Patent Publication Number: US-2007101277-A1

Title: Navigation apparatus for three-dimensional graphic user interface

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority from Korean Patent Application No. 10-2005-0101511 filed on Oct. 26, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Apparatuses consistent with the present invention relate to navigation in a graphical user interface, and more particularly, to navigation for movement in a z-axis in a three-dimensional graphic user interface.  
      2. Description of the Related Art  
      In general, graphic user interfaces (hereinafter, referred to as GUIs) are used in digital apparatuses to conveniently use the digital apparatuses and to rapidly and intuitively provide information to a user. The user can move a pointer using an input device, such as a key pad, a keyboard, or a mouse, and select an object indicated by the pointer, thereby instructing the digital apparatus to perform a desired operation.  
      The GUIs are mainly classified into two-dimensional GUIs and three-dimensional GUIs. The two-dimensional GUI is two-dimensional and static, and the three-dimensional GUI is three-dimensional and dynamic. Therefore, as compared with the two-dimensional GUI, the three-dimensional GUI can communicate information to the user more visually, and further satisfy the sensitivity of the user. For this reason, two-dimensional GUIs used in digital apparatuses have been replaced with three-dimensional GUIs.  
      Although the two-dimensional GUIs of digital apparatuses have been replaced with the three-dimensional GUIs, a related digital apparatus can merely navigate the two-dimensional GUI by using, for example, four directional keys or a joystick.  
      A problem in the related art causes a user to be confused by navigating the three-dimensional GUI using a two-dimensional input device, and is a restriction in developing various three-dimensional GUIs. In order to solve the above-mentioned problem, various techniques have been proposed (for example, Korean Patent Unexamined Publication No. 2004-0090133, titled “METHOD OF ALLOCATING KEY BUTTONS OF PORTABLE TERMINAL FOR CONTROLLING THREE-DIMENSIONAL IMAGE”). However, the above-mentioned disclosures are not enough to completely solve the problem.  
      Therefore, an input device capable of navigating a three-dimensional GUI is needed.  
     SUMMARY OF THE INVENTION  
      Exemplary embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an exemplary embodiment of the present invention may not overcome any of the problems described above.  
      The present invention is made to address the above-mentioned problems, and it is an aspect of the invention to provide a navigation apparatus for a three-dimensional graphic user interface.  
      However, the invention is not limited to the above-mentioned aspect, and other aspects of the invention not described herein will become clear to those skilled in the art upon review of the exemplary embodiments.  
      According to an aspect of the present invention, there is provided a navigation apparatus for a three-dimensional graphic user interface including an input unit that includes a first directional key that is used for directional movement in a plane and has a first thickness and a second directional key that is used for directional movement along an axis orthogonal to the plane and has a second thickness different from the first thickness; and an object control unit that controls directional movement corresponding to one of the first and second directional keys selected by a user.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:  
       FIG. 1  is a diagram illustrating the overall structure of a three-dimensional graphic user interface according to an exemplary embodiment of the present invention;  
       FIG. 2  is a block diagram illustrating a navigation apparatus for a three-dimensional graphic user interface according to an exemplary embodiment of the present invention;  
       FIG. 3  is a diagram illustrating the arrangement of first and second key input units according to an exemplary embodiment of the present invention and a cross-sectional view taken along the line III-III′;  
       FIG. 4  is a diagram illustrating the arrangement of first and second key input units according to another exemplary embodiment of the present invention and a cross-sectional view taken along the line IV-IV′;  
       FIG. 5  is a diagram illustrating the arrangement of first and second key input units according to still another exemplary embodiment of the present invention and a cross-sectional view taken along the line V-V′;  
       FIG. 6  is a diagram illustrating the arrangement of first and second key input units according to yet another exemplary embodiment of the present invention and a cross-sectional view taken along the line VI-VI′;  
       FIGS. 7A  to  7 D are diagrams illustrating an example of a screen provided by the navigation apparatus for a three-dimensional graphic user interface according to the exemplary embodiment of the present invention; and  
       FIG. 8  is a flowchart illustrating a navigation process performed in the navigation apparatus for a three-dimensional graphic user interface according to the exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION  
      Advantages and features of the present invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of the exemplary embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. Like reference numerals refer to like elements throughout the specification.  
      Hereinafter, a navigation apparatus for a three-dimensional graphic user interface according to exemplary embodiments of the present invention will be described below with reference to block diagrams and flowcharts of the accompanying drawings. It will be understood that blocks in the accompanying block diagrams and combinations of steps in flow charts can be performed by computer program instructions. These computer program instructions can be provided to processors of, for example, general-purpose computers, special-purpose computers, and programmable data processing apparatuses. Therefore, the instructions performed by the computer or a processor of the programmable data processing apparatus create means for executing functions described in the blocks in block diagrams or the steps in the flow charts. The computer program instructions can be stored in a computer usable memory or a computer readable memory of the computer or the programmable data processing apparatus in order to realize the functions in a specific manner. Therefore, the instructions stored in the computer usable memory or the computer readable memory can manufacture products including the instruction means for performing the functions described in the blocks in the block diagrams or the steps in the flow charts. Also, the computer program instructions can be loaded into the computer or the computer programmable data processing apparatus. Therefore, a series of operational steps are performed in the computer or the programmable data processing apparatus to generate a process executed by the computer, which makes is possible for the instructions operating the computer or the programmable data processing apparatus to provide steps of executing the functions described in the blocks of the block diagrams or the steps of the flow charts.  
      Each block or each step may indicate a portion of a code, a module, or a segment including one or more executable instructions for performing a specific logical function (or functions). It should be noted that, in some modifications of the invention, the functions described in the blocks or the steps may be generated in a different order. For example, two blocks or steps continuously shown may actually be performed at the same time, or they may sometimes be performed in reverse order according to the corresponding functions.  
      Before a navigation apparatus for a three-dimensional graphic user interface (hereinafter, referred to as a navigation apparatus) according to an exemplary embodiment of the invention is described, a three-dimensional graphic user interface provided in the navigation apparatus will be briefly described below.  
       FIG. 1  illustrates the overall configuration of a three-dimensional graphic user interface provided in a navigation apparatus according to an exemplary embodiment of the present invention.  
      The three-dimensional graphic user interface is a user interface (UI) capable of establishing a more dynamic GUI environment on the basis of a three-dimensional environment and motion graphics. The three-dimensional graphic user interface environment includes the following elements: a three-dimensional space  100 ; objects  130 ; a camera view; and a method of arranging objects.  
      A three-dimensional space  100  is a space for establishing the three-dimensional environment, and it may be divided into an active space  110  and an inactive space  120  according to the characteristic of the space. The active space  110  can be used to design a user interface (UI).  
      An object  130  provides information to a user while interacting with the user in the three-dimensional environment. The object  130  includes one or more information surfaces. The information surface means a surface capable of displaying information to be communicated to a user, and information on controllable menu items or information on sub-menu items can be communicated to the user by means of the information surfaces. Two-dimensional information items, such as texts, images, moving pictures, and two-dimensional widgets, can be displayed on the information surfaces. In addition, three-dimensional information, such as three-dimensional icons, can be displayed on the information surfaces.  
      The object  130  can have a polyhedral shape, such as a triangular prism, a square pillar, a hexagonal prism, or a cylinder. A sphere may be assumed to be an example of a polyhedron formed of numerous surfaces. The polyhedral object has attributes, such as an identifier and a size. The polyhedron object has, as surface attributes, a number, a color, transparency, and information on whether a corresponding surface is an information surface. These attributes are not limited to those mentioned above, and a variety of attributes may exist according to application fields.  
      The object  130  can generate a unique motion in the three-dimensional space. For example, the object  130  can rotate on a specified axis at a particular angle and in a specified direction. In addition, the position of the object  130  may be shifted, or the size thereof may increase or decrease.  
      The camera view means a view point in the three-dimensional space. The camera view can move in the three-dimensional space. The movement of the camera view means navigation in the three-dimensional space, which causes motion to be generated in the entire three-dimensional space. The camera view is the main cause of motion in the three-dimensional graphic user interface environment, along with unique motion attributes of the objects.  
      A method of arranging the objects means a method of determining how to manipulate a group of one or more objects in the three-dimensional space, what operation occurs during the manipulation, and how to arrange the objects on a screen.  
       FIG. 2  is a block diagram illustrating a navigation apparatus  200  according to an exemplary embodiment of the present invention.  
      The navigation apparatus  200  according to the exemplary embodiment of the present invention may be composed of a digital apparatus including digital circuits for processing digital data. Examples of the digital device may include a computer, a printer, a scanner, a pager, a digital camera, a facsimile, a digital copying machine, a digital appliance, a digital telephone, a digital projector, a home server, a digital video recorder, a digital TV broadcasting receiver, a digital satellite broadcasting receiver, a set-top box, a personal digital assistance (PDA), and a mobile phone.  
      The navigation apparatus  200  shown in  FIG. 2  includes a generating unit  240 , a storage unit  220 , a display unit  260 , an object control unit  250 , a control unit  230 , and an input unit  210 .  
      The generating unit  240  generates a three-dimensional space composed of an x-axis, a y-axis, and a z-axis and polyhedral objects to be arranged in the three-dimensional space.  
      The storage unit  220  stores information on the three-dimensional space and the polyhedral objects generated by the generating unit  240 , and the attributes of the polyhedral objects. For example, the storage unit  220  stores information on the colors and transparency of the surfaces of the polyhedral objects and information on whether the surfaces of the polyhedral objects are information surfaces. The storage unit  220  may be composed of at least one of a non-volatile memory device, such as a read only memory (ROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), or a flash memory, a volatile memory device, such as a random access memory (RAM), and a storage medium, such as a hard disk drive (HDD), but the storage unit  220  is not limited to the above-mentioned devices.  
      The display unit  260  visually displays the polyhedral object generated by the generating unit  240  and the result processed by the object control unit  250 , which will be described below. The display unit  260  can be composed of an image display device, such as a liquid crystal display device (LCD), a light-emitting diode (LED), an organic light-emitting diode (OLED), or a plasma display panel (PDP), but it is not limited to the above-mentioned devices.  
      The input unit  210  receives input values from a user, and includes a first key input unit  211  for directional movement in an x-y plane and a second key input unit  212  for movement in the z-axis direction. When the keys of the input unit  210  are pushed by the user, the keys generate key signals. The input unit  210  will be described in more detail below with reference to FIGS.  3  to  6 .  
      The control unit  230  connects and controls all the components of the navigation apparatus  200 . For example, the control unit  230  generates instruction codes corresponding to the input values input through the input unit  210  and transmits the generated instruction codes to the object control unit  250 .  
      The object control unit  250  uses the object generated by the generating unit  240  to provide a three-dimensional graphic user interface. More specifically, the object control unit  250  gives the above-mentioned attribute to the object generated by the generating unit  240 , and processes the motion of an object on the basis of the input values input by the user. For example, the object control unit  250  shifts the position of the object, changes the size of the object, or rotates the object. In addition, the object control unit  250  emphasizes the object selected by the user. For example, the object control unit  250  forms a mark in the vicinity of the object selected by the user or changes the size, color and transparency of the selected object to emphasize the object. Alternatively, the object control unit  250  may emphasize the object selected by the user by changing the sizes, colors, and transparency of objects not selected by the user.  
      Next, the input unit  210  of the navigation apparatus  200  according to the exemplary embodiment of the invention will be described with reference to FIGS.  3  to  6 .  
      As described above, the input unit  210  includes the first key input unit  211  for directional movement in the x-y plane and the second key input unit  212  for movement in the z-axis direction.  
      More specifically, the first input key  211  includes a right key, a left key, an up key, and a down key. The right and left keys are used for movement in the positive and negative directions of the x-axis, respectively. The up and down keys are used for movement in the positive and negative directions of the y-axis, respectively. The second key input unit  212  includes keys for movement in the positive and negative directions of the z-axis.  
      The regions  310 ,  320  and  330  in which the first key input unit  211  and the second key input unit  212  are arranged may be formed in such a shape that the user can intuitionally recognize the functions of the directional keys. FIGS.  3  show an example of the arrangement of the regions.  
       FIG. 3  shows a two-dimensionally projected hexahedron having the regions  310 ,  320 , and  330  projected on the surfaces thereof. The hexahedron shown in  FIG. 3  includes the first rectangular region  310 , the second region  320  formed above the first region  310 , and the third region formed on one side of the first region  310 . Among the regions  310 ,  320 , and  330 , the up key  311 , the down key  313 , the left key  312 , and the right key  314  are arranged in the first region  310 , and the keys corresponding to the negative and positive directions of the z-axis are arranged in the second region  320  and the third region  330 , respectively.  
      In this case, the keys  311 ,  312 ,  313 , and  314  arranged in the first region  310  may have the same height such that the user can intuitionally recognize that the keys are used for directional movement in the x-y plane when the user touches the first region  310 .  
      On the other hand, the height of the keys arranged in the second region  320  and the third region  330  may become smaller, as the keys become more distant from the keys arranged in the first region  310 , that is, the first input keys, such that the user can intuitionally recognize that the keys arranged in the second and third regions  320  and  330  are used for movement in the z-axis direction, when touching the second region  320  and the third region  330 . That is, the keys arranged in the second region  320  and the third region  330  may be formed as in the cross section shown in  FIG. 3   
      In an exemplary embodiment, marks  322  and  332  are formed in the keys  321  and  331  respectively arranged in the second region  320  and the third region  330  such that the user can recognize the functions of the keys. For example, a key for movement in the positive direction of the z-axis or a key for movement in the negative direction of the z-axis may be arranged in the second region  320 . When the key  321  for movement in the negative direction of the z-axis is arranged in the second region  320 , an arrow  322  representing the negative direction of the z-axis is marked on the key of the second region  320 , and an arrow  332  representing the positive direction of the z-axis is marked on the key of the third region  330 , as shown in  FIG. 3 . In this way, the user can intuitionally recognize the directions corresponding to the keys according to the shapes of the regions  310 ,  320 , and  330  and the marks formed on the keys.  
      The regions in which the first key input unit  211  and the second key input unit  212  are arranged may have various shapes.  FIG. 4  and  FIG. 5  show modifications of the shapes of the regions.  
       FIG. 4  shows a hexahedron having a first lozenge-shaped region  410 , a second region  420  formed adjacent to the first region  410 , and a third region  430  formed adjacent to the first region  410 . Among the regions  410 ,  420 , and  430 , an up key  411 , a down key  413 , a left key  412 , and a right key  414  are arranged in the first region  410  so as to correspond to the control directions of the keys, and a key  421  corresponding to the negative direction of the z-axis and a key  431  corresponding to the positive direction of the z-axis are arranged in the second region  420  and the third region  430 , respectively.  
      In this case, the keys  411 ,  412 ,  413 , and  414  may be arranged in the first region  410  have the same height such that the user can intuitionally recognize that the keys are used for directional movement in the x-y plane when the user touches the first region  410 .  
      On the other hand, the heights of the keys  421  and  431  arranged in the second region  420  and the third region  430  may become smaller, as the keys become more distant from the keys arranged in the first region  410 , that is, the keys  411 ,  412 ,  413  and  414  of the first key input unit  211 , such that the user can intuitionally recognize that the keys  421  and  431  arranged in the second and third regions  420  and  430  are used for movement in the z-axis direction, when touching the second region  420  and the third region  430 . That is, the keys arranged in the second region  420  and the third region  430  may be formed as in the cross section shown in  FIG. 4 .  
      According to an exemplary embodiment, marks are formed in the keys  421  and  431  respectively arranged in the second region  420  and the third region  430  such that the user can recognize the functions of the keys. For example, an arrow  422  representing the negative direction of the z-axis is marked in the second region  420 , and an arrow  432  representing the positive direction of the z-axis is marked in the third region  430 . In this way, the user can intuitionally recognize the directions corresponding to the keys according to the shapes of the regions  410 ,  420 , and  430  and the marks formed on the keys.  
       FIG. 5  shows a cylinder having a first circular region  510 , a second region  520  formed adjacent to the first region  510 , and a third region  530  formed adjacent to the first region  510 . Among the regions  510 ,  520 , and  530 , an up key  511 , a down key  513 , a left key  512 , and a right key  514  are arranged in the first region  510  so as to correspond to the control directions of the keys, and keys  521  and  531  corresponding to the negative and positive directions of the z-axis are arranged in the second region  520  and the third region  530 , respectively.  
      In this case, similar to the above-described exemplary embodiments, the keys  511 ,  512 ,  513 , and  514  arranged in the first region  510  may have the same height such that the user can intuitionally recognize that the keys are used for directional movement in the x-y plane when the user touches the keys  511 ,  512 ,  513 , and  514  of the first region  510 .  
      On the other hand, the heights of the keys  521  and  531  arranged in the second region  520  and the third region  530  become smaller, as the keys become more distant from the keys arranged in the first region  510 , that is, the keys  511 ,  512 ,  513  and  514  of the first key input unit  211 , such that the user can intuitionally recognize that the keys  521  and  531  respectively arranged in the second and third regions  520  and  530  are used for movement in the z-axis direction, when touching the keys  521  and  531  of the second region  520  and the third region  530 .  
      According to an exemplary embodiment, marks are formed in the keys  521  and  531  respectively arranged in the second region  520  and the third region  530  such that the user can recognize the functions of the keys. For example, an arrow  522  representing the negative direction of the z-axis is marked in the second region  520 , and an arrow  532  representing the positive direction of the z-axis is marked in the third region  530 . In this way, the user can intuitionally recognize the directions corresponding to the keys according to the shapes of the regions  510 ,  520 , and  530  and the marks formed on the keys.  
       FIG. 6  is a diagram illustrating an example of the arrangement of a first key input unit  211  and a second key input unit  212  according to another exemplary embodiment of the invention and a cross-sectional view taken along the line VI-VI′.  
      As shown in  FIG. 6 , an up key  611 , a down key  613 , a left key  612 , and a right key of the first key input unit  211  may be disposed in a cross shape in a region  610  with a run key  615  at the center thereof. The run key  615  may be optionally provided. A key  621  corresponding to the negative direction of the z-axis may be arranged between the up key  611  and the right key  614  on a diagonal line passing through the center of the run key  615 , and a key  631  corresponding to the positive direction of the z-axis may be arranged between the left key  612  and the down key  613  on the diagonal line passing through the center of the run key  615 .  
      In this case, since the up key  611 , the down key  613 , the left key  612 , and the right key  614  are used for directional movement in the x-y plane, the keys may be formed to have the same height. In contrast, as shown in the cross section in  FIG. 6 , the height of the key  621  corresponding to the negative direction of the z-axis may become smaller, as it becomes more distant from the run key  615 , such that the user can intuitionally recognize that the key  621  is used for movement in the negative direction of the z-axis, when touching the key  621 . In addition, as shown in  FIG. 6B , the height of the key  631  corresponding to the positive direction of the z-axis may become larger, as it becomes more distant from the run key  615 , such that the user can intuitionally recognize that the key  631  is used for movement in the positive direction of the z-axis, when touching the key  631 .  
      The input unit  210  may further include a power key (not shown) for supplying power to the navigation apparatus  200  and number keys (not shown) for inputting numbers, in addition to the first key input unit  211  and the second key input unit  212 . When the user pushes the keys of the input unit  210 , the keys generate key signals. The generated key signals are transmitted to the control unit  230 . The input unit  210  may be integrated into the navigation apparatus  200  in a hardware manner, or it may be formed of a module separated from the navigation apparatus  200 . When the input unit  210  is formed of a module separated from the navigation apparatus  200 , the input unit  210  can transmit the input value input by the user to the navigation apparatus  200  by means of wire or wireless communication.  
      Next, a navigation process of the navigation apparatus according to an exemplary embodiment of the invention will be described below with reference to  FIGS. 7A  to  8 .  FIGS. 7A  to  7 D are diagrams illustrating an example of a three-dimensional graphic user interface of the navigation apparatus  200  according to the exemplary embodiment of the invention.  FIG. 8  is a flowchart illustrating a navigation process performed by the navigation apparatus according to an exemplary embodiment of the invention.  
      The three-dimensional graphic user interface shown in  FIGS. 7A  to  7 D includes first to third polyhedral objects  710 ,  720 , and  730  arranged on the x-axis, fourth and fifth polyhedral objects  740  and  750  that are arranged on the y-axis with the second polyhedral object  720  at the center thereof, and sixth and seventh polyhedral objects  760  and  770  that are arranged on the z-axis with the second polyhedral object  720  at the center thereof.  
      When an input value is input through the input unit  210 , with the three-dimensional graphic user interface displayed by the display unit  210 , the control unit  230  generates an instruction code corresponding to the input value and transmits the generated instruction code to the object control unit  250 . For example, when the right key of the input unit  210  is pushed, the control unit  230  generates an instruction code corresponding to a key signal of the right key and transmits the generated instruction code to the object control unit  250  (S 800 ).  
      The object control unit  250  determines whether the instruction code transmitted from the control unit  230  is an instruction code for the first key input unit  211  and the second key input unit  212  (S 810 ).  
      When it is determined that the transmitted instruction code is not the instruction code for the first key input unit  211  and the second key input unit  212  (S 810 ; No), for example, when the transmitted instruction code is an instruction code for the run key (not shown) or a cancel key (not shown), the object control unit  250  executes or cancels the instruction associated with the polyhedral object currently selected. More specifically, as shown in  FIG. 7A , when the run key  315 ,  415 ,  515 , or  615  is pushed with the second polyhedral object  720  corresponding to “Schedule” being selected, the object control unit  250  displays a calendar as detailed information related to “Schedule”, as shown in  FIG. 7B .  
      On the other hand, when it is determined that the transmitted instruction code is the instruction code for the first key input unit  211  and the second key input unit  212  (S 810 ; Yes), the object control unit  250  performs directional movement in the three-dimensional graphic user interface, according to the kind of instruction code transmitted from the control unit  230  (S 830 ).  
      For example, when the instruction code transmitted from the control unit  230  is the instruction code for the first key input unit  211 , the object control unit  250  performs directional movement in the x-y plane according to the kind of input instruction code (S 850 ). More specifically, when the right key  314 ,  414 ,  514 , or  614  is pushed with the second polyhedral object  720  being selected as shown in  FIG. 7A , the object control unit  250  forms an outline in the periphery of the third polyhedral object  730  to emphasize the third polyhedral object  730 , as shown in  FIG. 7C .  
      For example, when the instruction code transmitted from the control unit  230  is the instruction code for the second key input unit  212 , the object control unit  250  performs directional movement in the z-axis according to the kind of input instruction code (S 840 ). More specifically, when the key  322 ,  422 ,  522 , or  622  corresponding to the negative direction of the z-axis is pushed with the second polyhedral object  720  being selected as shown in FIG.  7 A, the object control unit  250  forms an outline in the periphery of the seventh polyhedral object  770  to emphasize the seventh polyhedral object  770 , as shown in  FIG. 7D . In this case, the object control unit  250  may move a view point toward the seventh polyhedral object  770  such that the seventh polyhedral object  770  appears to zoom in along the z-axis direction.  
      Steps S 810  to S 850  are performed by the object control unit  250 , and the result processed by the object control unit  250  is displayed by the display unit  260  (S 860 ).  
      While the navigation apparatus  200  and method for the three-dimensional graphic user interface according to the exemplary embodiments of the present invention have been described above with reference to the accompanying drawings, it will be understood by those skilled in the art that various modifications and changes of the invention can be made without departing from the scope and spirit of the invention. Therefore, it should be understood that the above-described exemplary embodiments are not restrictive, but illustrative in all aspects.  
      As described above, the navigation apparatus for a three-dimensional graphic user interface according to the present invention can obtain the following effects.  
      First, it is possible to easily perform directional movement in the x-y plane and in the z-axis direction by providing input units for the x-axis, y-axis, and z-axis directions.  
      Second, a user can intuitionally recognize the functions of keys according to the shapes of regions in which keys for directional movement in the x-y plane and keys for directional movement in the z-axis are arranged.  
      Third, a user can recognize the functions of keys by means of the sense of touch with the keys by making the height of the key for directional movement in the z-axis non-uniform.  
      Fourth, it is possible to prevent the confusion of use occurring when the user uses a two-dimensional input unit to navigate a three-dimensional graphic user interface.  
      While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.