public Matrix4d pick(double x, double y, double width, double height, int[] viewport) {
        return pick(x, y, width, height, viewport, this);
    }
public Matrix4d pick ( double x , double y , double width , double height , int [ ] viewport ) { return pick ( x , y , width , height , viewport , this ) ; }
Apply a picking transformation to this matrix using the given window coordinates <code>(x, y)</code> as the pick center
and the given <code>(width, height)</code> as the size of the picking region in window coordinates.

@param x
the x coordinate of the picking region center in window coordinates
@param y
the y coordinate of the picking region center in window coordinates
@param width
the width of the picking region in window coordinates
@param height
the height of the picking region in window coordinates
@param viewport
the viewport described by <code>[x, y, width, height]</code>
@return this