Three-dimensional grid lossless compression judgment method and device

Abstract

The invention relates to a three-dimensional grid lossless compression judgment method and device, and the method comprises the steps: carrying out the prior comparison of a to-be-matched grid and a comparison grid, judging whether the prior comparison results of the to-be-matched grid and the comparison grid are consistent, and if not, enabling the two grids to be not matched; if yes, the connection relation between the to-be-matched grid and the comparison grid is compared, and the matching result of the two grids is determined. According to the three-dimensional grid lossless compression judgment method, judgment on the grid connection relation is added, judgment on the grid connection relation in lossless measurement is perfected, and completeness of lossless grid measurement is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of lossless grid compression detection and measurement, and in particular relates to a three-dimensional grid lossless compression determination method and device. Background Art

[0002] Existing lossless quality measures use pixel-by-pixel and vertex-by-vertex comparison methods to determine whether the texture maps and mesh information of two meshes are the same. In terms of texture maps, when the sizes of the two texture maps are the same, the pixel values ​​of the texture maps of the two meshes are compared pixel by pixel to see if they are consistent. In terms of mesh information, existing lossless quality measures assume that geometric coordinates and texture coordinates share a set of connectivity relationships. When the number of triangles in the two meshes is the same, the triangles are taken out one by one in the original mesh according to the input order of the triangles, and the triangles with consistent information are searched in the unvisited triangles of the comparison mesh. If the corresponding triangle is found, the triangle is marked as visited in the comparison mesh. Among them, the triangles with consistent information refer to those with the same vertex information and consistent normal vectors. Vertex information contains all the information of the input mesh vertices, such as geometric coordinates, texture coordinates, vertex colors, and normal vectors. If any judgment result in the texture map or mesh information shows inconsistency, the two meshes are considered to be not exactly the same.

[0003] The existing technology can only judge the vertex information of the mesh, but cannot judge the connection relationship of the mesh, and is not complete enough for lossless mesh measurement. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method and device for determining lossless compression of a three-dimensional grid. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] The present invention provides a three-dimensional grid lossless compression determination method, comprising:

[0006] Performing a priori comparison between the to-be-matched mesh and the comparison mesh to determine whether the a priori comparison results of the to-be-matched mesh and the comparison mesh are consistent; if not, the two meshes do not match;

[0007] If they are consistent, the connection relationship between the to-be-matched grid and the comparison grid is compared to determine the matching result of the two grids.

[0008] The present invention also provides a three-dimensional grid lossless compression determination device, comprising:

[0009] The prior comparison module is used to perform a prior comparison between the to-be-matched mesh and the comparison mesh, and output a mesh mismatch result when the a prior comparison results between the to-be-matched mesh and the comparison mesh are inconsistent;

[0010] A connection relationship comparison module is used to compare the connection relationship between the to-be-matched mesh and the comparison mesh when the prior comparison results of the to-be-matched mesh and the comparison mesh are consistent, so as to determine the matching result of the two meshes, wherein the connection relationship includes at least one of a geometric coordinate connection relationship and a texture coordinate connection relationship.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] The three-dimensional grid lossless compression determination method of the present invention adds the determination of grid connection relationship, improves the determination of grid connection relationship in lossless measurement, and ensures the completeness of lossless grid measurement.

[0013] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of a three-dimensional mesh lossless compression determination method provided by an embodiment of the present invention;

[0015] Figure 2 is a schematic diagram of a TFAN triangle fan provided by an embodiment of the present invention;

[0016] Figure 3 is a schematic diagram of an Edgebreaker mode provided by an embodiment of the present invention;

[0017] Figure 4 It is a structural schematic diagram of a three-dimensional grid lossless compression determination device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a three-dimensional grid lossless compression determination method and device proposed by the present invention are described in detail below in combination with the accompanying drawings and specific implementation methods.

[0019] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0020] In the first aspect, the embodiment of the present invention proposes a method for determining lossless compression of a three-dimensional grid, see Figure 1 The schematic diagram of the method for determining lossless compression of a three-dimensional mesh is shown in FIG. The method for determining lossless compression of a three-dimensional mesh in this embodiment comprises the following steps:

[0021] Step 1: Perform a priori comparison between the grid to be matched and the comparison grid to determine whether the a priori comparison results of the grid to be matched and the comparison grid are consistent;

[0022] Step 2: If they are inconsistent, the two grids do not match; if they are consistent, the connection relationship between the grid to be matched and the comparison grid is compared to determine the matching result of the two grids.

[0023] In an optional embodiment, the prior comparison includes but is not limited to: texture map comparison, vertex number comparison, texture coordinate number comparison, and maximum number of adjacent triangles of the two meshes. When all prior comparisons of the two meshes are consistent, the connection relationship of the two meshes is further compared.

[0024] In an optional embodiment of the present invention, comparing the connection relationship between the to-be-matched grid and the comparison grid includes:

[0025] If the geometric coordinates and texture coordinates of the mesh share a set of connection relationships, then any one of the geometric coordinate connection relationships and texture coordinate connection relationships is compared; if the geometric coordinate connection relationship or the texture coordinate connection relationship of the mesh to be matched and the comparison mesh is consistent, the two meshes match, otherwise the two meshes do not match.

[0026] If the geometric coordinates and texture coordinates of the mesh have different connection relationships, the geometric coordinate connection relationship and the texture coordinate connection relationship are compared respectively. If the geometric coordinate connection relationship and the texture coordinate connection relationship of the to-be-matched mesh and the comparison mesh are consistent, the two meshes match, otherwise the two meshes do not match.

[0027] In this embodiment, the comparison process of the geometric coordinate connection relationship and the texture coordinate connection relationship is similar, so the comparison of the geometric coordinate connection relationship and the texture coordinate connection relationship includes:

[0028] For the first mesh vertex of the mesh to be matched, the unmatched second mesh vertices of the comparison mesh are traversed, and the parameter information of the first mesh vertex is compared with the parameter information of the second mesh vertex, until all the mesh vertices and triangles of the mesh to be matched are traversed, and the connection relationship comparison result of the mesh to be matched and the comparison mesh is determined.

[0029] Wherein, during the traversal process, the mesh state information of the mesh to be matched is updated according to the matching result of the first mesh vertex.

[0030] Optionally, the mesh state information includes: the traversal status of triangles in the mesh, the traversal status of vertices in the mesh, the traversal order of vertices in the mesh, and the number of vertices that have been visited in the mesh.

[0031] In an optional embodiment of the present invention, until all mesh vertices and triangles of the to-be-matched mesh are traversed, determining the connection relationship comparison result between the to-be-matched mesh and the comparison mesh includes:

[0032] After the mesh vertices and triangles of the to-be-matched mesh are traversed, if the parameter information of the to-be-matched mesh is consistent with the parameter information of the comparison mesh, the connection relationship between the to-be-matched mesh and the comparison mesh is consistent; otherwise, the connection relationship between the to-be-matched mesh and the comparison mesh is inconsistent.

[0033] In this embodiment, for the comparison of geometric coordinate connection relationships, the parameter information includes the geometric coordinates of the mesh vertices and the geometric coordinate connection relationships of the meshes represented by preset traversal rules; for the comparison of texture coordinate connection relationships, the parameter information includes the texture coordinates of the mesh vertices and the texture coordinate connection relationships of the meshes represented by preset traversal rules.

[0034] Optionally, the connection relationship of the mesh may be represented by a 3D mesh compression algorithm, such as the TFAN algorithm or the Edgebreaker algorithm or other mesh compression algorithms.

[0035] Furthermore, taking the comparison of the connection relationship of the geometric coordinates of the grid as an example, the comparison process using the TFAN algorithm is exemplified.

[0036] First, let's briefly introduce the TFAN algorithm. TFAN is the 3D mesh compression algorithm with the highest compression efficiency in the international standard SC3DMC. It encodes the connection relationship of 3D meshes in units of triangle sectors; it encodes the coordinates and attributes of points (including normal vectors, texture coordinates, vertex colors) using quantization, prediction, and entropy coding methods. TFAN can encode any mesh structure and can compress the connection relationship losslessly. However, when TFAN encodes the coordinates and attributes of points, quantization is a necessary module, so TFAN only supports lossy compression of point coordinates and attributes.

[0037] The algorithm defines a grid structure called a triangle fan (TF), such as Figure 2 As shown in the figure, all triangles in TF have a common vertex v7, which is the center of TF; every two consecutive triangles in TF share a common edge; all triangles in TF have the same direction, which refers to the direction of vertex traversal in the triangle.

[0038] The TFAN algorithm divides the 3D mesh into a cluster of TFs and defines 10 TF modes, using the mode to represent the traversal order of the TF. Because the TF already contains the connection relationship of the vertices in a TF, the codec can traverse the center point of the TFAN in the same order to obtain the vertex traversal order of the entire Mesh, and it can ensure that the codec obtains the same vertex traversal order. TFAN only needs to encode the mode number on demand to represent the connection relationship of the entire mesh. The connection relationship driven encoding method adopted by TFAN will follow the encoding order of the connection information for the encoding of geometric information and UV coordinates. In the process of encoding the geometric coordinates and UV coordinates, parallelogram prediction and similar triangle prediction are performed on the geometric coordinates and UV coordinates respectively according to the vertex order encoded by the connection relationship, and the prediction residual is entropy encoded.

[0039] In an optional embodiment, the specific process of using the TFAN algorithm to compare the geometric coordinate connection relationship of the grids is as follows: For the convenience of description, the grid to be matched is recorded as grid A, and the comparison grid is recorded as grid B.

[0040] a: construct the first TFAN with any first mesh vertex in mesh A as the center point, and update the state information of mesh A.

[0041] b: Find whether there is a point in mesh B that matches the first mesh vertex of mesh A. If the geometric coordinates of the second mesh vertex in mesh B and the second TFAN constructed with the second mesh vertex as the center point are consistent with the first mesh vertex and the first TFAN of mesh A, then the second mesh vertex is considered to be a matching point with the first mesh vertex;

[0042] c: For each first mesh vertex in mesh A, traverse the unmatched second mesh vertices in mesh B to obtain the matching point situation of each first mesh vertex in mesh A. The matching point situation of the first mesh vertex includes the following three situations: 0 represents no matching point; 1 represents 1 matching point; and greater than 1 represents multiple matching points.

[0043] During the traversal process, if there is a matching point in mesh B, the matching point is selected as the matching mesh point of the first mesh vertex; if there are multiple matching points in mesh B, a matching point is randomly selected as the matching mesh point of the first mesh vertex, and the remaining matching points are saved as candidate matching mesh points of the first mesh vertex.

[0044] If there is no matching point in mesh B, the matching mesh point of the previous first mesh vertex is changed. The specific changing process is: if there is an alternative matching mesh point for the previous first mesh vertex, a random alternative matching mesh point is selected as the matching mesh point of the first mesh vertex, and the matching mesh point before the change is used as the unmatched second mesh vertex; if there is no alternative matching mesh point for the previous first mesh vertex, it is considered that the first mesh vertex has no matching point in mesh B.

[0045] d: Until all mesh vertices and triangles of mesh A are traversed, if the first mesh vertex of mesh A has a matching mesh point in mesh B, the geometric connection relationship between mesh A and mesh B is consistent; otherwise, the geometric connection relationship between mesh A and mesh B is inconsistent.

[0046] It should be noted that, for the initial first mesh vertex in mesh A, if no matching point is found in mesh B, it is considered that the geometric coordinate connection relationship between mesh A and mesh B is inconsistent.

[0047] Furthermore, for the first mesh vertex of mesh A, the process of how to find a point matching it in mesh B is described in detail.

[0048] First, for the first mesh vertex of mesh A, the first TFAN is constructed with the first mesh vertex as the center point (it should be noted that there is a non-manifold structure so that there may be multiple TFANs constructed at this point), and the state information of the TFAN (including: 1. TFAN mode, 2. TFAN degree, 3. point traversal information, 4. point relative index information, 5. mesh vertex traversal order) is saved, and the starting face and the next face (used to determine the order of TFAN) for constructing the first TFAN of the first mesh point are saved.

[0049] Then, loop through the unmatched second mesh vertex in mesh B and compare the geometric coordinates of the two mesh vertices. If the geometric coordinates are the same, compare whether the TFANs constructed based on the two mesh vertices are the same. If they are the same, the two mesh vertices match; otherwise, the two mesh vertices are considered to be unmatched.

[0050] In this embodiment, the comparison of TFAN specifically includes: transmitting the information of the starting face and the next face of the first TFAN constructed by the first mesh vertex to mesh B, and the second mesh vertex of mesh B constructs the second TFAN according to the information, and respectively compares the five state information of the first TFAN and the second TFAN. If the five state information are all the same, it is considered that the second TFAN is consistent with the first TFAN, otherwise, it is considered that the two TFANs are inconsistent.

[0051] It is worth noting that when constructing the second TFAN at the second mesh vertex of mesh B, multiple faces stacked together may result in multiple second TFANs being constructed, and the first TFAN needs to be compared with each second TFAN to confirm whether they are consistent. When constructing multiple first TFANs with the first mesh vertex as the center point, the information of the starting face and the next face of each first TFAN needs to be transferred to mesh B, so that the second mesh vertex of mesh B constructs the corresponding second TFAN according to the corresponding information. For each first TFAN, there is a second TFAN that is consistent with it, and it is considered that the first TFAN constructed with the first mesh vertex as the center is consistent with the second TFAN constructed with the second mesh vertex as the center.

[0052] The process of comparing the connection relationship of the texture coordinates of the mesh using the TFAN algorithm is similar to the process of comparing the connection relationship of the geometric coordinates, which will not be described here.

[0053] Furthermore, taking the comparison of the connection relationship of the geometric coordinates of the mesh as an example, the comparison process using the Edgebreaker algorithm is exemplified.

[0054] First, the Edgebreaker algorithm is briefly introduced. The Edgebreaker algorithm is a three-dimensional mesh connection relationship encoding method with the advantages of good compression performance, easy implementation, and the ability to provide an upper limit on the compression ratio. The Edgebreaker method itself only describes the compression method of the three-dimensional mesh connection information. The three-dimensional mesh can only be compressed through geometric information compression and entropy coding.

[0055] The Edgebreaker encoding algorithm uses five different modes (called C, L, E, R, and S) to represent the connectivity of a 3D mesh. During the encoding process, each triangle of the mesh is accessed in depth-first order, and each triangle is marked according to the mode it is in, generating a CLERS string to obtain a compact representation of the connectivity of the mesh.

[0056] See also Figure 3 The Edgebreaker mode diagram shows the five modes of the Edgebreaker method. Figure 3As shown. The three-dimensional mesh is divided into a traversed part and an untraversed part, and the boundary between the two parts is called the active boundary. In the Edgebreaker encoding process, the triangle to be traversed is accessed by traversing the active edges on the active boundary, and the mode to be used is selected according to the relationship between the active edge and the triangle in which it is located. Specifically, if the third vertex connected to the active edge in the triangle is not on the active boundary, the current triangle is marked as C mode; if the third vertex is on the active boundary and is the next vertex of the current active edge vertex in counterclockwise order, the current triangle is marked as R mode; if the third vertex is on the active boundary and is the previous vertex of the current active edge vertex in counterclockwise order, the current triangle is marked as L mode; if the third vertex is on the active boundary and is both the previous vertex of the current active edge vertex and the next vertex of the current active edge in counterclockwise order, the current triangle is marked as E mode; if the third vertex is on the active boundary, but is neither the previous vertex of the current active edge vertex nor the next vertex of the current active edge in counterclockwise order, the current triangle is marked as S mode.

[0057] After marking a triangle each time, the active boundary is updated and the next active edge is selected according to certain rules. After traversing all triangles, the corresponding CLERS string is entropy encoded to obtain higher compression efficiency.

[0058] In an optional embodiment, the specific process of using the Edgebreaker algorithm to compare the geometric coordinate connection relationship of the meshes is as follows: For the convenience of description, the mesh to be matched is recorded as mesh A, and the comparison mesh is recorded as mesh B.

[0059] Select the initial triangle in mesh A, determine its mode type according to the vertex traversal, and update the state information of mesh A. Find the triangle with geometric coordinates in mesh B, and compare the mode type of the corresponding triangle; through the traversal rules of Edgebreaker, traverse all the untraversed triangles in the mesh in turn and obtain the mode string representing the connection relationship. By comparing the mode strings of mesh A and mesh B, as well as the geometric coordinates of the corresponding vertices of the triangle, when the geometric coordinates and the mode string are consistent, it is considered that the connection relationship of the two meshes is consistent; otherwise, it is considered that the connection relationship of the two meshes is inconsistent.

[0060] The process of comparing the texture coordinate connection relationship of the mesh using the Edgebreaker algorithm is similar to the process of comparing the geometric coordinate connection relationship, which will not be described here.

[0061] The three-dimensional mesh lossless compression determination method of the embodiment of the present invention adds the determination of mesh connection relationship to the lossless mesh compression detection, solves the problem of missing the determination of mesh connection relationship in the lossless mesh compression detection measurement, improves the determination of mesh connection relationship in the lossless measurement, and ensures the completeness of the lossless mesh measurement. Moreover, it also solves the problem when the geometry and texture have two sets of connection relationships when determining the lossless compression of the three-dimensional mesh.

[0062] In the second aspect, corresponding to the three-dimensional mesh lossless compression determination method proposed in the first aspect, an embodiment of the present invention proposes a three-dimensional mesh lossless compression determination device, see Figure 4 , the dimensional grid lossless compression determination device comprises:

[0063] The prior comparison module 100 is used to perform a prior comparison between the to-be-matched mesh and the comparison mesh, and output a mesh mismatch result when the prior comparison results between the to-be-matched mesh and the comparison mesh are inconsistent;

[0064] The connection relationship comparison module 200 is used to compare the connection relationship between the to-be-matched mesh and the comparison mesh when the prior comparison results of the to-be-matched mesh and the comparison mesh are consistent, and determine the matching result of the two meshes, wherein the connection relationship includes at least one of a geometric coordinate connection relationship and a texture coordinate connection relationship.

[0065] For the specific contents of the three-dimensional mesh lossless compression determination device and the corresponding beneficial effects, please refer to the relevant contents of the three-dimensional mesh lossless compression determination method provided in the first aspect, which will not be elaborated here.

[0066] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of further restrictions, the elements defined by the statement "including one..." do not exclude the existence of other identical elements in the article or device including the elements. Similar words such as "connect" or "connected" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0067] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for determining lossless compression of a three-dimensional mesh, characterized in that: include: Performing a priori comparison between the to-be-matched mesh and the comparison mesh to determine whether the a priori comparison results of the to-be-matched mesh and the comparison mesh are consistent; if not, the two meshes do not match; If they are consistent, the connection relationship between the to-be-matched grid and the comparison grid is compared to determine the matching result of the two grids.

2. The three-dimensional mesh lossless compression determination method according to claim 1, characterized in that: The a priori comparison includes: comparison of texture maps of two meshes, comparison of vertex numbers, comparison of texture coordinate numbers, and comparison of maximum numbers of adjacent triangles of vertices.

3. The three-dimensional mesh lossless compression determination method according to claim 1, characterized in that: The connection relationship includes at least one of a geometric coordinate connection relationship and a texture coordinate connection relationship.

4. The three-dimensional mesh lossless compression determination method according to claim 3, characterized in that: Comparing the connection relationship between the to-be-matched grid and the comparison grid includes: If the geometric coordinates and texture coordinates of the mesh share a set of connection relationships, then any one of the geometric coordinate connection relationships and the texture coordinate connection relationships is compared; if the geometric coordinate connection relationship or the texture coordinate connection relationship of the mesh to be matched and the comparison mesh is consistent, then the two meshes match, otherwise the two meshes do not match; If the geometric coordinates and texture coordinates of the mesh have different connection relationships, the geometric coordinate connection relationship and the texture coordinate connection relationship are compared respectively. If the geometric coordinate connection relationship and the texture coordinate connection relationship of the mesh to be matched and the comparison mesh are consistent, the two meshes match, otherwise the two meshes do not match.

5. The three-dimensional mesh lossless compression determination method according to claim 4, characterized in that: Comparing any one of the geometric coordinate connection relationship and the texture coordinate connection relationship, including: For the first mesh vertex of the mesh to be matched, traverse the unmatched second mesh vertex of the comparison mesh, compare the parameter information of the first mesh vertex with the parameter information of the second mesh vertex, until all the mesh vertices and triangles of the mesh to be matched are traversed, and determine the comparison result of the connection relationship between the mesh to be matched and the comparison mesh; Wherein, during the traversal process, the mesh state information of the to-be-matched mesh is updated according to the matching result of the first mesh vertex.

6. The three-dimensional mesh lossless compression determination method according to claim 5, characterized in that: The mesh state information includes: the traversal status of triangles in the mesh, the traversal status of vertices in the mesh, the traversal order of vertices in the mesh and the number of vertices that have been visited in the mesh.

7. The three-dimensional mesh lossless compression determination method according to claim 5, characterized in that: Until all mesh vertices and triangles of the to-be-matched mesh are traversed, a comparison result of the connection relationship between the to-be-matched mesh and the comparison mesh is determined, including: When all mesh vertices and triangles of the mesh to be matched are traversed, if the parameter information of the mesh to be matched is consistent with the parameter information of the comparison mesh, then the connection relationship between the mesh to be matched and the comparison mesh is consistent; Otherwise, the connection relationship between the to-be-matched grid and the comparison grid is inconsistent.

8. The three-dimensional mesh lossless compression determination method according to claim 7, characterized in that: For the comparison of the geometric coordinate connection relationship, the parameter information includes the geometric coordinates of the mesh vertices and the geometric coordinate connection relationship of the mesh represented by a preset traversal rule; For the comparison of the texture coordinate connection relationship, the parameter information includes the texture coordinates of the mesh vertices and the texture coordinate connection relationship of the mesh represented by a preset traversal rule.

9. A three-dimensional grid lossless compression determination device, characterized in that: include: The prior comparison module is used to perform a priori comparison between the to-be-matched mesh and the comparison mesh, and output a mesh mismatch result when the a priori comparison results between the to-be-matched mesh and the comparison mesh are inconsistent; A connection relationship comparison module is used to compare the connection relationship between the to-be-matched mesh and the comparison mesh when the prior comparison results of the to-be-matched mesh and the comparison mesh are consistent, so as to determine the matching result of the two meshes, wherein the connection relationship includes at least one of a geometric coordinate connection relationship and a texture coordinate connection relationship.

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