Xna c# picking model with Ray mouse cursor select the wrong model

Question

i made a small 3D game and i just try to apply a basic sample from here : http://rbwhitaker.wikidot.com/picking for picking model by the mouse cursor. For that i use the Ray object and check if some model intersect my Ray. But i don't know why, the model object target by my cursor is always offset to the left.there is a shift difference.

Here is the code i use.

// Update Ray cursor each frame in the Update loop function

public void UpdateRayCursor()
        {
            Vector3 nearPoint = new Vector3(Globals.mouseState.Position.ToVector2(), 0);
            Vector3 farPoint = new Vector3(Globals.mouseState.Position.ToVector2(), 1);

            nearPoint = graphic.GraphicsDevice.Viewport.Unproject(nearPoint, CameraNode.Camera.Projection, (Matrix)CameraNode.View, Matrix.Identity);
            farPoint = graphic.GraphicsDevice.Viewport.Unproject(farPoint, CameraNode.Camera.Projection, (Matrix)CameraNode.View, Matrix.Identity);

            Vector3 direction = farPoint - nearPoint;
            direction.Normalize();

            Ray = new Microsoft.Xna.Framework.Ray(
                nearPoint
                ,
                direction
                );
        }

// check if a model is target by the Ray

public void UpdateIntersectSceneRay()
    {
        float? nearestDistance = 0f;
        bool findModelTarget = false;
        foreach (var bdgToCheck in ListBlocksSelectable)
        {
            //Check if the boundingBox intersect with the ray
            var checkIntersectDistance = _mainPlayer.Ray.Intersects(bdgToCheck);
            if (checkIntersectDistance != null)
            {
                if ((float)checkIntersectDistance < (float)nearestDistance || nearestDistance == 0)
                {
                    nearestDistance = checkIntersectDistance;
                    _mainPlayer.ItemFocusByReticle = item;
                    findModelTarget = true;
                }
            }
        }
        if(!findModelTarget)
        {
            _mainPlayer.ItemFocusByReticle = null;
        }

    }

Some people have some idea why ? i use monogame library with XNA. Thank you in advance

Answer 1

It's ok , i finally find the solution by myself. Is because when i try to get the mouse position. It's not exactly the center of the screen which must match the player cursor. I must use like this :

Vector2 posCursor = new Vector2(
            graphic.GraphicsDevice.Viewport.Width/2,
            graphic.GraphicsDevice.Viewport.Height/2
            );
        Vector3 nearPoint = new Vector3(posCursor, 0.0f);
        Vector3 farPoint = new Vector3(posCursor, 1.0f);