KR102181812B1 - System and method for compression and decompression of 3d mesh model - Google Patents

Abstract

Embodiments of the present invention include a first input unit for receiving geometric information and connection information for a 3D mesh model; The geometric information includes coordinates of vertices, and the connection information includes a connection relationship of vertices constituting a plane, and a geometric information compression unit compressing the geometric information; A connection information remapping unit for updating the connection information; And it provides a 3D mesh model compression system comprising a connection information compression unit for compressing the updated connection information.
Accordingly, in the embodiments of the present invention, only the geometric information is first compressed by a method with a high compression rate, and then the connection information is updated to correspond to the compressed geometric information, and only the updated connection information can be compressed again by a method with a high compression rate. It is possible and updates the connection information of the original 3D mesh model, so there is no significant difference from the original even after the connection information is updated.

Description

3D mesh model compression and decompression system and method{SYSTEM AND METHOD FOR COMPRESSION AND DECOMPRESSION OF 3D MESH MODEL}

The present invention relates to a system and method for compressing and decompressing a 3D mesh model, and more particularly, to efficiently compress and decompress a 3D mesh model.

The 3D model can be divided into a mesh model and a point cloud.

The three-dimensional mesh model refers to a set of vertices and surfaces that define the shape of a polyhedral object, and the set of vertices is called geometry information, and the set of surfaces is called connectivity information. Is called. The face or surface of the 3D mesh model is mainly composed of triangles, and the three points of the triangle correspond to the vertices of the mesh.

On the other hand, a 3D point cloud refers to a model composed of a set of only vertices with only geometric information.

Regarding the 3D mesh model compression, the problems of the prior art related to the 3D mesh model and the 3D point cloud compression are examined.

3 bits/vertex), 기하정보 데이터량은 압축 후에도 여전히 높은 수준 (

9 bits/vertex)에 머무르게 된다. 따라서, 3차원 메쉬모델의 압축률을 향상시키기 위해서는 후술할 3차원 포인트 클라우드 압축과 같이 압축률이 높은 기하정보 압축을 연결정보 압축과 함께 수행해야 한다.The compression of the 3D mesh model is a method of compressing the geometric information first, then compressing the connection information based on the restored geometric information (Geometry-driven) and the method of compressing the connection information first, and then compressing the geometric information ( Connectivity-driven). Since the connection information data amount of the general 3D mesh model occupies more than twice the geometric information, the method of compressing the connection information first is mainly used, and representatively, there are the SC3DMC and Edgebreaker methods, which are standard technologies of MPEG. The method of pre-compressing the connection information can successfully compress the connection information, but (

3 bits/vertex), the amount of geometric data is still high even after compression (

9 bits/vertex). Therefore, in order to improve the compression rate of the 3D mesh model, it is necessary to compress geometric information with a high compression rate, such as 3D point cloud compression to be described later, together with compression of connection information.

2.5 bits/vertex)이 제안되었지만, 이와 같은 압축 기술들은 연결정보와 독립적으로 기하정보에 대한 압축을 수행하므로 연결정보를 가진 3차원 메쉬모델에 바로 적용할 경우 연결정보와 압축된 기하정보가 대응되지 않는 문제가 발생할 수 있다. 따라서, 3차원 포인트 클라우드 압축(기하정보 압축)과 연결정보 압축을 함께 수행하기 위해서는 연결정보를 압축하기 전에 연결정보를 압축된 기하정보에 대응(맵핑)시켜야 한다.Since the 3D point cloud is generated in the acquisition step of 3D model information (eg, 3D scanning), it has a large amount of geometric information through an elaborate acquisition step. Therefore, in order to efficiently compress large-capacity geometric information of the 3D point cloud, various compression techniques (

2.5 bits/vertex) was proposed, but since these compression techniques perform compression on geometric information independently of the connection information, when applied directly to a 3D mesh model with connection information, the connection information and the compressed geometric information cannot be matched. Can cause problems. Therefore, in order to perform 3D point cloud compression (geometric information compression) and connection information compression together, the connection information must be mapped (mapped) to the compressed geometric information before the connection information is compressed.

As one method for matching connection information to compressed geometric information, progressive mesh compression creates new connection information based on the compressed geometric information. It looks at the related art.

Korean Patent Registration No. 10-1590185 relates to a method of compressing and restoring 3D mesh information. The compression method comprises a process of constructing an octree and encoding geometric information of points accordingly, determining a triangular mesh, and The process of determining one side of the current gate as the current gate, the process of selecting a candidate group to allocate an index for points not visited by the current gate, the process of allocating the indexes to the selected points in the order of the shortest distance from the current gate Disclosed is a method of compressing and restoring 3D mesh information including a process of encoding an index assigned to a point in front of the current gate and returning to the process of determining the current gate if there is an unvisited triangle mesh. .

However, in the prior art, since the connection information needs to be newly created to correspond to the compressed geometric information, it takes a lot of time, and since the connection information is newly created without using the existing connection information, a 3D mesh model based on the newly created connection information The difference from the original 3D mesh model based on the existing connection information may be large.

In order to solve the above-described problem, embodiments of the present invention provide a first input unit for receiving geometric information and connection information for a 3D mesh model, the geometric information including coordinates of a vertex, and the connection information Consisting of including the connection relationship between the constituent vertices, and including a geometric information compression unit for compressing the geometric information, a connection information remapping unit for updating the connection information, and a connection information compression unit for compressing the updated connection information Its purpose is to provide a 3D mesh model compression system.

In addition, an object of the present invention is to provide a 3D mesh model compression system, characterized in that connection information associated with a vertex changed to another vertex, merged with another vertex, or disappeared by quantization is updated.

In addition, embodiments of the present invention provide that when a vertex is changed to another vertex in the process of compressing geometric information, the corresponding vertex is updated from the connection information, and the overlapping or non-existent side is deleted from the connection information to update the connection information. Its purpose is to provide a characteristic 3D mesh model compression system.

In addition, an object of the present invention is to provide a 3D mesh model compression system, characterized in that different indexes are set at vertices of geometric information and connection information is managed using the index.

In addition, an object of the present invention is to provide a 3D mesh model compression system, characterized in that the connection information is compressed using an index or a difference value of the index.

Further, an object of the present invention is to provide a 3D mesh model compression system, characterized in that whether or not a connection information remapping unit and a connection information compression unit are performed is determined according to a compression mode.

In addition, embodiments of the present invention include a second input unit for receiving compressed geometric information and compressed connection information for a 3D mesh model; The compressed geometric information includes the coordinates of the compressed vertex, and the compressed connection information includes information obtained by compressing a set of faces consisting of the index of the vertex, and the coordinates of the vertex from the compressed geometric information A geometric information decompression unit for restoring; And a connection information decompression unit for restoring connection information consisting of the coordinates of the vertex from the compressed connection information based on the coordinates of the restored vertex. An object thereof is to provide a 3D mesh model decompression system. .

An embodiment of the present invention for achieving the above object includes: a first input unit for receiving geometric information and connection information for a 3D mesh model; The geometric information includes coordinates of vertices, and the connection information includes a connection relationship of vertices constituting a plane, and a geometric information compression unit compressing the geometric information; A connection information remapping unit for updating the connection information; And it provides a 3D mesh model compression system comprising a connection information compression unit for compressing the updated connection information.

In one embodiment, the geometric information compression unit includes a voxelizer or a geometric information conversion unit that quantizes a coordinate value of a vertex included in the geometric information, and the connection information remapping unit is changed to another vertex or a different vertex by the quantization. Connection information associated with a vertex merged with or destroyed can be updated.

In one embodiment, the connection information remapping unit updates the corresponding vertex from the connection information when a vertex is changed to another vertex in the process of compressing the geometric information, and deletes the overlapping or non-conforming surface from the connection information. Information can be updated.

In one embodiment, the connection information remapping unit sets different indexes at the vertices of the geometric information and manages the connection information using the index, and the connection information compression unit uses the index or the difference value of the index. The updated connection information can be compressed.

In one embodiment, the 3D mesh model compression system includes a first mode determining unit that determines a compression mode, and whether the connection information remapping unit and the connection information compression unit are performed may be determined according to the compression mode.

In addition, another embodiment of the present invention for achieving the above object is a second input unit for receiving the compressed geometric information and the compressed connection information for the 3D mesh model; The compressed geometric information includes the coordinates of the compressed vertex, and the compressed connection information includes information obtained by compressing a set of faces consisting of the index of the vertex, and the coordinates of the vertex from the compressed geometric information A geometric information decompression unit for restoring; And a connection information decompression unit for restoring connection information composed of the coordinates of the vertex from the compressed connection information based on the coordinates of the restored vertex.

In addition, another embodiment of the present invention for achieving the above object includes a first input step of receiving geometric information and connection information for a 3D mesh model; A geometric information compression step of compressing the geometric information, wherein the geometric information is composed of the coordinates of the vertices, and the connection information is composed of a connection relationship of the vertices constituting the surface; A connection information remapping step of updating the connection information; And it provides a 3D mesh model compression method comprising a connection information compression step of compressing the updated connection information.

In addition, another embodiment of the present invention for achieving the above object is a second input step of receiving compressed geometric information and compressed connection information for a 3D mesh model; The compressed geometric information includes the coordinates of the compressed vertex, and the compressed connection information includes information obtained by compressing a set of faces consisting of the index of the vertex, and the coordinates of the vertex from the compressed geometric information A geometric information decompression step of restoring a; And a connection information decompression step of restoring connection information composed of the coordinates of the vertex from the compressed connection information based on the coordinates of the restored vertex.

As described above, the embodiments of the present invention provide a first input unit for receiving geometric information and connection information for a 3D mesh model, the geometric information including the coordinates of the vertices, and the connection information of the vertices constituting the plane. A three-dimensional mesh comprising a connection relationship and comprising a geometric information compression unit for compressing the geometric information, a connection information remapping unit for updating the connection information, and a connection information compression unit for compressing the updated connection information By providing a model compression system, it is possible to compress only the geometric information in a high compression rate first, then update the connection information to correspond to the compressed geometric information, and then compress only the updated connection information again in a method with a high compression rate. And, since the connection information of the original 3D mesh model is updated, there is no significant difference from the original even after the connection information is updated.

In addition, embodiments of the present invention set different indexes at the vertices of geometric information, manage the connection information using the indexes of the vertices, and compress the updated connection information using the index or difference value of the index, You can update the data quickly and efficiently, perform fast compression, and improve the compression rate.

In addition, embodiments of the present invention determine whether to perform the connection information remapping unit and the connection information compression unit according to the compression mode, so that it can be used with optimal performance in not only 3D mesh model compression but also 3D point cloud compression.

It is not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art from the following description.

1 is a block diagram illustrating an exemplary 3D mesh model compression system according to an embodiment.
2 is a diagram illustrating an exemplary data flow in a 3D mesh model compression system according to an embodiment.
3 is a diagram illustrating an octree partitioning process according to an embodiment.
4 is a diagram illustrating a change in connection information according to a change in geometric information.
5 is a diagram illustrating another example of a change in connection information according to a change in geometric information.
6 and 7 are diagrams illustrating a process of updating connection information of a connection information remapping unit according to an embodiment.
8 is a diagram showing the Edgebreaker method.
9 is a diagram illustrating a data flow of a 3D mesh model compression system in a 3D point cloud compression mode according to an embodiment.
10 is a block diagram illustrating an exemplary system for decompressing a 3D mesh model according to an exemplary embodiment.
11 is a diagram illustrating an exemplary data flow in a 3D mesh model compression system according to an embodiment.
12 is a diagram illustrating a data flow of a 3D mesh model decompression system in a 3D point cloud decompression mode according to an exemplary embodiment.
13 is a flowchart illustrating a method of compressing a 3D mesh model according to an embodiment of the present invention.
14 is a flowchart illustrating a method of decompressing a 3D mesh model according to an embodiment of the present invention.

Since the description of the present invention is merely examples for structural or functional description, the scope of the present invention should not be construed as being limited by the embodiments described in the text. That is, since the present embodiments can be variously changed and have various forms, the scope of the present invention should be understood to include equivalents capable of realizing the technical idea. In addition, since the object or effect presented in the present invention does not mean that a specific embodiment should include all of them or only those effects, the scope of the present invention should not be understood as being limited thereto.

In addition, the accompanying drawings are provided to aid in the understanding of the present invention, and provide embodiments together with a detailed description. However, the technical features of the present invention are not limited to a specific drawing, and features disclosed in each drawing may be combined with each other to constitute a new embodiment.

The three-dimensional mesh model compression and decompression system disclosed in the following embodiments will be described in more detail with reference to each drawing.

1 is a block diagram illustrating an exemplary 3D mesh model compression system according to an embodiment.

2 is a diagram illustrating an exemplary data flow in a 3D mesh model compression system according to an embodiment.

Referring to FIG. 1, a 3D mesh model compression system 100 according to an embodiment includes a first input unit 110, a coordinate conversion unit 120, a geometric information compression unit 130, and a connection information remapping unit 140. ), connection information compression unit 150, color information compression unit 160, first mode determination unit 170, first output unit 180, first transmission and reception unit 185, first database 190 and It may be configured to include the first control unit 195.

Referring to FIG. 2, the 3D mesh model compression system 100 according to an embodiment includes information on the 3D mesh model received from the first input unit 110, (i) geometric information is a coordinate conversion unit 120 , The voxel conversion unit 132, the connection information re-mipping unit 140, the geometric information conversion unit 134, the geometric information encoding unit 136, and compressed through (ii) the connection information is a coordinate conversion unit 120, a voxel conversion unit ( 132), the connection information re-mipping unit 140, the geometric information conversion unit 134, the connection information re-mipping unit 140, the connection information conversion unit 152, and the connection information encoding unit 154 to be compressed and (iii) color The information is compressed through a coordinate conversion unit 120, a voxel conversion unit 132, a connection information re-mipping unit 140, a geometric information conversion unit 134, a color information conversion unit 162, and a color information encoding unit 164. .

In FIG. 2, the connection information re-mipping unit 140 appears immediately after the voxelization unit 132 and immediately after the geometric information conversion unit 134, and is quantized by the voxelization unit 132 and the geometric information conversion unit 134, respectively. This is because remapping of the connection information may be necessary when doing this. Therefore, if the geometric information conversion unit 134 does not perform quantization, unlike FIG. 2, the connection information re-mipping unit 140 immediately behind the geometric information conversion unit 134 may be omitted.

However, even if both the voxelization unit 132 and the geometric information conversion unit 134 perform quantization, unlike FIG. 2, it may be configured to appear only once immediately after the geometric information conversion unit 134. That is, the connection information re-mipping unit 140 may be configured to process two quantizations performed by the voxelization unit 132 and the geometric information conversion unit 134 at once.

Here, quantization will be described later in the voxelization unit 132 or the like.

In this way, connection information remapping between the geometric information compression unit 130 including the voxelization unit 132 or the geometric information conversion unit 134 and the connection information compression unit 150 including the connection information conversion unit 152 By arranging the unit 140, only the geometric information is first compressed (geometric information compression unit) in a method with a high compression rate, and then the connection information is updated (connection information remapping unit) to correspond to the compressed geometric information, and only the updated connection information is Since it can be compressed again (connection information compression unit) in a method with a high compression rate, efficient compression can be performed.

Hereinafter, each configuration will be described.

The first input unit 110 may receive geometric information, connection information, and color information for the 3D mesh model through the first transmission/reception unit 185 or from the first database 190.

Here, the 3D mesh model may include a mesh constituting the surface shape of the 3D model, which is a polyhedron, and color information of the mesh, and the mesh includes geometric information and faces corresponding to a set of vertices. It may be configured by including connectivity information corresponding to a set of connection relationships of the constituent vertices. Specifically, the geometric information may be configured including the coordinates of the vertices, and the connection information may be configured including the coordinates of the connected vertices to form a plane.

The coordinate conversion unit 120 may move the coordinates of all vertices included in the geometric information to a value greater than 0 in order to facilitate compression of the 3D model. In addition, the coordinate conversion unit 120 sets the moving value of the coordinate by 3 so that the vertex included in the geometric information can be returned to the original coordinate in the coordinate restoration unit 250 of the 3D mesh model decompression system 200 to be described later. It can be delivered to the dimensional mesh model decompression system 200.

The geometric information compression unit 130 may include a voxelization unit 132, a geometric information conversion unit 134, and a geometric information encoding unit 136, and may compress geometric information.

이하([0,

])인 정수 값을 가지도록 양자화를 수행할 수 있다. 이 때에, 3차원 메쉬모델의 기하정보에 포함된 정점의 개수가 감소할 수 있는데 정점의 개수가 감소하면 정점을 연결한 연결정보도 변경될 수 있다. 변경된 연결정보를 갱신하는 방법은 후술할 연결정보 재맵핑부(140)에서 살펴본다.In the voxel conversion unit 132, the coordinates of the vertices having a value greater than 0 by the coordinate conversion unit 120 are 0 or more,

Less than ([0,

Quantization can be performed to have an integer value of ]). At this time, the number of vertices included in the geometric information of the 3D mesh model may decrease. If the number of vertices decreases, the connection information connecting the vertices may also be changed. A method of updating the changed connection information will be described in the connection information remapping unit 140 to be described later.

The geometric information conversion unit 134 can compress the geometric information by efficiently expressing the geometric information quantized by the voxelization unit 132. The geometric information conversion unit 134 may use an octree decomposition method or a Kd-tree decomposition method in order to efficiently express the geometric information.

Here, octree decomposition is a method of repetitively dividing a three-dimensional space into eight (Octree decomposition) and expressing whether there are vertices in the divided space as 0 and 1. Through octree division, the coordinates of a vertex can be expressed theoretically with only about 2.5 bits per vertex.

Also, here, Kd-tree decomposition is a spatial division technique similar to octree division to express vertices in k-dimensional space.

3 is a diagram illustrating an octree partitioning process according to an embodiment.

Referring to FIG. 3, octree partitioning according to an embodiment is initially performed at the L0 level, and at the L0 level, only space 6 in which three vertices exist together has a value of 1 and the remaining spaces are expressed to have a value of 0. At the L1 level, octree partitioning is performed only for the 6th space of the L0 level, and at the L1 level, only the 1st space with two vertices and the 7th space with 1 vertex has a value of 1 and the remaining spaces have a value of 0. It is expressed to have. Data bits for expressing up to the L1 level are equal to 00000100 01000001.

Even at the L2 level, the space containing the vertices can be subdivided by performing space division, but since the LoD (Level of Details) value is set to 1, it can be expressed only up to the L1 level. Accordingly, since the precision for the L2 level is abandoned, the coordinates of the vertices can be quantized.

Specifically, the coordinates of two of the three vertices may be set as the coordinates of the midpoint of space 1 of the L1 level, and the coordinates of the other vertex may be set as the coordinates of the midpoint of space 7 of the L1 level. .

In this way, the coordinates of two or more vertices may be set as coordinates of one vertex by quantization in the geometric information conversion unit 134. That is, since two or more vertices may be merged into one vertex, the number of vertices included in the geometric information of the 3D mesh model may decrease. If the number of vertices decreases, the connection information connecting the vertices may also be changed. . A method of updating the changed connection information will be described in the connection information remapping unit 140 to be described later.

Meanwhile, the geometric information conversion unit 134 does not have to use only an octree division or a K-d tree division method in order to reduce the amount of data representing the geometric information, but may use various other methods. For example, in order to reduce the amount of data, the geometric information conversion unit 134 simplifies the face constituting the 3D mesh model by merging the two vertices into one vertex or deleting the protruding vertex if the distance between the two vertices is less than a specific value. You may. When spatial division is not used in the geometric information conversion unit 134, voxelization in the voxelization unit 132 may be omitted.

The geometric information encoding unit 136 may compress the geometric information converted by the geometric information conversion unit 134 by using arithmetic coding or entropy coding techniques such as huffman and asymmetric numeral systems.

The connection information remapping unit 140 may update connection information. Specifically, the connection information remapping unit 140 updates connection information associated with a vertex that has been changed to another vertex, merged with another vertex, or disappeared by the quantization performed by the voxelizer 132 or the geometric information conversion unit 134 can do.

Regarding the update method, when the vertex is changed to another vertex in the process of compressing the geometric information, the connection information remapping unit 140 updates the corresponding vertex in the connection information and deletes the overlapping or non-existing side from the connection information. You can update the connection information by doing so.

4 to 7 will be described in connection with the connection information remapping unit 140.

4 is a diagram illustrating a change in connection information according to a change in geometric information.

Referring to FIG. 4, a vertex having an index of 1 (vtxId: 1), a vertex having an index of 2 (vtxId: 2), and a vertex having an index of 3 (vtxId: 3) become one new vertex (vtxId': 1). As they are merged (change of geometric information), the face with index 1 (faceId: 1), the face with index 2 (faceId: 2), and the face with index 3 (faceId: 3) disappear, and the remaining faces constitute the remaining faces. One vertex to be merged is changed to a merged vertex (vtxId': 1). (Change of connection information)

Here, when three vertices (vtxId: 1,2,3) are merged into one vertex (vtxId': 1), three vertices (vtxId: 1,2,3) are destroyed, and the destroyed vertices are newly created. One vertex (vtxId': 1) can be considered to have been changed, or the positions of three vertices (vtxId: 1,2,3) can be regarded as being changed to the position of one vertex (vtxId': 1).

In addition, here, the reason that three vertices (vtxId: 1,2,3) are merged into one vertex (vtxId': 1) is, for example, quantization performed by the voxelization unit 132 or the geometric information conversion unit 134. I can.

In addition, here, the reason that the face with the index of 1 (faceId: 1), the face with the index of 2 (faceId: 2), and the face with the index of 3 (faceId: 3) disappear is because at least two of the vertices constituting the triangle This is because the vertices are merged into one vertex and the face (triangle) is not formed.

In this way, when the geometric information is changed, the connection information may have to be changed, so when the vertex is changed to another vertex in the process of compressing the geometric information, the connection information remapping unit 140 updates the corresponding vertex from the connection information and If a face that constitutes the connection information due to merge or disappearance of a vertex exists or does not exist, the corresponding face is deleted from the connection information and the connection information is updated, so that the connection information before the geometric information change (three-dimensional mesh model prototype) is saved. As it is updated, there may not be a big difference from the original even after the connection information is updated.

5 is a diagram illustrating another example of a change in connection information according to a change in geometric information.

Referring to FIG. 5, as shown in FIG. 4, a vertex having an index of 1 (vtxId: 1), a vertex having an index of 2 (vtxId: 2), and a vertex having an index of 3 (vtxId: 3) have one new vertex (vtxId). ': 1) (change of geometric information), the face with index 1 (faceId: 1), the face with index 2 (faceId: 2) and the face with index 3 (faceId: 3) disappear. (Change of connection information)

However, unlike FIG. 4, in FIG. 5, there is only one surface except for the three surfaces that disappear (left drawing), so that three vertices (vtxId: 1,2,3) become one vertex (vtxId': 1). When merged, a vertex with an index of 1 (vtxId': 1) and a vertex with an index of 2 (vtxId': 2) may be connected by a line or disconnected. (Right drawing)

In the case of FIG. 5, the connection information remapping unit 140 merges three vertices (vtxId: 1,2,3) into one vertex (vtxId': 1) and has an index of 3 (faceId: 3). Since this line is deformed and the face (triangle) is no longer established (not established), the connection information about the face with index 3 (faceId: 3) can be deleted. Accordingly, the connection between the vertex with index 1 (vtxId': 1) and the vertex with index 2 (vtxId': 2) is disconnected.

However, if the vertex with index 1 (vtxId': 1) and the vertex with index 2 (vtxId': 2) are disconnected or connected with a straight line (right drawing), there will be a big difference from the original 3D mesh model (left drawing). Therefore, in order to maintain the circular shape as much as possible, the connection information remapping unit 140 may change a straight line generated by merging vertices into a plane.

For example, when the connection information remapping unit 140 has a face (faceId: 3) transformed into a straight line, the triangular shape is no longer established, and both ends of the straight line (vtxId': 1,2) are connected only by a straight line. Is connected to one of the vertices of both ends of the straight line (vtxId': 1,2), and searches for the vertex at the shortest distance, and the found vertex (vtxId': 4) and the vertices of both ends of the straight line (vtxId': 1) By connecting ,2), a new face (faceId': 4) can be created and inserted into the connection information.

In addition, the connection information remapping unit 140 may set different indexes at the vertices of the geometric information and manage the connection information using the indexes of the vertices. In this regard, FIGS. 6 and 7 will be described.

In addition, the connection information remapping unit 140 may generate an index mapping table for a vertex by receiving geometric information before quantization and geometric information after quantization from the voxelizer 132 or the geometric information conversion unit 134. . In this regard, FIGS. 6 and 7 will be described.

6 and 7 are diagrams illustrating a process of updating connection information by the connection information remapping unit 140 according to an exemplary embodiment.

6, the connection information remapping unit 140 according to an embodiment may set different indices for vertices constituting geometric information, and configure a mapping table between indexes of vertices before quantization and after quantization. I can.

In FIG. 6, a vertex with an index of 0 before quantization and a vertex with an index of 1 are merged with a vertex with an index of 0 after quantization, so that both vertices are set as a vertex with an index of 0. .

The connection information remapping unit 140 has the same structure as (0,0) for a vertex with index 0 and (1,0) for a vertex with index 1 by associating the indexes before and after quantization with respect to the two vertices. Data can be saved.

In FIG. 6, the connection information remapping unit 140 converts the index of the merged vertex (vertex with pre-quantization indexes 1, 3, and 5) to the index of the merge reference vertex (vertex with pre-quantization indexes 0, 2, and 4). In addition to mapping to, the index of the merge reference vertex (indexes 0, 2, 4) is reset to a small index.

That is, the connection information remapping unit 140 may reset the indexes of the merge reference vertices of 0, 2, and 4 before quantization to 0, 1, and 2 after quantization. This is to increase the compression rate of connection information composed of the index of the vertex by reducing the index.

Referring to FIG. 7, the connection information remapping unit 140 according to an embodiment may manage connection information using an index of a vertex and may update the connection information using an index mapping table for a vertex.

That is, the connection information remapping unit 140 includes the connection information of the surface with the index of 0 before remapping, and the connection information of the surface with the index of 0, 2, and 4 is composed of vertices with the indexes 0, 2, and 4. Connection information is changed to vertices with indexes of 0, 1, and 2.

The connection information remapping unit 140 uses the index mapping table to change the vertex index of each surface constituting the connection information, and then searches whether there are two or more surfaces with matching vertices constituting the surface. If there are two or more faces with the same vertex index, the duplicate faces can be removed.

That is, the connection information remapping unit 140 checks whether two or more faces having an index of 0, 1, and 2 of vertices constituting the face exist with respect to the face having index 0 after applying the index mapping table to the connection information. The connection information remapping unit 140 determines that the index 1 is an overlapping surface because the indexes of the vertices constituting the surface of the index 1 are 0, 1, and 2, which are identical to the indexes of the vertices of the surface of the index 0. Can be removed from.

In addition, the connection information remapping unit 140 determines whether the indexes of the vertices constituting each surface have different values for each surface (eg, a triangle) after the index mapping table is applied, and two or more If the vertices have the same index, it is determined that the face is not established, and the corresponding face can be deleted from the connection information. However, as shown in FIG. 5, in order to maintain the circle of the 3D mesh model as much as possible, a straight line may be changed to a surface.

Here, the inconsistency of a face may include not only a case where two or more vertices are merged into one vertex and a triangle is changed to a straight line or a point, but also a polygon with n vertices is changed to a polygon with fewer than n vertices. have. For example, for a polyhedral mesh model using a square as a basic unit, when vertices are merged and the square is changed to a triangle due to quantization, a face (rectangle) is not established.

On the other hand, the connection information remapping unit 140 may determine that the surface is not established without the need to change the index of the vertex and compare the index value, unlike the above. For example, when the protruding vertex is deleted in the geometric information conversion unit 134 to reduce the amount of data, the connection information remapping unit 140 changes the index of the deleted vertex to a null value, and then configures the surface. The connection information can be updated by directly deleting the face composed of the deleted vertices from the connection information, without having to compare whether the index values are different.

In this way, the connection information remapping unit 140 can quickly and efficiently update the connection information by setting different indexes at the vertices of the geometric information and managing the connection information using the indexes of the vertices.

The connection information compression unit 150 may include a connection information conversion unit 152 and a connection information encoding unit 154 and may compress connection information updated by the connection information remapping unit 140.

The connection information conversion unit 152 may convert the connection information updated by the connection information remapping unit 130 into a format with a small amount of data to be expressed. The connection information conversion unit 152 may use various methods for converting connection information, and the Edgebreaker method, which is a standard technology of MPEG, will be described as an example in FIG. 8.

The connection information encoding unit 154 may encode the geometric information converted by the connection information conversion unit 152. The connection information encoding unit 154 can use various methods to convert the connection information. Like the connection information conversion unit 152, the Edgebreaker method, which is a standard technology of MPEG, will be described as an example in FIG. 8.

8 is a diagram showing the Edgebreaker method.

Referring to FIG. 8, the Edgebreaker symbolizes connection information along an arrow using a triangle traversal encoding technique. In FIG. 8, a yellow triangle is symbolized as C, and a blue triangle is symbolized as R. Each of the symbols (C, L, E, R, S) is replaced with a predefined bit. In the left figure of Fig. 8, the connection information (triangle) is symbolized as CCRRRSLCRSERRELCRRRCRRRE, and these symbols are binarized into 00101101101100 ... 101111. These binarized symbols are compressed once again using an entropy coding technique.

Edgebreaker sequentially compresses the coordinates of the vertices constituting the triangle to be encoded in the process of iterative encoding of the connection information. That is, when encoding the first symbol C from the left of FIG. 8, the coordinates of vertices 1, 16, and 17 in the vicinity are compressed. When the second symbol C is encoded, since the coordinates of vertices 1 and 17 are already encoded, only the coordinates of vertex 18 are additionally compressed.

However, since the 3D mesh model compression system 100 has already completed the encoding of the coordinates of the vertices in the geometric information conversion unit 134, the connection information conversion unit 152 or the connection information encoding unit 154 Only the vertex index can be encoded without re-hatching the vertex coordinates. That is, when encoding the first symbol C, vertices having indices 1, 16, and 17 are encoded, and when encoding the second symbol C, only vertices having an index of 18 may be additionally encoded.

In addition, the connection information converter 152 or the connection information encoding unit 154 may encode a difference between the index values of the vertices instead of encoding the indexes of the vertices in the iterative encoding process. That is, only values of 1, 15, 1, and 1, which are differences between the indexes of the vertices that have been traversed in advance during the traversal encoding, can be sequentially encoded.

In this way, the connection information compression unit 150 compresses the connection information updated by the connection information remapping unit 140 using the index of the vertex or the difference value of the index of the vertex, thereby performing compression quickly and increasing the extrusion rate. Can be improved.

The color information compression unit 160 may be configured to include a color information conversion unit 162 and a color information encoding unit 164 and may compress color information.

The color information conversion unit 162 may convert the color information into a format with a small amount of data to be expressed. The conversion process of the color information conversion unit 162 may be affected by the conversion process of the geometric information conversion unit 134. Specifically, when the geometric information conversion unit 134 performs geometric information conversion, an expressible level (Level of Details) is determined, and the amount of color value may be determined according to this determination.

The color information conversion unit 162 may use Region-Adaptive Hierarchical Transform (RAHT) or a JPEG compression technique.

The color information encoding unit 164 may encode color information using an arithmetic coding technique or an entropy coding technique such as huffman and asymmetric numeral systems.

The first mode determination unit 170 may determine a compression mode of the 3D mesh model compression system 100. Specifically, the first mode determination unit 170 may be configured to include a memory in which the compression mode value is stored, and whether the connection information remapping unit 140 and the connection information compression unit 150 are executed according to the compression mode value. Can be determined.

Here, the compression mode may include, for example, a 3D mesh model compression mode or a 3D point cloud compression mode, and when the compression mode is set to the 3D point cloud compression mode, the connection information remapping unit 140 and the connection It may be controlled so that the information compression unit 150 is not performed. Specifically, since the 3D point cloud does not include connection information, compression of connection information is unnecessary, so in the 3D point cloud compression mode, the connection information remapping unit 140 and the connection information compression unit 150 may not be performed. have.

9 is a diagram illustrating a data flow of a 3D mesh model compression system in a 3D point cloud compression mode according to an embodiment.

Referring to FIG. 9, in the 3D point cloud compression mode according to an embodiment, the 3D mesh model compression system 100 includes (i) geometry among information on the 3D point cloud model input from the first input unit 110. Information is compressed through a coordinate conversion unit 120, a voxel conversion unit 132, a geometric information conversion unit 134, and a geometric information encoding unit 136, and (ii) color information is a coordinate conversion unit 120, a voxel conversion unit ( 132), a geometric information conversion unit 134, a color information conversion unit 162, and a color information encoding unit 164.

On the other hand, the 3D mesh model compression system 100 first compresses the geometric information, not the connection information, and updates the connection information in the process of compressing the geometric information or after entering the geometric information, and compresses the updated connection information. Not only 3D mesh model compression, but also 3D point cloud compression that does not require compression of connection information can be efficiently performed.

That is, when compression is performed in the 3D point cloud compression mode, the 3D mesh model compression system 100 may be a system that provides optimal performance for 3D point cloud compression.

On the other hand, when compression is performed in the 3D mesh model compression mode, the 3D mesh model compression system 100 may be a system that provides optimal performance for 3D mesh model compression.

The first output unit 180 may output compressed geometric information, compressed connection information, and the like through the first transmission/reception unit 185 or output to the first database 190 and store them.

The first transmission/reception unit 185 receives geometric information and connection information from another terminal to which the first input unit 110 is connected through a communication network, or the first output unit 180 receives compressed geometric information and a compressed connection to another terminal. Make it possible to transmit information, etc.

Here, the communication network may mean a broad concept network including a wired or wireless communication network, and the terminal is a server, laptop, mobile phone, smart phone (2G/3G/4G/LET, smart phone), PMP (Portable Media Player). ), PDA (Personal Digital Assistant), and Tablet PC (Tablet PC) may be any one.

The first database 190 may store input geometric information and connection information, or may store compressed geometric information and compressed connection information to be output.

This first database 190 is a concept including a computer-readable recording medium, and refers to not only a database of consultation, but also a database in a broad sense including data recording based on a file system, and even a simple set of logs. If data can be extracted by searching for this, it is included within the scope of the database in the present invention.

The first control unit 195 controls the overall operation of the 3D mesh model compression system 100, and the first input unit 110, the coordinate conversion unit 120, the geometric information compression unit 130, the connection information remapping unit (140), the connection information compression unit 150, the color information compression unit 160, the first mode determination unit 170, the first output unit 180, the first transmitting and receiving unit 185, and the first database 190 ) Can control the flow of control or data flow.

10 is a block diagram illustrating an exemplary 3D mesh model decompression system according to an embodiment.

11 is a diagram illustrating an exemplary data flow in a 3D mesh model compression system according to an embodiment.

Referring to FIG. 10, a 3D mesh model decompression system 200 according to an embodiment includes a second input unit 210, a geometric information decompression unit 220, a connection information decompression unit 230, and color information compression. A release unit 240, a coordinate restoration unit 250, a second mode determination unit 260, a second output unit 270, a second transmission/reception unit 280, a second database 290, and a second control unit 295 ) Can be included.

Referring to FIG. 11, the 3D mesh model decompression system 200 according to an embodiment includes information on the compressed 3D mesh model received from the second input unit 210, (i) geometric information is geometric information decoding. The compression is decompressed through the unit 222, the geometric information restoration unit 224, the coordinate restoration unit 250, and (ii) the connection information is a connection information decoding unit 232, a connection information restoration unit 234, and a coordinate restoration unit ( 250), and (iii) the color information is decompressed through the color information decoding unit 242, the color information restoration unit 244, and the coordinate restoration unit 250.

Hereinafter, each configuration will be described.

The second input unit 210 may receive compressed geometric information, compressed connection information, and compressed color information for the 3D mesh model through the second transmitter/receiver 280 or from the second database 290. .

Here, the compressed geometric information may be configured including the coordinates of the compressed vertex, and the compressed connection information may be configured including information obtained by compressing a set of faces composed of the index of the vertex.

The geometric information decompression unit 220 may include a geometric information decoding unit 222 and a geometric information restoration unit 224, and may restore the coordinates of a vertex from the compressed geometric information.

The geometric information decoding unit 222 may decode the encoded geometric information using arithmetic coding or entropy coding techniques such as huffman and asymmetric numeral systems.

The geometric information restoration unit 224 calculates the coordinates of a vertex by constructing an octree or a Kd-tree for geometric information expressed by an octree decomposition method or a Kd-tree decomposition method. Through this method, the coordinates of the vertices can be restored.

The connection information decompression unit 230 may be configured to include a connection information decoding unit 232 and a connection information restoration unit 234, and is compressed based on the coordinates of the vertices restored by the geometric information decompression unit 220. Connection information composed of the coordinates of the vertex can be restored from the connection information.

The connection information decoding unit 232 or the connection information restoration unit 234 may decode geometric information encoded using the Edgebreaker method, which is a standard technology of MPEG.

Also, the connection information restoration unit 234 may restore connection information composed of the coordinates of the vertex from the connection information decoded based on the coordinates of the vertex restored by the geometric information decompression unit 220.

The color information decompression unit 240 may include a color information decoding unit 242 and a color information restoration unit 244, and may decompress the compressed color information.

The color information decoding unit 242 can decode the encoded color information using an arithmetic coding technique or an entropy coding technique such as huffman and asymmetric numeral systems, and the color information restoration unit 244 can decompress the color information. .

The coordinate restoration unit 250 may restore a vertex included in the geometric information to its original coordinates.

The second mode determination unit 260 may determine a decompression mode of the 3D mesh model decompression system 200. Specifically, the second mode determination unit 260 may include a memory in which a decompression mode value is stored, and whether to perform the connection information decompression unit 230 may be determined according to the decompression mode value.

Here, the decompression mode may include, for example, a 3D mesh model decompression mode or a 3D point cloud decompression mode, and when the decompression mode is set to the 3D point cloud decompression mode, the connection information decompression unit It can be controlled so that 230 is not performed.

12 is a diagram illustrating a data flow of a 3D mesh model decompression system in a 3D point cloud decompression mode according to an embodiment.

Referring to FIG. 12, in the 3D point cloud decompression mode according to an embodiment, the 3D mesh model decompression system 200 includes information on the 3D point cloud model received from the second input unit 210. ) The geometric information is decompressed through the geometric information decoding unit 222, the geometric information restoration unit 224, and the coordinate restoration unit 250, and (ii) the color information is color information decoding unit 242, the color information restoration unit ( 244), the compression is decompressed through the coordinate restoration unit 250.

The second output unit 270 may output the decompressed geometric information, the decompressed connection information, and the like through the second transmission/reception unit 180 or output to the second database 290 for storage.

The second transmission/reception unit 285 receives compressed geometric information and compressed connection information from another terminal connected to a communication network by the second input unit 210, or the second output unit 270 decompresses the geometry at another terminal. Information, decompressed connection information, etc. can be transmitted.

Here, the communication network may mean a broad concept network including a wired or wireless communication network, and the terminal is a server, laptop, mobile phone, smart phone (2G/3G/4G/LET, smart phone), PMP (Portable Media Player). ), PDA (Personal Digital Assistant), and Tablet PC (Tablet PC) may be any one.

The second database 290 may store received compressed geometric information and compressed connection information, or may store decompressed geometric information and decompressed connection information to be output.

This second database 290 is a concept including a computer-readable recording medium, and refers to not only a database of consultation, but also a database in a broad sense including data recording based on a file system, and even a simple set of logs. If the data can be extracted by searching for it, it is included within the scope of the database in the present invention.

The second control unit 295 controls the overall operation of the 3D mesh model decompression system 200, and the second input unit 210, the geometric information decompression unit 220, the connection information decompression unit 230, and color Control flow between the information decompression unit 240, the coordinate restoration unit 250, the second mode determination unit 260, the second output unit 270, the second transmission/reception unit 280 and the second database 290, or You can control the data flow.

13 is a flowchart illustrating a method of compressing a 3D mesh model according to an embodiment of the present invention.

13, a 3D mesh model compression method 300 according to an embodiment includes a first input step (S310), a geometric information compression step (S320), a connection information remapping step (S330), and a connection information compression step. It may be configured including (S340).

In the first input step (S310), the 3D mesh model compression system 100 receives geometric information, connection information, and color information for the 3D mesh model through the first transmission/reception unit 185 or the first database 190 ) Can be input.

이하([0,

])인 정수 값을 가지도록 양자화를 수행할 수 있다. 이 때에, 3차원 메쉬모델의 기하정보에 포함된 정점의 개수가 감소할 수 있는데 정점의 개수가 감소하면 정점을 연결한 연결정보도 변경될 수 있다. 변경된 연결정보를 갱신하는 방법은 후술할 연결정보 재맵핑단계(S330)에서 살펴본다.In the geometric information compression step (S320), the three-dimensional mesh model compression system 100 is the coordinate of the vertex is 0 or more

Less than ([0,

Quantization can be performed to have an integer value of ]). At this time, the number of vertices included in the geometric information of the 3D mesh model may decrease. If the number of vertices decreases, the connection information connecting the vertices may also be changed. A method of updating the changed connection information will be described in the connection information remapping step (S330) to be described later.

In addition, the 3D mesh model compression system 100 can compress geometric information by efficiently expressing quantized geometric information. The 3D mesh model compression system 100 may use an octree decomposition method or a Kd-tree decomposition method in order to efficiently express geometric information.

In this case, coordinates of two or more vertices may be set as coordinates of one vertex by quantization. That is, since two or more vertices may be merged into one vertex, the number of vertices included in the geometric information of the 3D mesh model may decrease. If the number of vertices decreases, the connection information connecting the vertices may also be changed. . A method of updating the changed connection information will be described in the connection information remapping step (S330) to be described later.

In addition, the 3D mesh model compression system 100 may compress the converted geometric information by using arithmetic coding or entropy coding techniques such as huffman and asymmetric numeral systems.

In the connection information remapping step (S330), the 3D mesh model compression system 100 may update the connection information. Specifically, the 3D mesh model compression system 100 may update connection information associated with a vertex that has been changed to another vertex, merged with another vertex, or disappeared by quantization.

Regarding the update method, the 3D mesh model compression system 100 updates the corresponding vertex in the connection information when a vertex is changed to another vertex in the process of compressing the geometric information, and duplicates existing or non-conforming surfaces in the connection information. Connection information can be updated by deleting.

In addition, the 3D mesh model compression system 100 may set different indexes for vertices of geometric information and manage connection information using the vertices index.

In addition, the 3D mesh model compression system 100 may receive geometric information before quantization and geometric information after quantization to generate an index mapping table for vertices.

In the connection information compression step (S340), the 3D mesh model compression system 100 converts the updated connection information into a format with a small amount of data to be expressed. The 3D mesh model compression system 100 converts the connection information to MPEG Various methods, such as the Edgebreaker method, which is a standard technology of, can be used.

In addition, the 3D mesh model compression system 100 may encode the converted geometric information.

14 is a flowchart illustrating a method of decompressing a 3D mesh model according to an embodiment of the present invention.

Referring to FIG. 14, a method 400 for decompressing a 3D mesh model according to an embodiment includes a second input step (S410), a geometric information decompression step (S420), and a connection information decompression step (S430). Can be configured.

In the second input step (S410), the 3D mesh model decompression system 200 transmits compressed geometric information, compressed connection information, and compressed color information for the 3D mesh model through the second transmission/reception unit 280. It may be input or may be input from the second database 290.

Here, the compressed geometric information may be configured including the coordinates of the compressed vertex, and the compressed connection information may be configured including information obtained by compressing a set of faces composed of the index of the vertex.

In the geometric information decompression step (S420), the 3D mesh model decompression system 200 can decode the encoded geometric information using arithmetic coding or entropy coding techniques such as huffman and asymmetric numeral systems, and octree partitioning (Octree). The coordinates of the vertex can be restored through a method such as calculating the coordinates of the vertex by constructing an octree or a Kd-tree for geometric information expressed by the decomposition method or Kd-tree decomposition method.

In the connection information decompression step (S430), the 3D mesh model decompression system 200 can decode the geometric information encoded using the Edgebreaker method, which is a standard technology of MPEG, and is restored in the geometric information decompression step (S420). Connection information composed of the coordinates of the vertex may be restored from the connection information decoded based on the coordinates of the vertex.

As described above, although it has been described with reference to the preferred embodiments of the present application, those skilled in the art will variously modify the present application within the scope not departing from the spirit and scope of the present invention described in the following claims. And it will be appreciated that it can be changed.

100: 3D mesh model compression system
110: first input unit 120: coordinate conversion unit
130: geometric information compression unit 140: connection information re-mapping unit
150: connection information compression unit 170: first mode determination unit
200: 3D mesh model decompression system
210: second input unit 220: geometric information decompression unit
230: connection information decompression unit 250: coordinate restoration unit
260: second mode determination unit

Claims (8)

A first input unit for receiving geometric information and connection information for the 3D mesh model;
The geometric information is configured to include the coordinates of the vertices, and the connection information is configured to include a connection relationship between the vertices constituting the plane,
A geometric information compression unit compressing the geometric information;
A connection information remapping unit for updating the connection information; And
And a connection information compression unit for compressing the updated connection information,
The geometric information compression unit includes a geometric information conversion unit for compressing to reduce the number of vertices included in the geometric information,
The connection information remapping unit generates an index mapping table for matching a vertex index before being compressed by the geometric information conversion unit and a vertex index compressed by the geometric information conversion unit,
The 3D mesh model compression system for compressing the connection information using the index mapping table.
The method of claim 1,
The connection information remapping unit updates connection information associated with a vertex that has been changed to another vertex, merged with another vertex, or disappeared by the geometric information conversion unit.
The method of claim 1,
The connection information remapping unit updates the connection information by updating the corresponding vertex from the connection information when a vertex is changed to another vertex in the process of compressing the geometric information, and deleting the overlapping or non-conforming surface from the connection information. 3D mesh model compression system characterized by.
The method of claim 3,
The connection information remapping unit sets different indexes at the vertices of the geometric information and manages the connection information using the index,
The 3D mesh model compression system, wherein the connection information compression unit compresses the updated connection information using the index or a difference value of the index.
The method of claim 1,
The 3D mesh model compression system includes a first mode determining unit for determining a compression mode,
3D mesh model compression system, characterized in that whether to perform the connection information remapping unit and the connection information compression unit is determined according to the compression mode.
A second input unit for receiving compressed geometric information and compressed connection information for the 3D mesh model;
The compressed geometric information includes coordinates of a vertex compressed to reduce the number of vertices included in the geometric information, and the compressed connection information includes information obtained by compressing a set of faces consisting of the index of the vertex. Become,
A geometric information decompression unit for restoring the coordinates of a vertex from the compressed geometric information;
A connection information remapping unit for updating the connection information; And
And a connection information decompression unit for restoring connection information composed of the coordinates of the vertex from the compressed connection information based on the coordinates of the restored vertex,
The geometric information decompression unit is a three-dimensional mesh model decompression system for restoring geometric information using an index mapping table that matches a vertex index before compression and a vertex index after compression.
A first input step of receiving geometric information and connection information for a 3D mesh model;
The geometric information is configured to include the coordinates of the vertices, and the connection information is configured to include a connection relationship between the vertices constituting the plane,
A geometric information compression step of compressing the geometric information by a geometric information compression unit;
A connection information remapping step of updating the connection information by a connection information remapping unit; And
And a connection information compression step of compressing the updated connection information by a connection information compression unit,
Compressing to reduce the number of vertices included in the geometric information by a geometric information conversion unit included in the geometric information compression unit,
The connection information remapping unit performs the step of generating an index mapping table for matching a vertex index before being compressed by the geometric information conversion unit and a vertex index compressed by the geometric information conversion unit,
The 3D mesh model compression method in which the connection information compression unit compresses connection information using the index mapping table.
A second input step of receiving compressed geometric information and compressed connection information for the 3D mesh model;
The compressed geometric information includes coordinates of a vertex compressed to reduce the number of vertices included in the geometric information, and the compressed connection information includes information obtained by compressing a set of faces consisting of the index of the vertex. Become,
A geometric information decompression step of restoring the coordinates of a vertex from the compressed geometric information by a geometric information decompression unit;
A connection information remapping step of updating the connection information by a connection information remapping unit; And
And a connection information decompression step of restoring connection information composed of the coordinates of the vertex from the compressed connection information based on the coordinates of the restored vertex by the connection information decompression unit,
The method of decompressing a 3D mesh model, wherein the geometric information decompression unit restores geometric information using an index mapping table that matches a vertex index before compression and a vertex index after compression.

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