A method of generating a three-dimensional (3D) image includes displaying a two-dimensional (2D) image of at least a portion of a (3D) object on a display surface. The method includes detecting a tilt angle of a digital pen while the digital pen is used to contact at least one location on a first surface of the (2D) image on the display surface, wherein the detected tilt angle represents a surface property of the first surface at the at least one location. The method includes generating a (3D) image of the object based on the detected tilt angle.