/PhysicsEngines/Bullet/Helpers.cs

using BulletXNA.BulletCollision;

using Delta.Rendering.Models;

using Delta.Utilities.Datatypes;

using BulletVector3 = Microsoft.Xna.Framework.Vector3;

using BulletMatrix = Microsoft.Xna.Framework.Matrix;



namespace Delta.PhysicsEngines.Bullet

{

	/// <summary>

	/// Helpers class used into the library.

	/// </summary>

	public static class Helpers

	{

		#region CreateFrom (Static)

		/// <summary>

		/// Helper method used for creation of Bullet TriangleMeshShape by 

		/// populating data with vertices and indices gathered from out Mesh.

		/// </summary>

		/// <param name="mesh">The mesh to get data from.</param>

		/// <param name="localSpaceMatrix">The local space matrix.</param>

		/// <param name="invertTriangles">

		/// if set to <c>true</c> we invert winding order of triangles.

		/// </param>

		/// <returns></returns>

		public static TriangleMeshShape CreateFrom(Mesh mesh,

			Matrix localSpaceMatrix, bool invertTriangles)

		{

			// extract the data from the physics mesh

			TriangleMesh triangleMesh = new TriangleMesh(true, false);



			// apply the local transform of the mesh so we get correct coordinates

			Matrix TransMat = localSpaceMatrix;



			ushort[] indices = mesh.Geometry.Data.Indices;



			for (int i = 0; i < mesh.Geometry.Data.NumberOfUsedVertices; i += 3)

			{

				Vector vertex0 = Vector.Transform(

					mesh.Geometry.Data.GetPosition(i), TransMat);



				Vector vertex1 = Vector.Transform(

					mesh.Geometry.Data.GetPosition(i + 1), TransMat);



				Vector vertex2 = Vector.Transform(

					mesh.Geometry.Data.GetPosition(i + 2), TransMat);



				triangleMesh.AddTriangle(

					BulletDatatypesMapping.Convert(vertex0),

					BulletDatatypesMapping.Convert(vertex1),

					BulletDatatypesMapping.Convert(vertex2));



				// add Indices too

				if (invertTriangles)

				{

					triangleMesh.AddIndex(indices[i + 2]);

					triangleMesh.AddIndex(indices[i + 1]);

					triangleMesh.AddIndex(indices[i]);

				}

				else

				{

					triangleMesh.AddIndex(indices[i]);

					triangleMesh.AddIndex(indices[i + 1]);

					triangleMesh.AddIndex(indices[i + 2]);

				}

			}



			// Now create shape and return

			return new TriangleMeshShape(triangleMesh);

		}

		#endregion



		#region GetCenter (Static)

		/// <summary>

		/// 

		/// </summary>

		/// <param name="bbox"></param>

		/// <returns></returns>

		public static BulletVector3 GetCenter(BoundingBox bbox)

		{

			return new BulletVector3(

				(bbox.Max.X + bbox.Min.X) * 0.5f,

				(bbox.Max.Y + bbox.Min.Y) * 0.5f,

				(bbox.Max.Z + bbox.Min.Z) * 0.5f);

		}

		#endregion

	}

}