BSDF modeling method based on measured data

Abstract

The present invention belongs to the technical field of non-sequential ray tracing, and in particular relates to a BSDF modeling method based on measured data. The method comprises the following steps: S1: assuming that the range of motion of the photodetector corresponds to the angle range of the solid angle in the spherical coordinate system as #imgabs0#, dividing the solid angle into #imgabs1# sub-regions at equal angular intervals, and constructing the BSDF measurement values ​​of each sub-region into a BSDF matrix according to the position of each sub-region; S2: expanding the BSDF matrix and truncating the boundaries to obtain a weighted BSDF matrix; S3: calculating the center value coordinates of the sub-regions to which each element of the weighted BSDF matrix corresponds, and converting the center value coordinates of each sub-region from the angular space to the cosine space to complete the two-dimensional modeling of the BSDF. The present invention reduces the influence range of the BSDF at the boundary position, thereby reducing the model deviation, and obtains good modeling results.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-sequential ray tracing, and in particular relates to a BSDF modeling method based on measured data. Background Art

[0002] When light passes through an optical surface, the roughness of the surface creates a scattering effect. This scattering effect causes light to refract and reflect, while also generating light in other directions. The bidirectional scattering distribution function (BSDF) effectively describes the scattering effect of optical surfaces on light, and therefore plays an important role in fields such as stray radiation analysis. Only after completing BSDF (bidirectional scattering distribution function) measurements for various materials can the convenient application of material BSDF models be realized. In this context, two-dimensional modeling technology based on BSDF is particularly critical.

[0003] Currently, directly constructing models using interpolation or fitting methods based on measured BSDF data often results in complex processes. Improper interpolation methods can lead to significant deviations between calculated results and measured data, adversely affecting the design of high-precision optical systems. Simulation analysis often consumes significant time due to complex modeling, increasing time costs. Summary of the Invention

[0004] In view of this, the present invention aims to provide a BSDF modeling method based on measured data to solve the problem that the existing modeling technology is complex, often time-consuming and increases time costs. During the overall modeling, the present invention reduces the influence range of BSDF at the boundary position, thereby reducing the model deviation and obtaining good modeling results.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] A BSDF modeling method based on measured data specifically includes the following steps:

[0007] S1: Assume that the moving range of the photoelectric detector corresponds to the solid angle range in the spherical coordinate system. , divide the solid angle into equal angular intervals Sub-regions, according to the position of each sub-region, the BSDF measurement value of each sub-region is constructed into a BSDF matrix;

[0008] S2: Expand and truncate the BSDF matrix to obtain the weighted BSDF matrix;

[0009] S3: Calculate the center value coordinates of the sub-regions corresponding to each element of the weighted BSDF matrix, and convert the center value coordinates of each sub-region from the angle space to the cosine space to complete the two-dimensional modeling of the BSDF.

[0010] Furthermore, in step S1, the number of samples taken by the photodetector in the zenith angle direction is , the number of samples taken by the photodetector in the azimuth direction is , the angular coordinates of the sampling point obtained by the photodetector ( , )for:

[0011] ;

[0012] ;

[0013] in, For Uniform generation within the interval Points, For Uniform generation within the interval Points, is the i-th zenith angle, is the jth azimuth.

[0014] Furthermore, step S2 specifically includes the following steps:

[0015] S21: Copy each element of the BSDF matrix to obtain a dimension of Matrix of

[0016] S22: The copied dimension is The peripheral elements of the matrix are deleted to obtain the weighted BSDF matrix.

[0017] Furthermore, the weighted BSDF matrix is ​​of dimension The corner elements, boundary elements excluding corner elements, and internal elements of the weighted BSDF matrix are weighted in a ratio of 4:2:1.

[0018] Furthermore, step S3 specifically includes the following steps:

[0019] S31: Calculate the center value coordinates of each sub-region of the weighted BSDF matrix ( , ):

[0020] ;

[0021] ;

[0022] ;

[0023] ;

[0024] in, is the angle difference between two adjacent zenith angles, is the angle difference between two adjacent azimuth angles, m is the subscript of the expanded zenith angle, and the total , n is the subscript of the azimuth after expansion, a total of indivual, is the center value of the mth zenith angle, The center value of the nth azimuth;

[0025] S32: Convert the center value coordinates of each sub-region from the angle space to the cosine space:

[0026] ;

[0027] in, is the coordinate component of the x direction in the three-dimensional cosine space coordinate system after converting the center value of the m-th zenith angle and the center value of the n-th azimuth angle to the cosine space. is the coordinate component in the y direction in the three-dimensional cosine space coordinate system after converting the center value of the m-th zenith angle and the center value of the n-th azimuth angle to cosine space;

[0028] S33: The center point of each sub-region in the cosine space corresponds one-to-one to each element value of the weighted BSDF matrix, completing the two-dimensional modeling of the BSDF.

[0029] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0030] The present invention creates the BSDF modeling method based on measured data, which performs modeling based on the measured two-dimensional BSDF. During the overall modeling, the influence range of the BSDF at the boundary position is reduced, thereby reducing the model deviation, thereby obtaining good modeling results. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 A flowchart of a BSDF modeling method based on measured data according to an embodiment of the present invention is provided;

[0033] Figure 2 A schematic diagram of the BSDF matrix replication process described in an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of the BSDF matrix clipping process described in an embodiment of the present invention;

[0035] Figure 4 A schematic diagram of the structure of the weighted BSDF matrix described in an embodiment of the present invention;

[0036] Figure 5 A schematic diagram of the principle of sub-region division according to an embodiment of the present invention;

[0037] Figure 6 This is a two-dimensional BSDF modeling rendering of the embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0039] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0040] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0041] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0042] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0043] like Figure 1 As shown, the present invention provides a BSDF modeling method based on measured data, which specifically includes the following steps:

[0044] S1: Assume that the moving range of the photoelectric detector corresponds to the solid angle range in the spherical coordinate system. , divide the solid angle into equal angular intervals Sub-regions, according to the position of each sub-region, the BSDF measurement value of each sub-region is constructed into a BSDF matrix;

[0045] S2: Expand and truncate the BSDF matrix to obtain the weighted BSDF matrix;

[0046] S3: Calculate the center value coordinates of the sub-regions corresponding to each element of the weighted BSDF matrix, and convert the center value coordinates of each sub-region from the angle space to the cosine space to complete the two-dimensional modeling of the BSDF.

[0047] The present invention discloses a process for modeling based on the measured BSDF data, where the unit of BSDF is per steradian ( / sr). Assuming that the photodetector measures two orthogonal directions, the sensor of the photodetector realizes the zenith angle through a precision turntable. Direction and azimuth A two-dimensional rotational scan in the direction of the rotational scan can be performed to obtain a series of discrete BSDF measurements. After the measurement is completed, a model needs to be established for these discrete BSDF measurements on the overall definition domain. After the BSDF measurement is performed at a certain location, the influence range of the BSDF measurement value needs to be considered when building the overall model. The BSDF measurement value obtained at the boundary location often has reduced continuity and accuracy. Therefore, during the modeling process, the area affected by the BSDF measurement value at the boundary location needs to be weakened, and its weight ratio needs to be reduced compared to the non-boundary area.

[0048] In some embodiments, in step S1, the number of samples taken by the photodetector in the zenith angle direction is , the number of samples taken by the photodetector in the azimuth direction is , the angular coordinates of the sampling point obtained by the photodetector ( , )for:

[0049] ;

[0050] ;

[0051] in, For Uniform generation within the interval Points, For Uniform generation within the interval Points, is the i-th zenith angle, is the jth azimuth.

[0052] It should be noted that when the photoelectric detector is measured, uniform sampling is performed at fixed angle intervals, and the number of samples in the two-dimensional space is .

[0053] Furthermore, the BSDF measurement values ​​of each sub-region are constructed into a BSDF matrix according to the position of each sub-region. For example, if the sub-regions are arranged in a 3×3 grid, then the BSDF matrix is ​​a 3×3 matrix. The BSDF measurement values ​​of the three sub-regions in the first row of the 3×3 grid are solved from left to right as the first row elements of the 3×3 matrix, and the same applies to other positions.

[0054] In some embodiments, step S2 specifically includes the following steps:

[0055] S21: Copy each element of the BSDF matrix to obtain a dimension of Matrix of

[0056] S22: The copied dimension is The peripheral elements of the matrix are deleted to obtain the weighted BSDF matrix.

[0057] In some embodiments, the weighted BSDF matrix is ​​of dimension The corner elements, boundary elements excluding corner elements, and internal elements of the weighted BSDF matrix are weighted in a ratio of 4:2:1.

[0058] For example: Assume that the photodetector is uniformly sampled at a fixed angle interval, and the corresponding sub-regions are obtained, and the BSDF measurement value of each sub-region is obtained. According to the position of the sub-region, the BSDF measurement value of each sub-region is constructed into a BSDF matrix, such as Figure 2As shown, assuming that a 4×4 BSDF matrix is ​​obtained by sampling, assuming that the 16 sub-regions are numbered in the order from left to right and from top to bottom, and each element of the BSDF matrix is ​​copied horizontally and vertically, thus forming a dimension of Considering the measurement accuracy of the boundary, such as Figure 3 As shown, Figure 2 The matrix generated in is truncated to reduce the impact range of the boundary. Finally, the following is generated: Figure 4 In summary, the matrix dimension of BSDF before transformation is , the matrix dimension of the transformed BSDF is At this point, the BSDF matrix expansion transformation is complete. After the transformation, the ratio of the influence ranges of the interior, boundary (excluding the four corners, a total of 16), and corner (4) is 4:2:1. This is because the weight of the boundary BSDF measurement values ​​is slightly reduced during modeling to account for errors and continuity issues in the boundary BSDF measurement values.

[0059] In some embodiments, step S3 specifically includes the following steps:

[0060] Step S3 specifically includes the following steps:

[0061] S31: Calculate the center value coordinates of each sub-region of the weighted BSDF matrix ( , ):

[0062] ;

[0063] ;

[0064] ;

[0065] ;

[0066] in, is the angle difference between two adjacent zenith angles, is the angle difference between two adjacent azimuth angles, m is the subscript of the expanded zenith angle, and the total , m=1, 2, ..., , n is the subscript of the expanded azimuth angle, a total of , n=1, 2, ..., , is the center value of the mth zenith angle, The center value of the nth azimuth;

[0067] S32: Convert the center value coordinates of each sub-region from the angle space to the cosine space:

[0068] ;

[0069] in, is the coordinate component of the x direction in the three-dimensional cosine space coordinate system after converting the center value of the m-th zenith angle and the center value of the n-th azimuth angle to the cosine space. is the coordinate component in the y direction in the three-dimensional cosine space coordinate system after converting the center value of the m-th zenith angle and the center value of the n-th azimuth angle to cosine space;

[0070] S33: The center point of each sub-region in the cosine space corresponds one-to-one to each element value of the weighted BSDF matrix, completing the two-dimensional modeling of the BSDF.

[0071] like Figure 5 As shown, after the BSDF matrix transformation is completed, the sub-area corresponding to the new BSDF matrix (weighted BSDF matrix) is obtained according to the matrix after the BSDF matrix transformation. Since the present invention expands the number of BSDF measurement values, the number of angles corresponding to the BSDF measurement values ​​also needs to be expanded. The angle corresponding to each solid angle is:

[0072] ;

[0073] ;

[0074] Then the center value coordinates of each sub-region can be calculated:

[0075] ;

[0076] ;

[0077] Generally, BSDF generated values ​​are often expressed in cosine coordinates, so the center value coordinates of the angle in the spherical coordinate system are transferred to the cosine space:

[0078] ;

[0079] Each center point or Each corresponds to a sub-region of the measurement range, and the BSDF generated value in the sub-region is the BSDF measurement value of the transformed BSDF matrix. At this point, the establishment of the two-dimensional BSDF model is completed.

[0080] Using a set of measured BSDF data of a strongly anisotropic scatterer, the two-dimensional BSDF modeling is performed on the measured BSDF data using the above modeling method. The modeling results are as follows: Figure 6 shown.

[0081] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0082] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A BSDF modeling method based on measured data, characterized by: The specific steps include: S1: Assume that the moving range of the photoelectric detector corresponds to the solid angle range in the spherical coordinate system. , divide the solid angle into equal angular intervals Sub-regions, according to the position of each sub-region, the BSDF measurement value of each sub-region is constructed into a BSDF matrix; In step S1, the number of samples taken by the photodetector in the zenith angle direction is , the number of samples taken by the photodetector in the azimuth direction is , the angular coordinates of the sampling point obtained by the photodetector ( , )for: ； ； in, For Uniform generation within the interval Points, For Uniform generation within the interval Points, is the i-th zenith angle, is the jth azimuth; S2: Expand and truncate the BSDF matrix to obtain the weighted BSDF matrix; Step S2 specifically includes the following steps: S21: Copy each element of the BSDF matrix to obtain a dimension of Matrix of S22: The copied dimension is Delete the peripheral elements of the matrix to obtain the weighted BSDF matrix; S3: Calculate the center value coordinates of the sub-regions corresponding to each element of the weighted BSDF matrix, and convert the center value coordinates of each sub-region from the angle space to the cosine space to complete the two-dimensional modeling of the BSDF; Step S3 specifically includes the following steps: S31: Calculate the center value coordinates of each sub-region of the weighted BSDF matrix ( , ): ； ； ； ； in, is the angle difference between two adjacent zenith angles, is the angle difference between two adjacent azimuth angles, m is the subscript of the expanded zenith angle, and the total , n is the subscript of the azimuth after expansion, a total of indivual, is the center value of the mth zenith angle, The center value of the nth azimuth; S32: Convert the center value coordinates of each sub-region from the angle space to the cosine space: ； in, is the coordinate component of the x direction in the three-dimensional cosine space coordinate system after converting the center value of the m-th zenith angle and the center value of the n-th azimuth angle to the cosine space. is the coordinate component in the y direction in the three-dimensional cosine space coordinate system after converting the center value of the m-th zenith angle and the center value of the n-th azimuth angle to cosine space; S33: The center point of each sub-region in the cosine space corresponds one-to-one to each element value of the weighted BSDF matrix, completing the two-dimensional modeling of the BSDF.

2. The BSDF modeling method based on measured data according to claim 1, characterized in that: The weighted BSDF matrix is ​​of dimension The corner elements, boundary elements excluding corner elements, and internal elements of the weighted BSDF matrix are weighted in a ratio of 4:2:1.

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