protected override void Update(GameTime gameTime)
        {
            GamePadState gamePadState = GamePad.GetState(PlayerIndex.One);

            if (gamePadState.Buttons.Back == ButtonState.Pressed)
            {
                this.Exit();
            }

            MouseState    mouseState = Mouse.GetState();
            KeyboardState keyState   = Keyboard.GetState();

            quatCam.Update(mouseState, keyState, gamePadState);

            base.Update(gameTime);
        }
        protected override void Update(GameTime gameTime)
        {
            GamePadState gamePadState = GamePad.GetState(PlayerIndex.One);

            if (gamePadState.Buttons.Back == ButtonState.Pressed)
            {
                this.Exit();
            }

            MouseState    mouseState = Mouse.GetState();
            KeyboardState keyState   = Keyboard.GetState();

            quatCam.Update(mouseState, keyState, gamePadState);

            if ((keyState.IsKeyDown(Keys.Space)) || (gamePadState.Buttons.A == ButtonState.Pressed))
            {
                CreateExplosionVertices((float)gameTime.TotalGameTime.TotalMilliseconds);
            }

            base.Update(gameTime);
        }
        protected override void Update(GameTime gameTime)
        {
            GamePadState gamePadState = GamePad.GetState(PlayerIndex.One);

            if (gamePadState.Buttons.Back == ButtonState.Pressed)
            {
                this.Exit();
            }

            MouseState    mouseState = Mouse.GetState();
            KeyboardState keyState   = Keyboard.GetState();

            quatCam.Update(mouseState, keyState, gamePadState);

            billboardGC.camForward       = quatCam.Forward;
            billboardGC.camPosition      = quatCam.Position;
            billboardGC.viewMatrix       = quatCam.ViewMatrix;
            billboardGC.projectionMatrix = quatCam.ProjectionMatrix;

            base.Update(gameTime);
        }