阅读说明：本技术 一种基于邻近点投影分布特征的点云快速投影方法 (Point cloud rapid projection method based on adjacent point projection distribution characteristics ) 是由 王军 方猛 于 2020-04-30 设计创作，主要内容包括：本发明提出一种基于邻近点投影分布特征的点云快速投影方法,包括以下步骤：将点云划分为固定大小的网格；计算首个网格对应的邻近网格的全零列索引final；根据所述全零列索引final,计算当前网格对应的邻近网格中全零列索引final对应的平面以外的平面的scoreSmooth累加值,然后计算当前网格中每个平面的scoreSmooth累加值及当前网格的scoreNromal值的加权和,取所述加权和数值最大时对应的平面作为当前网格的投影平面；计算次个网格对应的邻近网格的全零列索引final,并重复上述步骤至所有网格完成遍历,得到点云中每个点的投影情况。(The invention provides a point cloud rapid projection method based on adjacent point projection distribution characteristics, which comprises the following steps: dividing the point cloud into grids with fixed sizes; calculating all zero column index final of the adjacent grid corresponding to the first grid; according to the all-zero-column index final, calculating the scoreSimoth accumulated value of the plane except the plane corresponding to the all-zero-column index final in the adjacent grid corresponding to the current grid, then calculating the weighted sum of the scoreSimoth accumulated value of each plane in the current grid and the scoreMale value of the current grid, and taking the plane corresponding to the maximum value of the weighted sum as the projection plane of the current grid; and calculating the all-zero-column index final of the adjacent grid corresponding to the next grid, and repeating the steps until all grids are traversed to obtain the projection condition of each point in the point cloud.)

1. A point cloud fast projection method based on adjacent point projection distribution characteristics is characterized by comprising the following steps:

s1: dividing the point cloud into grids with fixed sizes;

s2: calculating all zero column indexes final of all adjacent grids of the first grid; wherein, the full zero column index final is a character string formed by plane indexes which are not projected in the adjacent grid corresponding to the current grid;

s3: according to the all-zero-column index final, calculating the scoreSimoth accumulated value of the plane except the plane corresponding to the all-zero-column index final in the adjacent grid corresponding to the current grid, then calculating the weighted sum of the scoreSimoth accumulated value of each plane in the current grid and the scoreNormal value of the current grid, and taking the plane corresponding to the maximum value of the weighted sum as the projection plane of the current grid;

s4: and calculating all zero column indexes final of the adjacent grids corresponding to the secondary grid, skipping to execute the step S3, and repeating the step until all grids are traversed to obtain the projection plane of each point in the point cloud.

2. The point cloud fast projection method of claim 1, wherein: in the step S2, the specific step of calculating all zero-column indices final of all neighboring grids of the current grid is as follows:

s2.1: acquiring scoreSimoth values of six planes of a first adjacent grid of a current grid, storing the scoreSimoth values in a temporary character string variable temp, and assigning the value of the temporary character string variable temp to a full zero-column index final character string;

s2.2: clearing the temporary character string variable temp, obtaining scoreSimoth values of six planes of a next adjacent grid of the current grid, and storing the scoreSimoth values in the temporary character string variable temp;

s2.3: performing AND operation on the values of the temporary character string variable temp and the all-zero-column index final, reserving the same characters and storing the same characters in the all-zero-column index final;

s2.4: and repeating the steps S2.2-S2.4 until the adjacent grids of the current grid are traversed to obtain the all-zero-column index final of all the adjacent grids of the current grid.

3. The point cloud fast projection method of claim 2, wherein: the next adjacent grid processed in the step S2.2 is separated from the adjacent grid processed in the previous step by n adjacent grids, where n is a positive integer.

4. The point cloud fast projection method of claim 3, wherein: and the value range of the number n of the adjacent grids which are separated from the successively traversed adjacent grids is 5-20.

5. The point cloud fast projection method of claim 1, wherein: the number of neighboring grids is determined by the search radius of the point cloud and the size of the grid.

6. The point cloud fast projection method of claim 1, wherein: in the step S3, the scoreNromal value of the current mesh is obtained by performing inner product operation on the normal vector of the point cloud corresponding to the current mesh and the normal vector of each plane of the point cloud.

Technical Field

The invention relates to the technical field of point cloud coding, in particular to a point cloud rapid projection method based on adjacent point projection distribution characteristics.

Background

V-PCC (Video-based Point Cloud Compression) is the standard for Point Cloud Compression coding currently being established by MPEG. In the encoding process of the current reference software TMC2 of V-PCC (Video-based Point cloud compression), the process of generating patch mainly includes three steps: initial partitioning, improved partitioning, and patch generation, where the functions of the initial partitioning and improved partitioning process are used to determine on which plane of the bounding box hexahedron each point in the point cloud is projected.

However, in the improved partitioning process of point cloud compression, by partitioning the point cloud into grids, a neighboring grid search is performed for each grid, and for all neighboring grids, the cumulative sum of the scoremooth values of six planes thereof needs to be calculated, which takes a lot of time. Furthermore, in the case of projection in the neighboring mesh of each point in the point cloud, there may be a case where the points in all neighboring meshes of a point are generally projected on only some planes of six planes, and sometimes all of them are projected on only one plane. As shown in fig. 1, the projection condition of the points of the partial adjacent grids is shown, wherein each line number represents the condition that the points in each grid are projected to six planes, and each value represents the number of the points projected to the plane in the current grid. It can be seen that if six planes are traversed in the original program, a large amount of unnecessary computation is generated, because if some planes are not projected, for example, the kth plane is not projected, the values of scoremooth [ k ] are many cases of 0 being accumulated, and although the improved partitioning process is to traverse each mesh, the data amount is still huge, so that the problem of unnecessary computation is generated in the improved partitioning process of point cloud compression.

Disclosure of Invention

The invention provides a point cloud rapid projection method based on adjacent point projection distribution characteristics, aiming at overcoming the defect of large unnecessary calculation amount in the improved partitioning process of point cloud compression in the prior art.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a point cloud fast projection method based on adjacent point projection distribution characteristics comprises the following steps:

s1: dividing the point cloud into grids with fixed sizes;

s2: calculating all zero column indexes final of all adjacent grids of the first grid; wherein, the full zero column index final is a character string formed by plane indexes which are not projected in the adjacent grid corresponding to the current grid;

s3: according to the all-zero-column index final, calculating the scoreSimoth accumulated value of the plane except the plane corresponding to the all-zero-column index final in the adjacent grid corresponding to the current grid, then calculating the weighted sum of the scoreSimoth accumulated value of each plane in the current grid and the scoreNormal value of the current grid, and taking the plane corresponding to the maximum value of the weighted sum as the projection plane of the current grid; the scoremooth value is an inherent attribute of each grid and is used for reflecting the projection condition of the current grid;

s4: and calculating all zero column indexes final of the adjacent grids corresponding to the secondary grid, skipping to execute the step S3, and repeating the step until all grids are traversed to obtain the projection plane of each point in the point cloud.

The technical scheme improves the improved dividing step in the process of generating the patch in the V-PCC. The improved partitioning step in the technical scheme is carried out on the basis of grids, the point cloud is partitioned to obtain grids with fixed sizes, wherein the grids are of similar cube structures and comprise six projectable planes; before traversing the adjacent grids corresponding to the current grid, firstly, counting the plane indexes which are not projected by all the adjacent grids corresponding to the current grid to obtain the all-zero-column index final of the current grid, then, performing improved division by taking the all-zero-column index final as a judgment condition, calculating the scoreSimoth values of all planes except the plane corresponding to the plane index in the all-zero-column index final character string, namely calculating the scoreSimoth value of the plane with the projection of the adjacent grid, then calculating the weighted sum of the scoreSimoth value of each plane and the scoreMaral value of the current grid, and taking the plane corresponding to the maximum weighted sum value as the projection plane of the point of the current grid, namely, completing the determination of the projection plane of the current grid. The technical scheme can reduce the scoreSimoth value of a plane without projection, thereby reducing a large amount of unnecessary calculation.

Preferably, in the step S2, the specific step of calculating all zero column indexes final of all neighboring grids of the current grid is as follows:

s2.1: acquiring a scoreSimoth value of a first adjacent grid of a current grid, storing the scoreSimoth value in a temporary character string variable temp, and assigning the value of the temporary character string variable temp to a full zero-column index final character string;

s2.2: clearing the temporary character string variable temp, obtaining scoreSimoth values of six planes of a next adjacent grid of the current grid, and storing the scoreSimoth values in the temporary character string variable temp;

s2.3: performing AND operation on the values of the temporary character string variable temp and the all-zero-column index final, reserving the same characters of the temporary character string variable temp and the all-zero-column index final, and storing the same characters in the all-zero-column index final;

s2.4: and repeating the steps S2.2-S2.4 until the adjacent grids of the current grid are traversed, and obtaining the all-zero-column index final of all the adjacent grids of the current grid.

Preferably, the next adjacent grid processed in the step S2.2 is separated from the adjacent grid processed in the previous step by n adjacent grids, where n is a positive integer. The optimal scheme processes the adjacent grids at intervals of a certain number, and can further reduce unnecessary calculation amount in the process of improving the division while ensuring the accuracy of determining the projection plane of the current grid.

Preferably, the value range of the number n of adjacent grids spaced between the successively traversed adjacent grids is 5-20.

Preferably, the number of neighboring meshes is determined by the search radius of the point cloud and the size of the mesh.

Preferably, in the step S3, the scorennormal value of the current mesh is obtained by performing an inner product operation on the normal vector of the point cloud corresponding to the current mesh and the normal vector of each plane of the point cloud.

Compared with the prior art, the technical scheme of the invention has the beneficial effects that: by counting all planes which are not projected by adjacent grids of the current grid in advance and then skipping the scoreSimoth accumulated value of the projection-free plane obtained by calculation and statistics in the process of executing improved partitioning, unnecessary calculation is avoided, the calculation amount in the improved partitioning process of point cloud compression is effectively reduced, and the running time in the point cloud encoding process is reduced.

Drawings

Fig. 1 is a schematic diagram of a projection of a portion of points adjacent to a grid.

Fig. 2 is a flowchart of a point cloud fast projection method based on a projection distribution feature of neighboring points according to this embodiment.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent;

it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

The present embodiment provides a point cloud fast projection method based on neighboring point projection distribution features, as shown in fig. 2, which is a flowchart of the point cloud fast projection method based on neighboring point projection distribution features of the present embodiment.

The point cloud fast projection method based on the projection distribution characteristics of the neighboring points provided by the embodiment comprises the following steps:

s1: the point cloud is divided into fixed size grids.

S2: calculating all zero column indexes final of all adjacent grids of the first grid; and the all-zero-column index final is a character string formed by plane indexes which are not projected in the adjacent grid corresponding to the current grid.

In this step, the all-zero column index final is obtained by judging which plane has a scoreSmooth [ k ] value of 0 in six planes of 0, 1, 2, 3, 4 and 5 in the current grid; the specific steps of calculating all zero column indexes final of all adjacent grids of the current grid are as follows:

s2.1: acquiring scoreSimoth values of six planes of a first adjacent grid of a current grid, storing the scoreSimoth values in a temporary character string variable temp, and assigning the value of the temporary character string variable temp to a full zero-column index final character string;

s2.2: clearing the temporary character string variable temp, obtaining scoreSimoth values of six planes of a next adjacent grid of the current grid, and storing the scoreSimoth values in the temporary character string variable temp;

s2.3: performing AND operation on the values of the temporary character string variable temp and the all-zero-column index final, reserving the same characters of the temporary character string variable temp and the all-zero-column index final, and storing the same characters in the all-zero-column index final;

s2.4: and repeating the steps S2.2-S2.4 until the adjacent grids of the current grid are traversed, and obtaining the all-zero-column index final of all the adjacent grids of the current grid.

In this embodiment, the next adjacent grid processed in step S2.2 is separated from the adjacent grid processed in the previous step by 20 adjacent grids.

S3: and calculating the scoreSimoth accumulated value of the planes except the plane corresponding to the all-zero column index final in the adjacent grid corresponding to the current grid according to the all-zero column index final, then calculating the weighted sum of the scoreSimoth accumulated value of each plane in the current grid and the scoreMormal value of the current grid, and taking the plane corresponding to the maximum value of the weighted sum as the projection plane of the current grid. The scoreSimoth value is an inherent attribute of each grid and is used for reflecting the projection condition of the current grid, and the scoreMicromal value is obtained by performing inner product operation on a normal vector of a point cloud corresponding to the current grid and a normal vector of each plane of the point cloud.

S4: and calculating all zero column indexes final of the adjacent grids corresponding to the secondary grid, skipping to execute the step S3, and repeating the step until all grids are traversed to obtain the projection plane of each point in the point cloud.

In a specific implementation process, the point cloud is divided into grids with fixed sizes according to grid sizes preset by a user, and the grid traversal is performed by traversing the content of the adjacent grid part in a redefinition grid based function in a TMC2 encoder.

Defining an all-zero-column index string variable final for storing plane indexes of all adjacent grids of the current grid without projection; a temporary string variable temp is defined for temporarily storing the plane indices of the current neighboring grid that have not been projected.

Acquiring an adjacent grid list adj of the current grid, defining an iterator for traversing the adjacent grid of the current grid, and setting a pointing interval of the iterator to be 20 elements, namely indicating that 20 adjacent grids are separated for traversal processing.

The iterator traverses from the first element in the neighboring mesh list adj, i.e. starts processing from the first neighboring mesh of the current mesh: judging six scoreSimoth [ k ] values of the adjacent grids pointed by the iterator, wherein k represents a plane index, and the values of k are 0, 1, 2, 3, 4 and 5, which respectively represent a first plane to a sixth plane; if the value of scoremooth [ k ] is 0, it indicates that the plane with the plane index k is not projected, for example, when scoremooth [0] ═ 3, scoremooth [1] ═ 0, scoremooth [2] ═ 3, scoremooth [3] ═ 0, scoremooth [4] ═ 0, and scoremooth [5] ═ 0, then the first plane and the third plane in the currently traversed adjacent grid are projection planes, and the other planes are projection-free planes, then the temporary string variable temp is assigned to "1345", and the all-zero-column index string variable final is assigned to "1345", and the temporary string variable temp is cleared.

Then the iterator points to the 21 st element, i.e. skips 20 adjacent grids to go through, and then assigns a value to the temporary string variable temp according to six scoresmooh [ k ] values in the adjacent grids pointed by the iterator, to obtain an index of no projection plane in the adjacent grids, for example, the scoresmooh [ k ] in the adjacent grids is: the scoreSmooth [0] ═ 0, scoreSmooth [1] ═ 4, scoreSmooth [2] ═ 3, scoreSmooth [3] ═ 0, scoreSmooth [4] ═ 2, and scoreSmooth [5] ═ 0, that is, the first plane, the fourth plane, and the sixth plane in the currently traversed adjacent grid are projection-free planes, at this time, the temporary string variable temp is assigned to "035", and then the temporary string variable temp ═ 035 "is and-operated with the all-zero-column index string variable final ═ 1345", so as to obtain the all-zero-column index string variable final ═ 35 ", and the temporary string variable temp is cleared.

And repeating the steps until the iterator finishes traversing the adjacent grid list adj, and accumulating the plane scoreSimoth [ k ] values of each adjacent grid in the adjacent grid list adj except the all-zero-column index character string variable final according to the finally obtained numerical value in the all-zero-column index character string variable final. For example, when the finally obtained all-zero-column index string variable final is "35", that is, it indicates that all neighboring grids have no projection on the fourth plane and the sixth plane, the accumulation calculation of scoremoth [3] and scoremoth [5] is skipped, only the accumulation calculation of scoremoth [0], scoremoth [1], scoremoth [2] and scoremoth [4] of each neighboring grid is performed, so as to obtain a scoremoth accumulated value, and then the weighted sum of the scoremoth accumulated value of each plane and the scoremonal value of the current grid is calculated, and the plane corresponding to the maximum weighted sum is taken as the projection plane of the current grid.

And repeatedly executing the steps to complete the traversal of all the grids, obtaining the projection plane of each point in the point cloud, and applying the projection plane to the patch generation step.

According to the method, all planes which are not projected by adjacent grids of the current query grid are counted in advance, and then the scoreSimoth accumulated value of the projection-free planes obtained by calculation and statistics is skipped in the process of executing improved partitioning, so that unnecessary calculation is avoided, the calculation amount in the process of improving partitioning of point cloud compression is effectively reduced, and the running time in the process of point cloud encoding is reduced.

In this embodiment, taking a root sequence as an example, through experimental statistics, 2 planes among six projection planes are projection-free planes for all points in the neighboring grid list of each current query grid, and after the point cloud fast projection method based on the neighboring point projection distribution feature provided by this embodiment is adopted, the computation time of 1/3 can be reduced in the process of traversing the grids, and the running time of the process of traversing the grids accounts for about 40% of the total encoding time, whereas the point cloud fast projection method based on the neighboring point projection distribution feature provided by this embodiment can reduce the running time of the total encoding process by 10%. The point cloud fast projection method based on the projection distribution characteristics of the neighboring points, which is provided by the embodiment, can also have the effect of reducing the encoding time to some extent for other sequences.

The terms describing positional relationships in the drawings are for illustrative purposes only and are not to be construed as limiting the patent;

it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.