/Samples/CarGame2D/Track.cs

using DeltaEngine.Content;

using DeltaEngine.Datatypes;

using DeltaEngine.Rendering2D;



namespace CarGame2D

{

	/// <summary>

	/// Track class for the game, handles painting and helps with collision checking.

	/// </summary>

	public class Track : Entity2D

	{

		public Track(Vector2D[] positions)

		{

			Positions = positions;

			Material = new Material(ShaderFlags.Position2DTextured, "TrackImage");

			OnDraw<TrackRenderer>();

			CenterAllPositions(positions);

			TrackStart = positions[0];

			CalculateInnerAndOuterBounds(positions);

		}



		public Vector2D[] Positions { get; private set; }

		public Material Material { get; private set; }



		private static void CenterAllPositions(Vector2D[] positions)

		{

			Vector2D center = positions[0];

			for (int index = 1; index < positions.Length; index++)

				center += positions[index];

			center /= positions.Length;

			Vector2D offset = new Vector2D(0.5f, 0.49f) - center;

			for (int index = 0; index < positions.Length; index++)

				positions[index] += offset;

		}



		public Vector2D TrackStart { get; private set; }



		private void CalculateInnerAndOuterBounds(Vector2D[] positions)

		{

			TrackInnerBounds = new Vector2D[positions.Length];

			TrackOuterBounds = new Vector2D[positions.Length];

			for (int index = 0; index < Positions.Length; index++)

			{

				var previousPos = Positions[index - 1 == -1 ? Positions.Length - 1 : index - 1];

				var nextPos = Positions[(index + 1) % Positions.Length];

				var dir = Vector2D.Normalize(nextPos - previousPos);

				var normal = Vector2D.Normalize(dir.Rotate(90));

				TrackOuterBounds[index] = Positions[index] - normal * TrackWidth * 0.5f;

				TrackInnerBounds[index] = Positions[index] + normal * TrackWidth * 0.5f;

			}

		}



		public Vector2D[] TrackInnerBounds { get; private set; }

		public Vector2D[] TrackOuterBounds { get; private set; }

		public const float TrackWidth = 0.12f;

	}

}