KR101086772B1 - Method and apparatus for 3d mesh compression based quantization - Google Patents

Abstract

The present invention relates to a three-dimensional mesh compression apparatus and method based on the quantization technique, the disclosed compression apparatus analyzes the data of the input three-dimensional mesh model vertex information, property information indicating the characteristics of the three-dimensional mesh model and three-dimensional mesh A data analyzer for separating connection information between vertices constituting the model, a mesh model quantizer for generating quantized vertex information, property information, and connection information using vertex information, property information, and connection information, and quantized connection A decision bit encoder for encoding the quantized vertex information, the attribute information, and the connection information using the calculated decision bit after calculating the decision bit using the information, and quantizing the connection information without performing a phase incision. After calculating the decision bit using the concatenated connection information, the data is encoded using the decision bit. As a result, the compression speed is improved by improving the complexity of data compression for the 3D mesh model, and the compression 3D model can be quickly and accurately restored according to the improvement of the compression complexity, thereby improving the recovery efficiency of the compressed data. .

Image Compression, 3D Mesh Model, Decision Bit Coding

Description

3D mesh compression apparatus and method based on quantization technique {METHOD AND APPARATUS FOR 3D MESH COMPRESSION BASED QUANTIZATION}

The present invention relates to image compression, and more particularly, quantized vertex information, property information and connectivity information of a 3D mesh model to be allocated using quantized connection information. The present invention relates to a three-dimensional mesh compression apparatus and method based on a quantization technique for encoding quantized vertex information, attribute information, and connection information using a decision bit after calculating a bit (decision bit).

The present invention is derived from the research conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Telecommunications Research and Development. Development].

Currently, triangular mesh is widely used as a method of representing 3D images in the field of computer graphics. The triangular mesh image is composed of the position information of the vertices forming the triangle and the connection information between the vertices due to the non-uniform structure, so that the amount of data is much larger than the two-dimensional image having the uniform structure.

Therefore, many studies have been actively conducted to solve the problem of storing and transmitting a triangle mesh image.

As such, the 3D graphics field has been widely used in recent years, but its use range is limited due to the large amount of information.

This assumes that the vertex information of the 3D mesh model is represented by 32-bit floating point, and 96 bits, that is, 12 bytes of memory space are required to represent one vertex information.

This requires 120 KB if the 3D model is represented by 10,000 vertices with only vertex information, and 1.2 MB of memory if represented by 100,000 vertices.

In addition, since the connection information allows two or more overlaps, very much memory is required to store the 3D model by the polygon mesh.

Therefore, the enormous amount of such information has led to the need for encoding in the compression of 3D images. To this end, MPEG-4 (Moving Picture Expert Group-4)-3D Mesh Coding has been adopted as a standard of ISO / IEC (International Organization for Standardization / International Electrotechnical Compression) in the field of 3 Dimensional Graphics Compression (3DGC). : 3DMC) method encodes and decodes the mesh information of a three-dimensional model represented by an indexed faceset (IFS) file in a Virtual Reality Modeling Language (VRML) file. To improve the transmission efficiency.

1 is a block diagram of a conventional three-dimensional mesh coding encoding apparatus.

Referring to FIG. 1, the conventional 3D mesh coding encoding apparatus 110 includes a topological surgery for decomposing a 3D mesh model, which is original data including vertex information, connection information, and attribute information, into a 2D mesh structure. TS) module 111, vertex information encoding module 112 for encoding vertex information decomposed into a two-dimensional mesh structure, connection information encoding module 113 for encoding connection information decomposed into a two-dimensional mesh structure, two-dimensional mesh The result encoded by the attribute information encoding module 114, the vertex information encoding module 112, the connection information encoding module 113, and the attribute information encoding module 114, which encodes the attribute information decomposed into a structure, is compressed. And an entropy encoder module 115 for generating a dimensional mesh coding bitstream.

The main feature of the 3D mesh coding encoding performed by the 3D mesh coding encoding apparatus 110 is a phase cutting operation performed by the phase cutting module 111 to maximize the compression ratio. The phase cutting operation is a method of decomposing a three-dimensional model into a two-dimensional mesh structure by assuming that a mesh of a given three-dimensional model is topologically identical to a sphere, and then cutting the mesh according to a cutting edge.

FIG. 2 is a block diagram of a 3D mesh coding decoding apparatus corresponding to FIG. 1.

Referring to FIG. 2, the 3D mesh coding decoding apparatus 210 includes an entropy decoding module 211, a vertex information decoding module 212, a connection information decoding module 213, an attribute information decoding module 214, and a phase synthesis. Module 215 to recover three-dimensional model data from the encoded three-dimensional mesh coding bitstream.

FIG. 3 illustrates the overall structure of a coded bitstream of mesh information of the 3D model generated by FIG. 1.

Referring to FIG. 3, a coded bitstream of mesh information of a three-dimensional model includes a triangular tree (TT) 303 including a triangular minimum elongation graph of a binary tree structure consisting of triangular strips, and information about a triangular tree. A vertex graph (VG) 301 representing a value (Triangle Data (TD)) 305 and a path for cutting the mesh of the three-dimensional model as a connection structure between the vertices.

4A to 4D illustrate a process of performing phase cutting on a mesh of a conventional 3D model.

First, as shown in FIG. 4A, the mesh of the three-dimensional model is cut along a cutting edge defined by a thick line, and then a triangular tree is formed as shown in FIG. 4B.

In general, for fast processing of graphics, the modeled unit is a triangle, and it is preferable that the triangles are connected to each other in the form of strips or fans, rather than randomly configured. In addition, the more the symbol is repeatedly represented, the more excellent the data compression ratio is. Therefore, in the phase cutting of the mesh of the conventional 3D model, the mesh of the 3D model is cut along the cutting edge as shown in FIG. Construct a tree.

Then, as shown in Figure 4c, the reference point is selected in the triangle tree, and the vertex graph is formed by connecting the selected reference point and the outermost vertex of the branched triangle.

Then, as shown in FIG. 4D, a bounding loop is formed using the vertex graph.

As described above, in the current MPEG-4 three-dimensional mesh coding method, in order to decompose a three-dimensional model represented by an indexed faceset node, a phase incision process is performed to decompose the three-dimensional model's mesh structure into a two-dimensional mesh map structure. Rough

As described above, the three-dimensional mesh structure is represented by a vertex graph and a triangular tree structure to guarantee a very high compression ratio for the three-dimensional model, but this has a problem of changing the position information of the original vertex of the three-dimensional model.

That is, after undergoing a phase cutting process, the position information of the vertices is newly indexed by the encoding side and transmitted to the decoding side for higher compression ratio.

For this reason, since the decoder side does not know the original position information of the vertices of the 3D model, when the order information of the vertices such as animation is used, the current 3D mesh coding method cannot support this.

The process of decomposing three-dimensional connection information and generating two-dimensional mesh maps, triangle trees, and vertex graphs from a three-dimensional mesh is an efficient way to increase the compression rate. As the process takes up a large part of the complexity, the phase incision process is very complicated and consumes time and resources.

As described above, the compression of the mesh information of the three-dimensional model according to the prior art guarantees a very high compression ratio for the three-dimensional model by representing the three-dimensional mesh structure as a vertex graph and a triangular tree structure, but the original vertex of the three-dimensional model There is a problem of changing the location information, and the phase cutting process is very complicated in the entire compression process, so there is a problem in that time and resource consumption are large.

The present invention has been proposed to solve the problems of the prior art, and quantizes vertex information, property information, and connection information of a three-dimensional mesh model without performing a phase incision to calculate decision bits using quantized connection information. Later, by encoding the quantized vertex information, the attribute information and the connection information using the decision bit to provide a three-dimensional mesh compression apparatus that can improve the compression speed by improving the complexity of data compression for the three-dimensional mesh model.

In addition, the present invention provides a compression method of a three-dimensional mesh model using a three-dimensional mesh compression apparatus.

The present invention also provides a recording medium recorded by a program that can perform a three-dimensional mesh compression method on a computer.

As a first aspect of the present invention, a three-dimensional mesh compression apparatus based on a quantization technique analyzes data of an input three-dimensional mesh model and vertex information, attribute information representing characteristics of the three-dimensional mesh model, and the three-dimensional mesh model. A data analyzer for separating connection information between constituent vertices, a mesh model quantization unit for generating quantized vertex information, property information, and connection information using the vertex information, property information, and connection information, and the quantized connection And a decision bit encoder for encoding the quantized vertex information, the attribute information, and the connection information using the determined decision bit after calculating the decision bit using the information.

Here, the data analysis unit includes a calculation unit for calculating the complexity of the three-dimensional mesh model, the calculation unit, based on a result of comparing the complexity value of the calculated three-dimensional mesh model and a preset complexity value Split a 3D mesh model into a plurality of partial meshes. The complexity is determined according to the number of facesets forming the three-dimensional mesh model. The connection information is represented by an index list in which a plurality of vertex information forms one polygon. The attribute information includes normals, colors, and texture coordinates of the 3D mesh model made of the polygon. The data analyzer includes a header that stores data about vertex information, attribute information, and connection information of the 3D mesh model.

According to a second aspect of the present invention, a three-dimensional mesh compression method based on a quantization technique analyzes data of an input three-dimensional mesh model and vertex information, attribute information representing characteristics of the three-dimensional mesh model, and the three-dimensional mesh model. Separating connection information between constituent vertices, generating quantized vertex information, attribute information, and connection information using the vertex information, attribute information, and connection information, and determining using the quantized connection information. Encoding the quantized vertex information, the attribute information, and the connection information using the determined bits calculated after calculating a bit.

The separating of the connection information between the vertices may include calculating a complexity of the 3D mesh model based on a result of comparing the calculated complexity value of the 3D mesh model and a preset complexity value. Dividing the three-dimensional mesh model into a plurality of partial meshes. The complexity is determined according to the number of facesets forming the three-dimensional mesh model. The connection information is represented by an index list in which a plurality of vertex information forms one polygon. The attribute information includes normals, colors, and texture coordinates of the 3D mesh model made of the polygon. Separating the connection information between the vertices includes storing data about vertex information, property information, and connection information of the 3D mesh model.

As a third aspect of the present invention, there is provided a recording medium having a computer program recorded thereon which performs a three-dimensional mesh compression method based on the above quantization technique.

According to the present invention, quantized vertex information, attribute information, and connection information of a three-dimensional mesh model without performing a phase incision, and after calculating the decision bit using the quantized connection information, the quantized vertex information using the decision bit. By encoding the attribute information and the connection information, the compression speed is improved by improving the complexity of data compression for the 3D mesh model.

In addition, since the compressed three-dimensional model can be quickly and accurately restored according to the improvement of the compression complexity, the recovery efficiency of the compressed data is also improved.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, embodiments of the present invention illustrated below may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the invention are provided to more fully illustrate the invention to those skilled in the art.

5 is a block diagram of a three-dimensional mesh compression apparatus based on a quantization technique according to the present invention.

Referring to FIG. 5, the 3D mesh compression apparatus according to the present invention includes a data analyzer 510, a mesh model quantizer 520, and a decision bit encoder 530.

In the apparatus for compressing a 3D mesh model according to the present invention, the data analyzer 510 analyzes data of an input 3D mesh model and vertices information 511 inherent to the mesh model and peculiar characteristics of the 3D mesh model. The attribute information 512 representing the symbol information and the connection information 513 between the vertices constituting the 3D mesh model are separated.

Among these, the vertex information 511 may be represented by coordinate information indicating the three-dimensional position of the vertex constituting the three-dimensional mesh model. Coordinate information may be expressed in three-dimensional coordinates represented by floating point, and is represented by coordinates having a real value on each axis aligned with each axis of x, y, and z.

The attribute information 512 may include normals, colors, and texture coordinates of a faceset constituting the 3D mesh model.

The connection information 513 may be expressed as an index list in which three or more vertex information forms a polygon, which will be referred to as an indexed faceset or a faceset in the present invention.

The data analyzer 510 may include a calculator (not shown) that calculates a complexity of the 3D mesh model, and the calculator may be implemented by, for example, a microprocessor. The microprocessor compares the complexity value of the three-dimensional mesh model with the externally set complexity value, and when the complexity value of the three-dimensional mesh model exceeds the externally set complexity value, Can be split into partial meshes. In addition, the data analyzer 510 may include a header (not shown) that stores data about vertex information, attribute information, and connection information of the 3D mesh model.

Substantially, when the 3D mesh model is represented by a significant number of vertices, there is a possibility that an error occurs in encoding due to an overload in the compression apparatus of the 3D mesh model due to an excessive amount of computation in the process of encoding the 3D mesh model. In order to prevent the encoding speed from being significantly reduced, when the complexity value is externally set, the partial compression may be divided into a plurality of partial meshes to prevent the compression apparatus from overloading and reducing the computation speed.

The complexity may be determined according to the number of facesets forming the 3D mesh model, and may be variously modified according to the use environment and the embodiment of the compression apparatus.

Meanwhile, the mesh model quantization unit 520 may extract vertex information 511, attribute information 512, and connection information 513 between vertices of the 3D mesh model analyzed by the data analyzer 510. The quantized vertex information, the attribute information, and the connection information may be generated.

The equation for performing quantization on each value in the mesh model quantization unit 520 may be expressed as in Equation 1 below.

In Equation 1, floor [] denotes a rounding operation, Xi denotes a quantizer input value, and t denotes a quantization parameter. max and min represent the maximum and minimum values of the input

연산을 하여 결정 비트를 계산하며, 계산된 결정 비트를 이용하여 양자화된 정점 정보, 속성 정보 및 연결 정보를 부호화하여 부호화된 데이터를 비트스트림 형태로 출력한다. 여기서 ceil[]은 올림 연산을 의 미하고, N은“정점의 개수”의 값을 가진다.In addition, the decision bit encoder 530 may determine the number of connection information quantized by the mesh model quantizer 520.

The operation calculates the decision bit by using the operation, and encodes the quantized vertex information, the attribute information, and the connection information using the calculated decision bit, and outputs the encoded data in the form of a bitstream. Where ceil [] means the rounding operation and N has the value of "number of vertices".

6 illustrates an embodiment of a quantization method applied to the present invention.

As shown in FIG. 6, if the minimum value is -0.5837 and the maximum value is 0.8576, the size of the entire section becomes 0.8576-(−0.5837) = 1.4413. If the quantization level is 10 for the entire interval, when 1.1443, the size of the entire interval, is divided into 1024 intervals, the size of one interval is 0.0019, and the value of -0.1849 becomes 283 by the calculation method of Equation 1.

6 is a result of calculating a quantization value of -0.1849, and the theorem of Equation 1 is a generalized expression by applying respective quantization levels for each axis of x, y, and z.

7 is a flowchart illustrating a compression method of a 3D mesh model according to the present invention.

Referring to FIG. 7, first, vertex information unique to the 3D mesh model, attribute information representing characteristics of the 3D mesh model, and connection information between vertices constituting the 3D mesh model from the input 3D mesh model Separate (S610).

That is, the 3D mesh model is composed of vertex information, attribute information, and connection information. Among them, the vertex information may be represented by coordinate information indicating the three-dimensional position of the vertex constituting the three-dimensional mesh model. Coordinate information may be expressed in three-dimensional coordinates expressed in floating point, and is expressed in coordinates having a real value in each axis aligned with each axis of x, y, and z.

The attribute information may include normals, colors, and texture coordinates of a face set constituting the 3D mesh model.

In addition, the connection information may be expressed as an index list in which three or more vertex information forms one polygon, which may be referred to as an indexed faceset.

Here, the separating of the connection information between the vertices may include storing data on the vertex information, the attribute information, and the connection information of the 3D mesh model.

The step of separating the connection information between the vertices may include calculating a complexity of the 3D mesh model, and when the complexity value of the calculated 3D mesh model exceeds a complexity value preset by the user. The method may further include dividing the model into a plurality of partial meshes.

As described above, if the three-dimensional mesh model is represented by a significant number of vertices, the encoding apparatus may overload the compression apparatus of the three-dimensional mesh model due to an excessive amount of computation in the process of encoding the three-dimensional mesh model, thereby causing an error in encoding. In order to prevent the encoding speed from being significantly reduced, when exceeding a complexity value previously set externally, it may be divided into a plurality of partial meshes so as to prevent an overload of the compression device and a reduction in arithmetic speed.

The complexity may be determined according to the number of facesets forming the 3D mesh model, and may be variously modified according to the use environment and the embodiment of the compression apparatus.

Next, the quantized vertex information, the attribute information, and the connection information are generated using the vertex information, the attribute information of the separated three-dimensional mesh model, and the connection information between the vertices of the three-dimensional mesh model. The equation for performing quantization for each value may be expressed as in Equation 1 above, and generates quantized vertex information, attribute information, and connection information according to the quantization level (S620).

연산을 하여 결정 비트를 계산하며, 계산된 결정 비트를 이용하여 양자화된 정점 정보, 속성 정보 및 연결 정보를 부호화하여 부호화된 데이터를 비트스트림 형태로 출력한다(S630).Finally, for the number of quantized connection information

The operation calculates the decision bit, encodes the quantized vertex information, the attribute information, and the connection information using the calculated decision bit, and outputs the encoded data in the form of a bit stream (S630).

Three-dimensional mesh compression method based on the quantization technique according to the present invention and each step of making it can be implemented in a variety of software or hardware using a general programming method is easy for those of ordinary skill in the art It can be done.

In addition, the three-dimensional mesh compression method based on the quantization technique of the present invention and each of the steps thereof may be implemented as computer readable codes on a computer readable recording medium. Computer-readable recording media include all types of recording devices that store data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, CD-RW, magnetic tape, floppy disks, HDDs, optical disks, magneto-optical storage devices, and carrier wave (eg, Internet It also includes the implementation in the form of (transmission through). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

It will be appreciated by those skilled in the art that the present invention described through the embodiments can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. Examples included in the above description are introduced for the understanding of the present invention, and these examples do not limit the spirit and scope of the present invention. It will be apparent to those skilled in the art that various embodiments of the present invention in addition to the above examples are possible. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a block diagram of a conventional three-dimensional mesh coding encoding apparatus.

FIG. 2 is a block diagram of a 3D mesh coding decoding apparatus corresponding to FIG. 1. FIG.

3 is a diagram showing the overall structure of a coded bitstream of mesh information of the three-dimensional model generated by FIG.

4A through 4D are diagrams illustrating a process of performing phase cutting on a mesh of a conventional three-dimensional model.

5 is a block diagram of a three-dimensional mesh compression apparatus based on a quantization technique according to the present invention.

6 is a diagram illustrating an embodiment of a quantization method applied to the present invention.

7 is a flowchart of a compression method of a three-dimensional mesh model based on a quantization technique according to the present invention.

Claims (13)

A data analysis unit for analyzing the data of the input 3D mesh model to separate vertex information, attribute information representing characteristics of the 3D mesh model, and connection information between vertices constituting the 3D mesh model; A mesh model quantizer configured to generate quantized vertex information, attribute information, and connection information using the vertex information, attribute information, and connection information; A decision bit encoder configured to calculate a decision bit using the quantized connection information and then encode the quantized vertex information, attribute information, and connection information using the calculated decision bit. 3D mesh compression apparatus based on a quantization technique comprising a. The method of claim 1, The data analysis unit includes a calculation unit for calculating the complexity of the three-dimensional mesh model, The calculating unit may divide the three-dimensional mesh model into a plurality of partial meshes based on a result of comparing the calculated complexity value of the three-dimensional mesh model with a preset complexity value. 3D mesh compression device based on quantization technique. The method of claim 2, The complexity is determined according to the number of facesets forming the three-dimensional mesh model. 3D mesh compression device based on quantization technique. The method of claim 1, The connection information is represented by an index list in which a plurality of vertex information forms one polygon. 3D mesh compression device based on quantization technique. The method of claim 4, wherein The attribute information includes normals, colors, and texture coordinates of the 3D mesh model composed of the polygons. 3D mesh compression apparatus based on a quantization technique comprising a. The method of claim 1, The data analyzer includes a header for storing data about vertex information, property information, and connection information of the 3D mesh model. 3D mesh compression apparatus based on a quantization technique comprising a. Analyzing the data of the input 3D mesh model to separate vertex information, attribute information representing characteristics of the 3D mesh model, and connection information between vertices constituting the 3D mesh model; Generating quantized vertex information, attribute information, and connection information using the vertex information, the attribute information, and the connection information; Calculating a decision bit using the quantized connection information and encoding the quantized vertex information, attribute information, and connection information using the calculated decision bit. 3D mesh compression method based on the quantization technique comprising a. The method of claim 7, wherein Separating the connection information between the vertices, Calculating a complexity of the three-dimensional mesh model; Dividing the three-dimensional mesh model into a plurality of partial meshes based on a result of comparing the calculated complexity value of the three-dimensional mesh model with a preset complexity value 3D mesh compression method based on the quantization technique comprising a. The method of claim 8, The complexity is determined according to the number of facesets forming the three-dimensional mesh model. 3D mesh compression method based on quantization technique. The method of claim 7, wherein The connection information is represented by an index list in which a plurality of vertex information forms one polygon. 3D mesh compression method based on quantization technique. 11. The method of claim 10, The attribute information includes normals, colors, and texture coordinates of the 3D mesh model composed of the polygons. 3D mesh compression method based on the quantization technique comprising a. The method of claim 7, wherein The separating of the connection information between the vertices may include storing data about vertex information, property information, and connection information of the 3D mesh model. 3D mesh compression method based on the quantization technique comprising a. A recording medium on which a computer program for performing a three-dimensional mesh compression method based on the quantization technique according to any one of claims 7 to 12 is recorded.

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