Mouse 2D to Screen 3D

        public static Vector3 GetScreenCoordinates(MouseState mouseState, Viewport viewport, Vector3 target, Matrix projection, Matrix view, Matrix world, float dimension = 1f, bool ceiling = true)
        {
            Vector3 pos = Vector3.Zero;

            Vector3 pos0 = new Vector3(mouseState.X, mouseState.Y, 0);
            Vector3 pos1 = new Vector3(mouseState.X, mouseState.Y, 1);

            pos0 = viewport.Unproject(pos0, projection, view, world);
            pos1 = viewport.Unproject(pos1, projection, view, world);

            Ray ray = new Ray(pos0, pos1 - pos0);
            float? depth = ray.Intersects(new Plane(Vector3.UnitY, 0));

            if (depth != null)
            {
                Vector3 ms_world_pos = (pos0 + (pos1 - pos0) * depth.Value);

                bool XN = (ms_world_pos.X < 0);
                bool ZN = (ms_world_pos.Z < 0);

                ms_world_pos.X = (int)(ms_world_pos.X / dimension);
                ms_world_pos.Y = (int)(ms_world_pos.Y / dimension);
                ms_world_pos.Z = (int)(ms_world_pos.Z / dimension);

                ms_world_pos.X += XN ? -0.5f : 0.5f;
                ms_world_pos.Y += 0;
                ms_world_pos.Z += ZN ? -0.5f : 0.5f;

                ms_world_pos *= dimension;

                pos = ms_world_pos;
            }

            if (ceiling)
            {
                pos.X = (float)Math.Ceiling(pos.X);
                pos.Y = (float)Math.Ceiling(pos.Y);
                pos.Z = (float)Math.Ceiling(pos.Z);
            }

            return pos;
        }