapping. There is some special logic for the Y axis to
/// handle platforms which behave differently depending on direction of movement.
/// </summary>
private void HandleCollisions()
{
// Get the player's bounding rectangle and find neighboring tiles.
Rectangle bounds = BoundingRectangle;
int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width);
int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1;
int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height);
int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1;
// Reset flag to search for ground collision.
isOnGround = false;
// For each potentially colliding tile,
for (int y = topTile; y <= bottomTile; ++y)
{
for (int x = leftTile; x <= rightTile; ++x)
{
// If this tile is collidable,
TileCollision collision = Level.GetCollision(x, y);
if (collision != TileCollision.Passable)
{
// Determine collision depth (with direction) and magnitude.
Rectangle tileBounds = Level.GetBounds(x, y);
Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds);
if (depth != Vector2.Zero)
{
float absDepthX = Math.Abs(depth.X);
float absDepthY = Math.Abs(depth.Y);
// Resolve the collision along the shallow axis.
if (absDepthY < absDepthX || collision == TileCollision.Platform)
{
// If we crossed the top of a tile, we are on the ground.
if (previousBottom <= tileBounds.Top)
{
isOnGround = true;
}
// Ignore platforms, unless we are on the ground.
if (collision == TileCollision.Impassable || IsOnGround)
{
// Resolve the collision along the Y axis.
Position = new Vector2(Position.X, Position.Y + depth.Y);
// Perform further collisions with the new bounds.
bounds = BoundingRectangle;
}
}
else if (collision == TileCollision.Impassable) // Ignore platforms.
{
// Resolve the collision along the X axis.
Position = new Vector2(Position.X + depth.X, Position.Y);
// Perform further collisions with the new bounds.
bounds = BoundingRectangle;
}
}
}
}
}
// Save the new bounds bottom.
previousBottom = bounds.Bottom;
}
