Patent Publication Number: US-7593009-B2

Title: Apparatus and method for reconstructing three-dimensional graphics data

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2004-0027154, filed on Apr. 20, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for rendering 3D (three-dimensional) graphics data and more particularly to an apparatus and method for reconstructing 3D graphics data. 
     2. Description of the Related Art 
     A VRML (Virtual Reality Modeling Language), MPEG (Moving Picture Expert Group) standards, and a file format defined by a general commercial program (e.g., 3D Studio Max, Maya, etc.) are used by an apparatus for rendering 3D graphics data on a screen. 3D data includes: geometric information (e.g., information about positions of 3D points constituting an object and connection information thereof) of an object positioned in 3D space; material information of an object (e.g., information about texture, transparency of an object, color of an object, and shininess of an object&#39;s surface); and information about change of such information depending on position, characteristics of a light source, and time. Such 3D graphics data is expressed with a structure intuitively or logically understandable so that a user may easily generate and modify the graphics data. An object in which 3D graphics data is expressed with a structure intuitively understandable in this manner is called a scene graph. 
       FIG. 1  is a diagram illustrating an example of a node structure of a scene graph. As shown in  FIG. 1 , the scene graph stores 3D graphic data in a plurality of nodes (group nodes and shape nodes). The group nodes have information about sub-nodes and the shape nodes are leaf nodes and store geometric information and/or material information of an object. In particular, the scene graph includes: nodes that include geometric information and/or material information of an object and connection information that forms a hierarchy by connecting the nodes. Also, some information including position information and rotational information of the node influences position of the sub-nodes. The strong point of such a structure is that its subordinate relationship is easy for a person to understand intuitively according to the relative positions of the nodes. 
       FIG. 2  is a scene graph of a 3D human body structure. As shown in  FIG. 2 , suppose that a body of a “person” is expressed in the 3D space. With an abstract node “person” used as a starting node, a “person” is roughly divided into “chest” and “stomach” parts, and the “chest” and the “stomach” are sub-nodes of the node “person”. Also, sub-nodes of the “chest” include a “head,” a “right arm” and a “left arm,” and sub-nodes of the “stomach” include a “left leg” and a “right leg”. Information in a high ranking node has a direct influence on a sub-node. Therefore, if position information of the node “person” is changed, such position change information directly influences each of the sub-nodes. Thus, to change the whole body information of a “person” generated in the 3D space, only the relevant information in the node “person” needs to be changed. Such a structure is very convenient and intuitive from the viewpoint of a user who generates and modifies 3D data, because, as described above, only information of the node “person”, the highest ranking node, needs to be modified when moving the entire body, not the position information of each part of the body. Also, when changing part of the body information, only the information of the relevant node needs to be changed, without changing information in the sub-nodes. 
     To read in such 3D graphics data and output the same to a screen, an apparatus for analyzing the meaning of the read 3D graphics data and performing data conversion, is required. Generally, such an apparatus is called a 3D graphics rendering engine. The 3D graphics rendering engine includes a parser and a renderer. 
     The parser reads in and interprets 3D graphics data. Namely, the parser identifies whether the read data is geometric information of an object, material information of an object, or information about a subordinate relationship between objects originated from the scene graph structure, and interpreting and judging the information. 
     The renderer changes the scene graph parsed by the parser into a form appropriate for display on a screen of an output device. Since a screen is appropriate for displaying 2D information, the 3D scene graph cannot be directly used. A primary role of the renderer is to convert 3D graphics data into 2D graphics data by performing a coordinate transformation on an object expressed in 3D space. Therefore, output data from the renderer is converted into 2D graphics data. 
     However, a problem with such a conventional 3D graphics rendering engine lies in producing a 2D output image by performing a 2D data conversion process only on 3D graphics data without changing a 3D graphics data structure. The scene graph, which is a method for expressing a data structure of the 3D graphic data, is an easy structure that can be easily understood and modified intuitively by a user as described above, but storage space is wasted, generation of an output image is delayed, and image quality of the output image is deteriorated. As shown in  FIG. 2 , there exist nodes that include the same kinds of material information and such nodes are arranged in a discontinuous and irregular order. The renderer converts 3D graphics data of each node into 2D data without changing the scene graph&#39;s structure. 
       FIG. 3  is a diagram illustrating an order of data conversion of the scene graph shown in  FIG. 2 . Referring to  FIG. 3 , even if the same kind of material information appears repeatedly, the renderer cannot be aware of such information during the rendering process. Therefore, the renderer repeatedly stores all material information appearing according to a predetermined order in a data storage space on a terminal. Therefore, when using the conventional 3D graphics rendering engine, waste of storage space occurs. 
     Also, when material information changes between two neighboring nodes during the rendering process, the renderer throws away the original material information and reads the new material information into the storage space of the terminal. Generally, since the process of reading and/or writing data from and to the storage space requires more time compared to other processes such as mathematical computation, such information change causes a large delay in the whole process of converting 3D information into 2D information. Since the conventional 3D graphics rendering engine always reads material information due to a discontinuous arrangement of the same material information, the generation of an output image is delayed. 
     Also, information representing transparency of an object may be included in the information held by the 3D graphics data. When the nodes having this information are arranged in a discontinuous and irregular order, exact conversion of 3D information into 2D information cannot be guaranteed. When 3D objects having a transparent property are positioned in an overlapping manner, conversion of 3D information into 2D information should be performed by reflecting characteristics such as transparency and the distance of other 3D objects existing in the viewing frustum. However, since the conventional 3D graphics rendering engine does not reflect transparency and distance between 3D objects that belong to each node when determining a rendering order, deterioration in image quality of an output image occurs. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides an apparatus and method for reconstructing 3D graphic data capable of grouping nodes of a scene graph according to material information such as transparency information and texture information. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
     According to an aspect of the present invention, there is provided an apparatus for reconstructing 3D graphics data including: a parsing unit to parse 3D graphics data; an aligning unit to align nodes storing geometric information and material information that corresponds to the geometric information included in the 3D graphics data parsed by the parsing unit, and objects of a scene graph having hierarchy information regarding the nodes using predetermined detail information included in the material information as a reference; and a rendering unit to interpret the objects of the scene graph aligned by the aligning unit to convert the 3D graphics data into 2D graphics data. 
     According to another aspect of the present invention, there is provided a method of reconstructing 3D graphics data including: parsing 3D graphics data; aligning nodes storing geometric information and material information that corresponds to the geometric information included in the 3D graphics data, and objects of a scene graph having hierarchy information regarding the nodes using predetermined detail information included in the material information as a reference; and interpreting the aligned objects of the scene graph to convert the 3D graphics data into a 2D graphics data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a diagram illustrating an example of a node structure of a scene graph; 
         FIG. 2  is a scene graph illustrating a 3D body structure; 
         FIG. 3  is a diagram illustrating an order of data conversion of the scene graph shown in  FIG. 2 , according to an embodiment of the present invention; 
         FIG. 4  is a block diagram of an apparatus for reconstructing 3D graphics data according to an embodiment of the present invention; 
         FIG. 5  is a block diagram of an aligning unit shown in  FIG. 4 , according to an embodiment of the present invention; 
         FIG. 6  is a block diagram of a first scene graph interpreting unit shown in  FIG. 5 , according to an embodiment of the present invention; 
         FIG. 7  is a block diagram of a detail information classifying unit shown in  FIG. 5 , according to an embodiment of the present invention; 
         FIG. 8  is a schematic representation of a storage structure of transparent geometric information stored in a transparent geometric storage unit shown in  FIG. 7 , according to an embodiment of the present invention; 
         FIG. 9  is a schematic representation of a storage structure of opaque geometric information stored in an opaque geometric storage unit shown in  FIG. 7 , according to an embodiment of the present invention; 
         FIG. 10  is a schematic representation of a scene graph, according to an embodiment of the present invention; 
         FIGS. 11A and 11B  are diagrams illustrating results after aligning the scene graph shown in  FIG. 10 , according to an embodiment of the present invention; 
         FIG. 12  is a block diagram of a rendering unit shown in  FIG. 4 , according to an embodiment of the present invention; 
         FIG. 13  is a flowchart illustrating a method of reconstructing 3D graphic data according to an embodiment of the present invention; 
         FIG. 14  is a flowchart illustrating an alignment operation shown in  FIG. 13 , according to an embodiment of the present invention; 
         FIG. 15  is a flowchart illustrating an interpretation operation shown in  FIG. 14 , according to an embodiment of the present invention; 
         FIG. 16  is a flowchart illustrating a classification and storage operation shown in  FIG. 14 , according to an embodiment of the present invention; and 
         FIG. 17  is a flowchart illustrating a conversion operation shown in  FIG. 13 , according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
     The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these 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. 
       FIG. 4  is a block diagram of an apparatus for reconstructing 3D graphics data according to an embodiment of the present invention. The apparatus for reconstructing 3D graphics data includes a parsing unit  100 , an aligning unit  120 , and a rendering unit  140 . 
     The parsing unit  100  reads in and parses 3D graphics data such as VRML (Virtual Reality Modeling Language) data, or MPEG (Moving Picture Expert Group) data. The parsing unit  100  parses the scene graph of the 3D graphics data which is input through an input terminal IN 1 , and outputs information regarding the parsed scene graphs, to the aligning unit  120 . The scene graph has nodes that include geographic information and material information that corresponds to the geographic information, and also has hierarchy information of the nodes. Assume that detail information regarding geometric information and material information of the scene graphs, is an object of the scene graph. The geometric information is said to be 3D information representing the appearance of an object. The material information includes detail information. The detail information represents texture, transparency of an object, color of an object and shininess of an object&#39;s surface. Since the specific functions of the parsing unit  100  are similar to the conventional art, a description thereof will be omitted. 
     The aligning unit  120  aligns objects of the scene graph parsed by the parsing unit  100  using as a reference predetermined detail information included in the material information, and outputs the objects of the aligned scene graph to the rendering unit  140 . In one embodiment, aligning is performed on the transparency information and the texture information included in the predetermined detail information. The transparency information is divided into transparent geometric information and opaque geometric information depending on transparency. Transparent geometric information and opaque geometric information are separated and individually stored. The opaque geometric information is aligned according to texture information and the transparent geometric information is aligned in consideration of a distance between a camera and a position of the transparent geometric information. 
       FIG. 5  is a block diagram of the aligning unit  120  shown in  FIG. 4 , according to an embodiment of the present invention. The aligning unit includes a first scene graph interpreting unit  200 , a detail information classifying unit  220 , and a classification completion determination unit  260 . 
     The first scene graph interpreting unit  200  receives objects of the scene graph parsed by the parsing unit  100  via an input terminal IN 2 , and interprets the objects of the input scene graph and outputs the same to the detail information classifying unit  220 . 
       FIG. 6  is a block diagram of the first scene graph interpreting unit  200  shown in  FIG. 5 , according to an embodiment of the present invention. The first scene graph interpreting unit  200  includes a shape node determination unit  300  and a sub-node detecting unit  320 . 
     When the scene graph is received via an input terminal IN 3 , the shape node determination unit  300  determines whether a node is a shape node of the scene graph, and outputs the determination results to the sub-node detecting unit  320  or to the detail information classifying unit  220  via an output terminal OUT 3 . A shape node is a node storing the geometric information and material information that corresponds to the geometric information. Since the shape node is a leaf node, the shape node does not have sub-nodes. If the node inspected by the shape node determination unit  300  is not a shape node, the inspected node is a group node having sub-nodes. If the inspected node is a shape node, the shape node determination unit  300  outputs the determination results to the detail information classifying unit  220  via the output terminal OUT 3 . However, if the inspected node is not a shape node, the shape node determination unit  300  outputs the determination results to the sub-node detecting unit  320 . 
     The sub-node detecting unit  320  detects sub-nodes connected to a sub-hierarchy of the inspected node. If the determination results indicate that the inspected node has sub-nodes, the sub-node detecting unit  320  detects the sub-nodes in the sub-hierarchy of the inspected node, and outputs the detected results to the shape node determination unit  300 . 
     When the result of detection is received from the sub-node detecting unit  320 , the shape node determination unit  300  determines whether the detected sub-nodes are shape nodes. 
     When objects of the interpreted scene graph are received from the first scene graph interpreting unit  200 , the detail information classifying unit  220  classifies and stores the interpreted objects using predetermined detail information as a reference, and outputs the stored results to the classification completion determination unit  260 . 
       FIG. 7  is a block diagram of the detail information classifying unit  220  shown in  FIG. 5 , according to an embodiment of the present invention. The detail information classifying unit  220  includes a matrix storage unit  400 , a detail information access unit  420 , a transparent geometric storage unit  440 , and an opaque geometric storage unit  460 . 
     The matrix storage unit  400  determines which hierarchy of the scene graph the read shape node belongs to, computes a GTM (Global Transformation Matrix) capable of performing conversion from local coordinates of the relevant hierarchy to global coordinates, stores the results in the read shape node, and outputs the read shape node to the detail information access unit  420 . 
     The detail information access unit  420  reads predetermined detail information of the material information of the shape node. The detail information access unit  420  reads predetermined detail information of the material information of the interpreted shape node and outputs the same to the transparent geometric storage unit  440  or the opaque geometric storage unit  460  according to the predetermined detail information. 
     In particular, the detail information access unit  420  reads texture information and/or transparency information of the predetermined detail information of the material information of the shape node. If the transparency information is transparent geometric information representing something transparent, the detail information access unit  420  outputs the read shape node to the transparent geometric storage unit  440 ; and if the transparency information is the opaque geometric information representing something opaque, the detail information access unit  420  outputs the read shape node to the opaque geometric storage unit  460 . 
     The transparent geometric storage unit  440  uses a one-dimensional array storage structure to store the read shape node. After a distance between the read shape node and a camera viewing the transparent geometric information is computed, the shape nodes are stored in the array, in which shape nodes which are distant from the camera are stored first, and shape nodes which are close to the camera are stored later. Such a storing order is intended to prevent image quality deterioration due to corruption of the transparent geometric information. 
       FIG. 8  is a schematic representation of a storage structure of transparent geometric information stored in the transparent geometric storage unit  440  shown in  FIG. 7 , according to an embodiment of the present invention. As shown in  FIG. 8 , transparent geometric information of the shape node farthest from the camera is stored in a transparent object  1 . Transparent geometric information of a shape node closer to the camera than the shape stored in the transparent object  1 , is stored in a transparent object  2 . Shape nodes successively closer to the camera are stored in a transparent object  3  and a transparent object  4 , respectively. 
     The opaque geometric storage unit  460  has a ring structure for storing texture information included in the detail information. The ring structure, in which first data and last data are stored in adjacent storage units, denotes a storage structure of a linked list. 
     The opaque geometric storage unit  460  determines whether texture information included in the detail information of the read shape node is already included in the ring. If the texture information is not included in the ring, the texture information is added to the ring and the opaque geometric information of the shape node is stored in a sub-ring of the texture information. If the texture information is already included in the ring, the texture information is not added to the ring, and the opaque geometric information of the shape node is stored in a sub-ring of the texture information which is already stored in the ring. 
       FIG. 9  is a schematic representation of a storage structure of opaque geometric information stored in the opaque geometric storage unit  460  shown in  FIG. 7 , according to an embodiment of the present invention.  FIG. 9  exemplarily shows the texture information included in the detail information. As shown in  FIG. 9 , the opaque geometric storage unit  460  uses a texture ring to store the texture information (texture  1 ,  2 ,  3 ,  4 , and  5 ). In the texture ring, five pieces of texture information (texture  1 ,  2 ,  3 ,  4 , and  5 ) representing different textures are stored. The texture ring has sub-rings. In the sub-rings, opaque geometric information (opaque geometric  1 ,  2 ,  3 ,  4 ,  5 , and  6 ) including the texture of the texture information ( 1 ,  2 ,  3 ,  4 , and  5 ), is stored. 
       FIG. 10  illustrates how a scene graph is reconstructed according to an embodiment of the present invention, and  FIGS. 11A and 11B  are diagrams illustrating the results after aligning the objects of the scene graph shown in  FIG. 10 , according to an embodiment of the present invention. 
     The scene graph shown in  FIG. 10  is reconstructed with use of the aligning unit  120 . The following description uses the array structure of the transparent geometric storage unit  440  exemplarily shown in  FIG. 8  and the ring structure of the opaque geometric storage unit  460  shown in  FIG. 9 . The shape nodes of the scene graph are first classified according to the transparency information. If the shape node includes the transparent geometric information which is the transparent information, the shape node is stored in the transparent geometric storage unit  440  as shown in  FIG. 11A . At this point, the order in which objects are stored in the transparent geometric storage unit  440  is determined according to the distance between the camera and the object. That is, an object that is farthest from the camera is aligned first. Therefore, referring to  FIG. 11A , second, fourth, and third geometric information is stored in the given order in consideration of the distance from the camera. 
     If the shape node includes opaque geometric information, the texture ring is constructed using the texture information included in the shape nodes and the geometric information that includes the texture information is stored in the sub-rings of the texture information, as shown in  FIG. 11B . Therefore, the first and fifth texture information constitute the texture ring, and the first and the fifth geometric information constitute the sub-rings. When the opaque geometric information includes the same texture information repeatedly, each piece of geometric information will be aligned in a sub-ring of a texture, which provides a structure in which large amounts of texture information can be processed in an efficient manner. 
     The classification completion determination unit  260  determines whether all the objects of the interpreted scene graph are classified, and outputs the determination results via the output terminal OUT 2 . At this point, if not all nodes of the interpreted scene graph are classified completely with the predetermined detail information used as a reference, the classification completion determination unit  260  outputs the determination results to the first scene graph interpreting unit  200 . The first scene graph interpreting unit  200  reinterprets the scene graph in response to the determination results of the classification completion determination unit  260 . 
     As described above, the scene graph is aligned based on each piece of texture information by the aligning unit, and thus the same texture information need not be stored repeatedly. 
     The rendering unit  140  interprets the objects of the scene graphs aligned by the aligning unit  120  to convert 3D data into 2D graphics data and outputs the converted 2D graphics data via the output terminal OUT 1 . 
       FIG. 12  is a block diagram of the rendering unit  140  shown in  FIG. 4 , according to an embodiment of the present invention. The rendering unit  140  includes an aligned scene graph interpreting unit  500  and a converting unit  520 . 
     The aligned scene graph interpreting unit  500  interprets predetermined detail information received via an input terminal IN 5  and the transparent and opaque geometric information that corresponds to the predetermined detail information, and outputs the interpreted results to the converting unit  520 . 
     The aligned scene graph interpreting unit  500  receives the texture information and the opaque geometric information stored in the sub-ring of the received texture information from the aligning unit  120 , and interprets the received texture information and the opaque geometric information. Also, the aligned scene graph interpreting unit  500  receives the transparent geometric information from the aligning unit  120  and interprets the received transparent geometric information. 
     The converting unit  520  converts the predetermined detail information, the transparent geometric information, and the opaque geometric information into 2D graphics data, and outputs the converted results via an output terminal OUT 5 . In particular, the converting unit  520  converts the 3D graphics data into the 2D graphics data starting with the transparent geometric information farthest from the camera and finished with the transparent geometric information closest to the camera, with respect to the interpreted transparent geometric information. 
     The rendering unit  140  interprets and converts the opaque geometric information first, and then interprets and converts the transparent geometric information. If rendering is performed on the aligned transparent object after rendering is performed on the aligned opaque object, image quality deterioration that may be generated due to the transparent object can be prevented. 
     A method for reconstructing the 3D graphics data according to an embodiment of the present invention will now be described with reference to the accompanying drawings. 
       FIG. 13  is a flowchart illustrating a method of reconstructing 3D graphics data according to an embodiment of the present invention. The method includes aligning objects of a scene graph of 3D graphics data using predetermined detail information as a reference and converting the 3D graphics data into 2D graphics data using the aligned scene graph. 
     First, the 3D graphics data is parsed (operation  1000 ). The scene graph among the 3D graphics data is also parsed. The scene graph includes the nodes that include geometric information and material information that corresponds to each piece of the geometric information. The scene graph also includes hierarchy information for the nodes. 
     Next, the objects of the scene graph of the 3D graphics data are aligned using the predetermined detail information of the material information as a reference (operation  1002 ). At this point, the aligned predetermined detail information is the transparency information and the texture information. 
       FIG. 14  is a flowchart illustrating the alignment operation  1002  shown in  FIG. 13 , according to an embodiment of the present invention. The operation  1002  includes: classifying the objects of the scene graph using the predetermined detail information as a reference, and determining whether such objects are all classified. 
     First, the objects of the scene graph are interpreted (operation  1100 ). 
       FIG. 15  is a flowchart illustrating the interpretation operation  1100  shown in  FIG. 14 , according to an embodiment of the present invention. The operation  1100  includes operations  1200  and  1202  of detecting sub-nodes of each of the nodes depending on whether the inspected node is a shape node or not. 
     First, it is determined whether one of the nodes is a shape node having the geometric and material information (operation  1200 ). 
     If the inspected node is not a shape node, the sub-nodes connected to the inspected node are detected and the operation  1200  (operation  1202 ) is performed. 
     However, if the inspected node is a shape node, the operation  1102  is performed. 
     After the operation  1100 , the objects of the interpreted scene graph are classified and stored using the predetermined detail information as a reference (operation  1102 ). 
       FIG. 16  is a flowchart illustrating the classification and storage operation  1102  shown in  FIG. 14 , according to an embodiment of the present invention. The operation  1102  includes: reading the predetermined detail information of the material information and storing the transparent and opaque geometric information. 
     First, a hierarchical position of the shape node is determined and a GTM is computed (operation  1300 ). 
     Then, the predetermined detail information of the material information stored in the shape node is read (operation  1302 ). 
     Subsequently, the transparent and opaque geometric information included in the material information of the shape node are stored (operation  1304 ). At this point, if the material information is opaque geometric information, the opaque geometric information is stored in the sub-ring structure of the texture information; and if the material information is transparent geometric information, the transparent geometric information is stored in the array structure. That is, depending on the opaque geometric information included in the material information stored in the shape node, the material information is divided into transparent object lists and opaque object lists, and the transparent object lists are aligned according to a distance between the transparent object and a camera viewing the transparent object. One ring is constructed by the textures used for the opaque object list, and a sub-ring is constructed for each object that includes the same texture information and stored. 
     Then, it is determined whether the objects of the scene graph are all classified (operation  1104 ). 
     If the objects of the scene graph are all classified, the operation  1004  is performed. However, if the objects of the scene graph are not all classified, the operations  1100  through  1104  are performed. 
     Next, the aligned scene graph is interpreted and the 3D graphics data is converted into the 2D graphics data (operation  1004 ). At this point, after the opaque geometric information included in the material information is interpreted and converted, the transparent geometric information is interpreted and converted. 
       FIG. 17  is a flowchart illustrating the conversion operation  1004  shown in  FIG. 13 , according to an embodiment of the present invention. 
     First, the predetermined detail information, and the transparent and opaque geometric information that correspond to the predetermined detail information are interpreted (operation  1400 ). 
     Then, the predetermined detail information, the transparent geometric information and the opaque geometric information are converted into the 2D graphics data (operation  1402 ). At this point, the 3D graphics data is converted into the 2D graphics data based on the order in which the transparent geometric information is aligned in operation  1304 . 
     Unlike conventional methods, in the present invention, 3D graphics data is classified according to its characteristics and the 3D graphics data is reconstructed according to the characteristics, whereby a fast and a more precise conversion of the 3D graphics data into a 2D graphics data is guaranteed and efficient management of the 3D graphics data is enhanced. Such characteristics of the present invention can be applied to a PC (personal computer) used in a fixed place, a mobile device such as a PDA (Personal Digital Assistant) or a cellular phone. 
     As described above, an apparatus and method for reconstructing 3D graphics data according to the present invention can omit operations of repeatedly storing the same texture information by using an aligning unit to classify each node of a scene graph into groups according to texture information. 
     Also, according to the present invention, since an operation of converting the 3D graphics data into the 2D data, can be performed for each group of the texture information, time loss in the data conversion due to change of the texture information during the conversion process can be minimized. 
     Also, the present invention classifies the geometric information by using the transparent information to sequentially perform data conversion according to the distance, from a viewing point, thereby converting the 3D graphics data into the 2D data in a more precise manner. 
     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.