MonoGame.Samples/FuelCell/FuelCell.Core/Game/GameObject.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace FuelCell
{
    public class GameObject
    {
        public Model Model { get; set; }
        public Vector3 Position { get; set; }
        public bool IsActive { get; set; }
        public BoundingSphere BoundingSphere { get; set; }

        public GameObject()
        {
            Model = null;
            Position = Vector3.Zero;
            IsActive = false;
            BoundingSphere = new BoundingSphere();
        }

        protected BoundingSphere CalculateBoundingSphere()
        {
            BoundingSphere mergedSphere = new BoundingSphere();
            BoundingSphere[] boundingSpheres;
            int index = 0;
            int meshCount = Model.Meshes.Count;

            boundingSpheres = new BoundingSphere[meshCount];
            foreach (ModelMesh mesh in Model.Meshes)
            {
                boundingSpheres[index++] = mesh.BoundingSphere;
            }

            mergedSphere = boundingSpheres[0];
            if ((Model.Meshes.Count) > 1)
            {
                index = 1;
                do
                {
                    mergedSphere = BoundingSphere.CreateMerged(mergedSphere, boundingSpheres[index]);
                    index++;
                } while (index < Model.Meshes.Count);
            }
            mergedSphere.Center.Y = 0;
            return mergedSphere;
        }

        /// <summary>
        /// Debugging method to draw the bounding sphere of the object.
        /// </summary>
        /// <param name="view">The view matrix from the camera.</param>
        /// <param name="projection">The projection matrix from the camera.</param>
        /// <param name="boundingSphereModel">The GameObject to draw the bounding sphere around.</param>
        internal void DrawBoundingSphere(Matrix view, Matrix projection, GameObject boundingSphereModel)
        {
            Matrix scaleMatrix = Matrix.CreateScale(BoundingSphere.Radius);
            Matrix translateMatrix = Matrix.CreateTranslation(BoundingSphere.Center);
            Matrix worldMatrix = scaleMatrix * translateMatrix;

            foreach (ModelMesh mesh in boundingSphereModel.Model.Meshes)
            {
                foreach (BasicEffect effect in mesh.Effects)
                {
                    effect.World = worldMatrix;
                    effect.View = view;
                    effect.Projection = projection;
                }
                mesh.Draw();
            }
        }
    }
}