A target infrared calculation method based on multi-resolution grid

Abstract

The present invention discloses a target infrared calculation method based on a multi-resolution grid, comprising: obtaining a first surface grid in a volume grid of a geometric model, establishing a first mapping from a second surface grid to the first surface grid, establishing a second mapping from a texture map of the geometric model to a third surface grid, obtaining the temperature of each pixel in the texture map according to the first mapping and the second mapping, voxelizing the volume grid, performing ray tracing based on the multi-resolution grid, calculating the solid infrared radiation brightness of the target area of ​​the geometric model, and calculating the gas infrared radiation brightness of the target area of ​​the geometric model based on ray tracing. The present invention simplifies the complexity of infrared radiation brightness calculation in the volume grid by voxelizing the volume grid of the geometric model, switching surface grids of different resolutions according to distance, so that the target heat based on the texture map calculated on one surface grid can be mapped to the surface grids of multiple resolutions, thereby improving the efficiency of ray tracing.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared radiation calculation, and in particular relates to a target infrared calculation method based on multi-resolution grids. Background Art

[0002] The volume mesh structure of the target geometric model is relatively complex. In the prior art solutions, unstructured meshes are usually used directly for ray tracing. However, ray tracing of the target's unstructured mesh is relatively complex and inefficient.

[0003] In order to improve the efficiency of ray tracing, it is necessary to map the unstructured grid of the target geometric model to the structured grid describing the flow field around the target geometric model and the surface grid describing the surface of the target geometric model. For the structured grid describing the flow field around the target, it is easier to achieve mapping between multi-resolution grids. For the surface grid describing the surface of the model, it is necessary to design multi-resolution surface grids and calculate the target heat of surface grids of different resolutions respectively. This makes it difficult to improve the efficiency of ray tracing of the target geometric model, greatly reducing the efficiency of the target infrared radiation calculation. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a target infrared calculation method based on a multi-resolution grid, and the target infrared calculation method comprises:

[0005] Step 1: obtaining a first surface mesh in a volume mesh of a geometric model, wherein the volume mesh is pre-set with a temperature value and a gas concentration value of the geometric model, and in the first surface mesh, the same face element corresponding to the volume mesh includes a corresponding temperature value;

[0006] Step 2: Establish a first mapping from a second surface mesh to the first surface mesh, wherein the second surface mesh has the geometric coordinates of the geometric model, and the second surface mesh and the first surface mesh have the same shape, size, coordinate axis direction, and main direction of the geometric model, and the first mapping is a corresponding relationship between the vertex coordinate projection of each face element in the second surface mesh and the face element of the first surface mesh;

[0007] Step 3, establishing a second mapping from the texture map of the geometric model to a third surface mesh, wherein the third surface mesh is a surface mesh having the texture coordinates of the geometric model generated by copying the second surface mesh, and the second mapping is a correspondence between the projection of the center point of each pixel in the texture map of the geometric model and the face element of the third surface mesh;

[0008] Step 4: Obtain the temperature of each pixel in the texture map according to the first mapping and the second mapping;

[0009] Step 5, voxelizing the volume grid into flow field;

[0010] Step 6: Perform ray tracing based on a multi-resolution grid to calculate the solid infrared radiation brightness of the target area of ​​the geometric model, and calculate the gas infrared radiation brightness of the target area of ​​the geometric model based on the ray tracing.

[0011] In one embodiment of the present invention, step 1, obtaining a first surface mesh in a volume mesh of a geometric model, includes generating a first surface mesh corresponding to the volume mesh according to a wall relationship and a point-surface relationship in a volume mesh pre-set for the geometric model, wherein the temperature value and the gas concentration value of the geometric model are pre-set in the volume mesh.

[0012] In one embodiment of the present invention, step 2, establishing a first mapping from the second surface mesh to the first surface mesh, comprises:

[0013] Step 2.1, generating a second surface mesh according to the obj file or gltf file of the geometric model, wherein the second surface mesh has the geometric coordinates of the geometric model, and the second surface mesh has the same shape, size, coordinate axis direction and main direction of the geometric model as the first surface mesh;

[0014] Step 2.2, dividing the first surface mesh into m*n*k first grid spaces, each first grid space corresponding to a different face element of the first surface mesh contained therein, wherein m, n and k are all positive integers greater than 0;

[0015] Step 2.3, converting the vertex coordinates of each face element in the second face mesh to the coordinate system of the first face mesh, and calculating the first mesh space corresponding to the vertex coordinates of each face element in the second face mesh in the coordinate system of the first face mesh;

[0016] Step 2.4: Obtain the corresponding relationship between the vertex coordinate projection of each face element in the second face mesh and the face element of the first face mesh.

[0017] In one embodiment of the present invention, step 2.3, converting the vertex coordinates of each facet in the second face mesh to the coordinate system of the first face mesh, comprises:

[0018] Converting the vertex coordinates of each face element in the second face mesh to an intermediate coordinate system, wherein the intermediate coordinate system is a coordinate system that keeps the coordinate axis direction of the second face mesh unchanged and takes the minimum coordinate point in the second face mesh as the coordinate origin;

[0019] The vertex coordinates of each face element in the second face mesh in the intermediate coordinate system are converted to the coordinate system of the first face mesh.

[0020] In one embodiment of the present invention, step 2.4, obtaining the correspondence between the vertex coordinate projection of each face element in the second face mesh and the face element of the first face mesh, includes:

[0021] According to the first grid space corresponding to the vertex coordinates of each face element in the second face mesh and different face elements of the first face mesh corresponding to the first grid space, projecting the vertex coordinates of each face element in the second face mesh to different face elements of the first face mesh corresponding to the corresponding first grid space;

[0022] When the vertex coordinates are projected into the face element in the first face mesh corresponding to the corresponding first mesh space, and the normal direction of the vertex is consistent with the normal direction of the face element in the corresponding first face mesh, the distance between the vertex and the face element in the first face mesh with the corresponding normal direction is calculated, and the correspondence between the face element of the first face mesh and the projection of the vertex coordinates when the distance is shortest is the first mapping.

[0023] In one embodiment of the present invention, step 3, establishing a second mapping of the texture map of the geometric model to the third surface mesh, comprises:

[0024] Step 3.1, copying the second surface mesh to a third surface mesh, and replacing the geometric coordinates of the vertices of each face element in the third surface mesh with the texture coordinates of the vertices;

[0025] Step 3.2, dividing the third surface mesh into p*q*1 third grid spaces, each third grid space corresponds to a different face element of the third surface mesh contained therein, wherein p and q are both positive integers greater than 0;

[0026] Step 3.3, obtain the texture map of the geometric model, calculate the third grid space corresponding to the center point of each pixel in the texture map, project the center point of each pixel to the face element in the corresponding third surface mesh in the corresponding third grid space, when the center point of the pixel is projected within the face element in the corresponding third surface mesh, the correspondence between the projection of the center point of the pixel and the face element in the corresponding third surface mesh is the second mapping.

[0027] In one embodiment of the present invention, step 4, obtaining the temperature of each pixel in the texture map according to the first mapping and the second mapping, comprises:

[0028] Step 4.1, according to the second mapping, obtain the face element M on the third face mesh corresponding to the projection of the center point of the pixel point N in the texture map, wherein N and M are both positive integers greater than or equal to 1;

[0029] Step 4.2: According to the face element M on the second face mesh and the first mapping, obtain the face element K of the first face mesh corresponding to the coordinate projection of the vertex i of the face element M. i , wherein i=1, 2, ..., F, F represents the number of vertices of the face element M, and i represents the vertex i of the face element M;

[0030] Step 4.3: Based on the surface element K of the first surface mesh i The temperature value of the vertex i of the face element M is obtained by interpolating the distance from the texture coordinates of the pixel point N to the texture coordinates of each vertex i to obtain the temperature value of the center point of the face element M, and the temperature value of the center point of the face element M is used as the temperature value of the pixel point N;

[0031] Step 4.4, repeat steps 4.1 to 4.3 to obtain the temperature of each pixel in the texture map.

[0032] In one embodiment of the present invention, step 5, voxelizing the volume grid into a flow field, comprises:

[0033] Step 5.1, in a scene editor, setting a cuboid region for the target region in the geometric model, so that the cuboid region just accommodates the target region in the geometric model;

[0034] Step 5.2, divide the rectangular area into a plurality of preset voxels, calculate the volume elements where the volume grid intersects the voxels, obtain the preset temperature values ​​and gas concentration values ​​in the volume elements intersecting the voxels, and calculate the average values, taking the average value of the temperature values ​​as the temperature value of the voxels, and taking the average value of the gas concentration values ​​as the gas concentration of the voxels.

[0035] In one embodiment of the present invention, step 6, performing ray tracing based on a multi-resolution grid to calculate the solid infrared radiation brightness of the target area of ​​the geometric model, and calculating the gas infrared radiation brightness of the target area of ​​the geometric model based on the ray tracing, includes:

[0036] Step 6.1, formulating a fourth surface mesh of a target resolution of the geometric model according to the distance between the observer and the geometric model;

[0037] Step 6.2, completely fitting the texture map for generating the temperature of each pixel point to the fourth surface mesh;

[0038] Step 6.3, emitting rays through a simulation sensor to perform ray tracing on the fourth surface mesh and the volume mesh, when the ray intersects with the fourth surface mesh, obtaining the temperature in the texture map of the intersection point, and calculating the solid infrared radiation brightness of the intersection point according to the temperature in the texture map of the intersection point and a preset emissivity;

[0039] Step 6.4, when the ray intersects the voxel, the infrared radiation brightness of the gas in the voxel is calculated according to the temperature value of the voxel, the gas concentration and the path length of the ray passing through the voxel;

[0040] Step 6.5, repeat steps 6.2 to 6.4 to calculate the infrared radiation brightness of all solids and all gases in the target area in the geometric model.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The target infrared calculation method based on multi-resolution grids provided by the present invention sets a structured grid for the target area of ​​the geometric model, interpolates the flow field data in the unstructured grid of the target area of ​​the geometric model into the uniform voxels of the structured grid to calculate the gas infrared radiation brightness of the target area of ​​the geometric model, and improves the calculation efficiency of the gas infrared radiation brightness of the geometric model by voxelizing the flow field.

[0043] 2. The target infrared calculation method based on multi-resolution grid provided by the present invention uses the surface grid to replace the geometric model surface to calculate the solid radiation brightness of the geometric model, copies the temperature data on the geometric model body grid to the first surface grid, obtains the second surface grid with the same proportion as the first surface grid through the obj file or gltf file of the geometric model, and the second surface grid is provided with the geometric coordinates of the surface grid of the geometric model, copies the second surface grid to the third surface grid, replaces the geometric coordinates of the third surface grid with texture coordinates according to the obj file or gltf file, and then establishes a first mapping from the second surface grid to the first surface grid, and establishes a second mapping from the texture map to the third surface grid. According to the first mapping and the second mapping, the temperature value of each pixel in the texture map is obtained, and the temperature values ​​of the surface grids with different resolutions can be obtained by simply mapping the texture map to the required multi-resolution surface grid, without calculating the temperature values ​​in the surface grids with different resolutions respectively for the surface grids with different resolutions, and further improves the calculation efficiency of the infrared radiation brightness on the basis of flow field voxelization.

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1It is a flowchart of a target infrared calculation method based on a multi-resolution grid provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the scheme according to the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0047] 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.

[0048] 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 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 more 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.

[0049] See also Figure 1 , Figure 1 : is a flow chart of a target infrared calculation method based on a multi-resolution grid provided by an embodiment of the present invention, and the target infrared calculation method specifically comprises the following steps:

[0050] Step 1, obtaining the first surface mesh in the volume mesh of the geometric model;

[0051] Specifically, according to the wall relationship and point-surface relationship in the volume mesh preset in the geometric model, a first surface mesh corresponding to the volume mesh is generated, in which the temperature value and gas concentration value of the geometric model are preset. Therefore, in the first surface mesh obtained through the volume mesh, the same surface element corresponding to the volume mesh also includes the corresponding temperature value, that is, the same surface element corresponding to the volume mesh in the first surface mesh has the temperature value of the surface element in the volume mesh copied.

[0052] Step 2, establishing a first mapping from the second surface mesh to the first surface mesh;

[0053] Specifically, the first mapping is a correspondence between the vertex coordinate projection of each face element in the second face mesh and the face element of the first face mesh.

[0054] Further, establishing a first mapping from the second surface mesh to the first surface mesh specifically includes:

[0055] Step 2.1, generating a second surface mesh according to the obj file or gltf file of the geometric model, wherein the second surface mesh has the geometric coordinates of the geometric model, and the second surface mesh has the same shape, size, coordinate axis direction and main direction of the geometric model as the first surface mesh;

[0056] In this embodiment, the geometric model is an airplane, and a model surface mesh of the same scale as the geometric model is obtained as the second surface mesh, and the second surface mesh has a different resolution from the first surface mesh. Specifically, an obj file or a gltf file of the airplane is obtained to generate a second surface mesh of the airplane model. The mesh resolution of the second surface mesh is generally different from the first surface mesh extracted from the volume mesh, and usually, the mesh resolution of the second surface mesh is lower than the mesh resolution of the first surface mesh.

[0057] Step 2.2, dividing the first surface mesh into m*n*k first grid spaces, each first grid space corresponds to a different face element of the first surface mesh contained in the first grid space, specifically, m, n and k are all positive integers greater than 0;

[0058] In this embodiment, the maximum coordinate point and the minimum coordinate point in the first surface mesh and the second surface mesh are obtained respectively. Specifically, the maximum coordinate point is the coordinate point with the maximum coordinate value in each coordinate axis direction in the three-dimensional coordinate axis where it is located, and the minimum coordinate point is the coordinate point with the minimum coordinate value in each coordinate axis direction in the three-dimensional coordinate axis where it is located. In addition, this embodiment also constructs a three-dimensional array of m*n*k corresponding to the first grid space according to the first surface mesh divided into m*n*k portions. The three-dimensional data is used to store the indexes of different face elements of the first surface mesh contained in each first grid space. For example, in the divided m*n*k portions of the first grid space, the indexes of face element 1, face element 2, and face element 7 are stored in the 2*2*5th portion of the first grid space.

[0059] Step 2.3, converting the vertex coordinates of each face element in the second face mesh to the coordinate system of the first face mesh, and calculating the first mesh space corresponding to the vertex coordinates of each face element in the second face mesh in the coordinate system of the first face mesh;

[0060] Specifically, the vertex coordinates of each face element in the second face mesh are transformed into an intermediate coordinate system, which is a coordinate system that keeps the coordinate axis direction of the second face mesh unchanged and takes the minimum coordinate point in the second face mesh as the coordinate origin. The vertex coordinates of each face element in the second face mesh in the intermediate coordinate system are transformed into the coordinate system of the first face mesh.

[0061] Step 2.4: Obtain the corresponding relationship between the vertex coordinate projection of each face element in the second face mesh and the face element in the first face mesh.

[0062] Specifically, first, according to the first grid space corresponding to the vertex coordinates of each face element in the second face mesh and the different face elements of the first face mesh corresponding to the first grid space, the vertex coordinates of each face element in the second face mesh are projected to the different face elements of the first face mesh corresponding to the corresponding first grid space. When the vertex coordinates are projected into the face element in the first face mesh corresponding to the corresponding first grid space, and the normal direction of the vertex is consistent with the normal direction of the face element in the corresponding first face mesh, then the distance between the vertex and the face element in the first face mesh with the consistent normal direction is calculated, and further, the correspondence between the face element of the first face mesh and the projection of the vertex coordinates when the distance is the shortest is the first mapping.

[0063] For example, a face element of the second face mesh includes three vertices: vertex l 1 , vertex l 2 and vertex l 3 The coordinate projections of these three vertices correspond to the surface element L on the first surface mesh. 1 , panel L 2 , panel L 3 , panel L 4 and face element L 5 , and vertex l 1 The coordinates of are projected onto the surface element L that is consistent with its normal direction 1 and face element L 2 , vertex l 2 The coordinates of are projected onto the surface element L that is consistent with its normal direction 3 and face element L 4 , vertex l 3 The coordinates of the projection are projected onto the surface element L that is consistent with its normal direction. 5 , since vertex l 1 The coordinates of the projection are projected onto the surface element L in the corresponding first surface mesh 1 and face element L 2 , and the surface element L 1 and face element L 2 The normal direction of the vertex l 1 The normal directions of the vertices are the same, so the vertex l is calculated separately 1 To surface element L1 The distance and vertex l 1 To surface element L 2 distance, and get vertex l 1 Distance to surface L 2 The distance to vertex l is the shortest. Similarly, we can calculate 2 The shortest distance to the face element, due to vertex l 3 There is only one matching face, so there is no need to calculate the shortest distance.

[0064] Step 3, establishing a second mapping of the texture map of the geometric model to the third surface mesh;

[0065] Specifically, the third surface mesh is a surface mesh with geometric model texture coordinates generated by copying the second surface mesh, and the second mapping is the correspondence between the center point projection of each pixel in the texture map of the geometric model and the face element of the third surface mesh.

[0066] Further, a second mapping of the texture map of the geometric model to the third surface mesh is established, specifically including:

[0067] Step 3.1, copy the second surface mesh to the third surface mesh, and replace the geometric coordinates of the vertex of each face element in the third surface mesh with the texture coordinates of the vertex;

[0068] In this embodiment, according to the obj file or gltf file of the geometric model, the geometric coordinates of the vertex of each face element in the third face mesh are replaced with the texture coordinates of the vertex.

[0069] Step 3.2, dividing the third surface mesh into p*q*1 third grid spaces, each third grid space corresponding to a different face element of the third surface mesh contained in the third grid space;

[0070] Specifically, p and q are both positive integers greater than 0. In this embodiment, the maximum coordinate point and the minimum coordinate point in the third surface grid are obtained. Specifically, the maximum coordinate point is the coordinate point with the largest coordinate value in each coordinate axis direction in the three-dimensional coordinate axis where it is located, and the minimum coordinate point is the coordinate point with the smallest coordinate value in each coordinate axis direction in the three-dimensional coordinate axis where it is located. In addition, according to dividing the third surface grid into p*q*1 third grid spaces, a p*q two-dimensional array corresponding to the third grid space is constructed, and the two-dimensional data is used to store different facet indexes of the third surface grid contained in each third grid space.

[0071] Step 3.3, obtain the texture map of the geometric model, calculate the third grid space corresponding to the center point of each pixel in the texture map, project the center point of each pixel to the face element in the corresponding third surface mesh in the corresponding third grid space, when the center point of the pixel is projected within the face element in the corresponding third surface mesh, the correspondence between the projection of the center point of the pixel and the face element in the corresponding third surface mesh is the second mapping.

[0072] Step 4: Obtain the temperature of each pixel in the texture map according to the first mapping and the second mapping;

[0073] Furthermore, step 4 specifically includes:

[0074] Step 4.1, according to the second mapping, obtain the face element M on the third face mesh corresponding to the projection of the center point of the pixel point N in the texture map;

[0075] Specifically, N and M are both positive integers greater than or equal to 1.

[0076] Step 4.2: Based on the face element M on the second face mesh and the first mapping, obtain the face element K of the first face mesh corresponding to the coordinate projection of the vertex i of the face element M: i , where i = 1, 2, ..., F, F represents the number of vertices of the face element M, i represents the vertex i of the face element M, K i Represents the face element of the first face mesh corresponding to the coordinate projection of the vertex i of the face element M;

[0077] Specifically, there are multiple vertices on the face element M, usually 3 or 4. For example, when the number of vertices on the face element M is 3, F = 3, i = 1, 2, 3, that is, the face element M includes vertex 1, vertex 2 and vertex 3. The face elements of the first face mesh corresponding to the coordinate projections of these three vertices are face elements K and i.e., 1 , panel K 2 and face element K 3 .

[0078] Step 4.3: Based on the surface element K of the first surface mesh i The temperature value of the vertex i of the face element M is obtained by interpolating the distance from the texture coordinates of the pixel point N to the texture coordinates of each vertex i to obtain the temperature value of the center point of the face element M, and the temperature value of the center point of the face element M is used as the temperature value of the pixel point N;

[0079] Specifically, the face element M on the third face mesh and the face element M on the second face mesh are the same face element in the geometric model.

[0080] Step 4.4: Repeat steps 4.1 to 4.3 to obtain the temperature of each pixel in the texture map.

[0081] In this embodiment, first, by traversing each pixel on the texture map and the two-dimensional array p*q, the bin index of the third surface mesh contained in the third grid space corresponding to each pixel is found. Since the third surface mesh is obtained by copying the second surface mesh, all points on the third surface mesh are the same as all points on the second surface mesh. Then, through all vertices on the second surface mesh, the bin index on the first surface mesh corresponding to all vertices on the second surface mesh is found, that is, the bin index on the first surface mesh corresponding to each pixel on the texture map can be obtained.

[0082] Step 5, voxelize the volume grid into flow field;

[0083] Generally, when scattering is ignored, the infrared radiation brightness of the geometric model usually includes the infrared radiation brightness of the gas and the radiation brightness of the solid. The target infrared calculation method based on the multi-resolution grid provided in this embodiment sets a structured grid for the target area of ​​the geometric model, and interpolates the flow field data in the unstructured grid of the target area of ​​the geometric model into the uniform voxels of the structured grid to calculate the infrared radiation brightness of the gas in the target area of ​​the geometric model. Specifically, the flow field voxelization of the volume grid includes the following steps:

[0084] Step 5.1, in the scene editor, set a cuboid region for the target region in the geometric model, so that the cuboid region just accommodates the target region in the geometric model;

[0085] In this embodiment, the target area of ​​the aircraft model is the entire aircraft, and the rectangular area contains the entire aircraft. In other embodiments, the target area of ​​the aircraft model is the high-temperature tail flame part behind the tail, so the rectangular area is set to only contain the high-temperature tail flame part behind the tail.

[0086] Step 5.2, divide the rectangular area into a plurality of preset voxels, calculate the volume elements where the volume grid intersects the voxels, obtain the preset temperature values ​​and gas concentration values ​​in the volume elements intersecting the voxels, and calculate the average values, taking the average value of the temperature values ​​as the temperature value of the voxel, and taking the average value of the gas concentration values ​​as the gas concentration of the voxel.

[0087] The target infrared calculation method based on multi-resolution grids provided in this embodiment improves the calculation efficiency of the infrared radiation brightness of the gas in the target area of ​​the geometric model by voxelizing the flow field.

[0088] Step 6: Perform ray tracing based on the multi-resolution grid to calculate the solid infrared radiation brightness of the target area of ​​the geometric model, and calculate the gas infrared radiation brightness of the target area of ​​the geometric model based on ray tracing.

[0089] Further, the infrared radiation brightness of the target area of ​​the geometric model includes the solid infrared radiation brightness of the target area and the gas infrared radiation brightness of the target area. Step 6 specifically includes:

[0090] Step 6.1, according to the distance between the observer and the geometric model, formulate the fourth surface mesh of the target resolution of the geometric model;

[0091] Step 6.2, completely fit the texture map that has generated the temperature of each pixel point to the fourth surface mesh;

[0092] Specifically, since the fourth surface mesh is consistent with the geometric model in shape and size, the texture map of the geometric model can be completely matched with the fourth surface mesh.

[0093] Step 6.3, tracing the fourth surface mesh and the volume mesh by emitting rays through the simulation sensor, when the ray intersects with the fourth surface mesh, obtaining the temperature in the texture map of the intersection point, and calculating the solid infrared radiation brightness of the intersection point according to the temperature in the texture map of the intersection point and the preset emissivity;

[0094] Step 6.4, when the ray intersects the voxel, the gas infrared radiation brightness of the voxel is calculated according to the temperature value of the voxel, the gas concentration and the path length of the ray passing through the voxel;

[0095] Step 6.5: Repeat steps 6.2 to 6.4 to calculate the infrared radiation brightness of all solids and all gases in the target area of ​​the geometric model.

[0096] The target infrared calculation method based on multi-resolution grid provided in this embodiment uses the surface grid to replace the geometric model surface to calculate the solid radiation brightness of the geometric model. However, when the distance between the viewpoint and the geometric model is different, the resolution of the surface grid needs to be dynamically switched. In the traditional method, the temperature values ​​in the surface grids of different resolutions need to be calculated for the surface grids of different resolutions, and the calculation efficiency is low. In this embodiment, the temperature data on the geometric model body grid is copied to the first surface grid, and the second surface grid with the same proportion as the first surface grid is obtained through the obj file or gltf file of the geometric model, and the second surface grid is provided with the geometric coordinates of the surface grid of the geometric model, and the second surface grid is copied to the third surface grid. According to the obj file or gltf file, the geometric coordinates of the third surface grid are replaced with texture coordinates, and then the first mapping of the second surface grid to the first surface grid is established, and the second mapping of the texture map to the third surface grid is established. According to the first mapping and the second mapping, the temperature value of each pixel in the texture map is obtained, and the temperature value of the surface grids of different resolutions can be obtained by mapping the texture map to the required multi-resolution surface grid, and then the solid radiation brightness of the geometric model can be obtained. There is no need to calculate the temperature values ​​in surface grids of different resolutions separately, which greatly improves the efficiency of ray tracing and further improves the calculation efficiency of infrared radiation brightness based on flow field voxelization.

[0097] The target infrared calculation method of this embodiment simplifies the complexity of infrared radiation brightness calculation within the volume mesh by voxelizing the volume mesh of the geometric model, and switches surface meshes of different resolutions according to distance, so that the target heat calculated on one surface mesh can be mapped to a multi-resolution surface mesh, thereby improving the efficiency of ray tracing.

[0098] 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 target infrared calculation method based on multi-resolution grids, characterized in that: include: S1, obtaining a first surface mesh in a volume mesh of a geometric model, wherein the volume mesh is pre-set with a temperature value and a gas concentration value of the geometric model, and in the first surface mesh, the same face element corresponding to the volume mesh includes a corresponding temperature value; S2, establishing a first mapping from a second surface mesh to the first surface mesh, wherein the second surface mesh has geometric coordinates of the geometric model, and the second surface mesh and the first surface mesh have the same shape, size, coordinate axis direction, and main direction of the geometric model, and the first mapping is a correspondence between a vertex coordinate projection of each face element in the second surface mesh and a face element of the first surface mesh; The mesh resolution of the second surface mesh is lower than the mesh resolution of the first surface mesh; S3, establishing a second mapping from the texture map of the geometric model to a third surface mesh, wherein the third surface mesh is a surface mesh having texture coordinates of the geometric model generated by copying the second surface mesh, and the second mapping is a correspondence between a projection of a center point of each pixel in the texture map of the geometric model and a facet of the third surface mesh; S4. Obtaining the temperature of each pixel in the texture map according to the first mapping and the second mapping; S5, voxelizing the volume grid into flow field; S6, performing ray tracing based on a multi-resolution grid to calculate the solid infrared radiation brightness of the target area of ​​the geometric model, and calculating the gas infrared radiation brightness of the target area of ​​the geometric model based on the ray tracing, including: S6.1, formulating a fourth surface mesh of a target resolution of the geometric model according to a distance between an observer and the geometric model; S6.2, completely fitting the texture map to the fourth surface mesh; S6.3, emitting rays through a simulation sensor to perform ray tracing on the fourth surface mesh and the volume mesh, and when the rays intersect the fourth surface mesh, obtaining the temperature in the texture map of the intersection point, and calculating the solid infrared radiation brightness of the intersection point according to the temperature in the texture map of the intersection point and a preset emissivity; S6.4, when the ray intersects a voxel, calculating the gas infrared radiation brightness of the voxel according to the temperature value of the voxel, the gas concentration and the path length of the ray passing through the voxel; S6.

5. Repeat S6.2 to S6.4 to calculate the infrared radiation brightness of all solids in the target area and the infrared radiation brightness of all gases in the target area.

2. The target infrared calculation method based on multi-resolution grid according to claim 1 is characterized in that: S1. Obtaining a first surface mesh in a volume mesh of a geometric model, including generating a first surface mesh corresponding to the volume mesh according to a wall relationship and a point-surface relationship in the volume mesh preset for the geometric model, wherein the volume mesh is preset with a temperature value and a gas concentration value of the geometric model.

3. The target infrared calculation method based on multi-resolution grid according to claim 1 is characterized in that: S2. Establishing a first mapping from the second surface mesh to the first surface mesh, comprising: S2.

1. Generate a second surface mesh according to the obj file or gltf file of the geometric model, wherein the second surface mesh has the geometric coordinates of the geometric model, and the second surface mesh has the same shape, size, coordinate axis direction and main direction of the geometric model as the first surface mesh; S2.2, dividing the first surface mesh into m*n*k first grid spaces, each first grid space corresponding to a different face element of the first surface mesh contained therein, wherein m, n and k are all positive integers greater than 0; S2.3, converting the vertex coordinates of each face element in the second face mesh to the coordinate system of the first face mesh, and calculating the first mesh space corresponding to the vertex coordinates of each face element in the second face mesh in the coordinate system of the first face mesh; S2.

4. Obtain a correspondence between the vertex coordinate projection of each face element in the second face mesh and the face element in the first face mesh.

4. The target infrared calculation method based on multi-resolution grid according to claim 3 is characterized in that: S2.3, converting the vertex coordinates of each facet in the second face mesh to the coordinate system of the first face mesh, comprising: Converting the vertex coordinates of each face element in the second face mesh to an intermediate coordinate system, wherein the intermediate coordinate system is a coordinate system that keeps the coordinate axis direction of the second face mesh unchanged and takes the minimum coordinate point in the second face mesh as the coordinate origin; The vertex coordinates of each face element in the second face mesh in the intermediate coordinate system are converted to the coordinate system of the first face mesh.

5. The target infrared calculation method based on multi-resolution grid according to claim 3 is characterized in that: S2.4, obtaining a correspondence between the vertex coordinate projection of each face element in the second face mesh and the face element of the first face mesh, including: According to the first grid space corresponding to the vertex coordinates of each face element in the second face mesh and different face elements of the first face mesh corresponding to the first grid space, projecting the vertex coordinates of each face element in the second face mesh to different face elements of the first face mesh corresponding to the corresponding first grid space; When the vertex coordinates are projected into the face element in the first face mesh corresponding to the corresponding first mesh space, and the normal direction of the vertex is consistent with the normal direction of the face element in the corresponding first face mesh, the distance between the vertex and the face element in the first face mesh with the corresponding normal direction is calculated, and the correspondence between the face element of the first face mesh and the projection of the vertex coordinates when the distance is shortest is the first mapping.

6. The target infrared calculation method based on multi-resolution grid according to claim 3 is characterized in that: S3, establishing a second mapping of the texture map of the geometric model to the third surface mesh, including: S3.

1. Copy the second surface mesh to a third surface mesh, and replace the geometric coordinates of the vertices of each facet in the third surface mesh with the texture coordinates of the vertices; S3.2, dividing the third surface grid into p*q*1 third grid spaces, each third grid space corresponding to a different face element of the third surface grid contained therein, wherein p and q are both positive integers greater than 0; S3.

3. Obtain a texture map of the geometric model, calculate the third grid space corresponding to the center point of each pixel in the texture map, and project the center point of each pixel to the face element in the corresponding third surface mesh in the corresponding third grid space. When the center point of the pixel is projected within the face element in the corresponding third surface mesh, the correspondence between the projection of the center point of the pixel and the face element in the corresponding third surface mesh is the second mapping.

7. The target infrared calculation method based on multi-resolution grid according to claim 6 is characterized in that: S4. Obtaining the temperature of each pixel in the texture map according to the first mapping and the second mapping, including: S4.

1. According to the second mapping, obtain a face element M on the third face mesh corresponding to the projection of the center point of the pixel point N in the texture map, wherein N and M are both positive integers greater than or equal to 1; S4.2, according to the face element M on the second face mesh and the first mapping, obtain the face element K of the first face mesh corresponding to the coordinate projection of the vertex i of the face element M i , wherein i=1,2,…,F, F represents the number of vertices of the face element M, and i represents the vertex i of the face element M; the face element M on the third face mesh and the face element M on the second face mesh are the same face element in the geometric model; S4.

3. Based on the surface element K of the first surface mesh i The temperature value of the vertex i of the face element M is obtained by interpolating the distance from the texture coordinates of the pixel point N to the texture coordinates of each vertex i to obtain the temperature value of the center point of the face element M, and the temperature value of the center point of the face element M is used as the temperature value of the pixel point N; S4.4, repeat S4.1 to S4.3 to obtain the temperature of each pixel in the texture map.

8. The target infrared calculation method based on multi-resolution grid according to claim 7 is characterized in that: S5, voxelizing the volume grid into a flow field, including: S5.

1. In a scene editor, setting a cuboid region for the target region in the geometric model, so that the cuboid region just accommodates the target region in the geometric model; S5.

2. Divide the rectangular area into a plurality of preset voxels, calculate the volume elements where the volume grid intersects the voxels, obtain the preset temperature values ​​and gas concentration values ​​in the volume elements intersecting the voxels, and perform average calculations, taking the average value of the temperature values ​​as the temperature value of the voxels, and taking the average value of the gas concentration values ​​as the gas concentration of the voxels.

Images