A quantitative calculation method for coupled transmission of infrared multiple radiation sources

Abstract

The present invention discloses a quantitative calculation method for infrared multi-radiation source coupled transmission, comprising: obtaining three-dimensional scene information, and dividing the scene into a number of triangular facets; calculating the angular coefficient between each triangular facet; calculating the spectral radiance of the object in the scene; and calculating the spectral radiance of the scene according to the angular coefficient and the spectral radiance of the object. The present invention realizes the quantitative calculation of infrared multi-radiation source coupled transmission by using a radiance algorithm, and can output the radiance distribution of the scene in different spectral bands in the form of an image, making the algorithm easier to implement, and for multi-radiation source scenes, there is no need to perform a large amount of sampling of light sources and light, and the calculation rate is faster.

Description

Technical Field

[0001] The invention belongs to the technical field of infrared scene simulation, and in particular relates to a quantitative calculation method for coupled transmission of infrared multiple radiation sources. Background Art

[0002] Infrared technology is a passive detection technology. Since all objects can radiate infrared rays, infrared equipment can work in a passive way. Compared with radar, it has the advantages of simplicity, small size, light weight, high resolution, good concealment, and strong anti-interference ability. Compared with visible light, it has the advantages of strong ability to penetrate smoke and dust and can work day and night. Therefore, it is widely used in various fields. Among them, infrared scene simulation is an important aspect of infrared technology application.

[0003] Traditional infrared scene simulation technologies mainly include ray tracing, path tracing, bidirectional path tracing and other physically based rendering technologies. These methods mainly use a large number of rays emitted from the camera or light source to bounce on the surface or inside of the scene's objects. During this bouncing process, the energy ultimately carried by the rays from the light source to the camera is calculated based on the optical properties of the object's surface, which involves light source sampling and ray sampling technology.

[0004] However, for infrared scenes, all objects with temperatures above absolute zero are non-negligible radiation sources, and the calculation rate of traditional algorithms generally decreases nonlinearly with the number of light sources. Therefore, the existing physically based rendering methods (radiation calculation technology) have the disadvantage of too low a rate for the radiation calculation of complex infrared scenes, and the algorithm complexity is too high and difficult to implement. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a quantitative calculation method for infrared multi-radiation source coupling transmission. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] A quantitative calculation method for infrared multi-radiation source coupled transmission, comprising:

[0007] Step 1: Obtain three-dimensional scene information and divide the scene into a number of triangular facets;

[0008] Step 2: Calculate the angular coefficients between each triangular face;

[0009] Step 3: Calculate the spectral radiance of objects in the scene;

[0010] Step 4: Calculate the spectral radiance of the scene according to the angular coefficient and the spectral radiance of the object.

[0011] In one embodiment of the present invention, step 2 comprises:

[0012] 21) For a certain triangle in the scene, it is regarded as the target patch, and the other triangles in the scene are regarded as source patches;

[0013] 22) Based on the semi-cube algorithm, the OpenGL rendering technology is used to project the visible area of ​​a source patch to the target patch on the semi-cube at the center and normal side of the target patch, and obtain several micro-element patches corresponding to the current source patch;

[0014] 23) According to the solid angle projection theorem, the angle coefficient of each micro-element of the current source surface to the target surface is calculated through the projection area;

[0015] 24) Accumulating the angular coefficients of all micro-element patches of the current source patch to the target patch to obtain the angular coefficient of the current source patch to the target patch;

[0016] 25) Repeat steps 22)-24) to obtain the angular coefficients of all source patches to the target patch.

[0017] In one embodiment of the present invention, the calculation formula of the angle coefficient in step 23) is:

[0018]

[0019] Among them, dF 12 It represents the angular coefficient of a microelement of source patch 1 to target patch 2. θ1 and θ2 are the angles between the center line of the two patches and the normal lines of the two patches, respectively. 12 is the distance between the two patches, and A2 is the area of ​​target patch 2.

[0020] In one embodiment of the present invention, before calculating the spectral radiance of the object in the scene in step 3, the method further includes:

[0021] Determine the spectral bands to be calculated and the spectral band subdivision level.

[0022] In one embodiment of the present invention, step 3 comprises:

[0023] 31) Calculate the blackbody spectrum spontaneous radiation M of the object temperature λbb , the calculation formula is as follows:

[0024]

[0025] Where c1 represents Planck's first radiation constant, c2 represents Planck's second radiation constant, λ represents the current spectrum wavelength, and T represents the absolute temperature of the black body;

[0026] 32) Calculate the spectral spontaneous radiation M of the object according to the black body spectral spontaneous radiation of the object temperature λ , the calculation formula is as follows:

[0027] M λ =(1-r)·M λbb

[0028] Where r is the spectral reflectance of the object;

[0029] 33) Calculate the spectral radiance M of the object in a certain spectral band according to the spectral spontaneous radiation of the object λ～λ+Δλ , the calculation formula is as follows:

[0030]

[0031] Among them, Δλ represents the spectral subdivision.

[0032] In one embodiment of the present invention, step 4 comprises:

[0033] 41) According to the reciprocity theorem of angular coefficients, the angular coefficient of the source patch to the target patch is converted into the angular coefficient of the target patch to the source patch;

[0034] 42) Calculate the spectral radiance emitted by the target patch under single reflection based on the angular coefficient of the target patch to the source patch The calculation formula is as follows:

[0035]

[0036] Among them, E λ represents the spectral spontaneous radiation of the target patch, F 21 Indicates the angular coefficient of target patch 2 to source patch 1, E' λ represents the spectral spontaneous radiation of the source patch, and r is the spectral reflectivity of the object;

[0037] 43) According to the spectral radiance emitted by the target patch in the case of single reflection Calculate the spectral radiance emitted by the target patch under two reflections The calculation formula is as follows:

[0038]

[0039] in, is the direct illumination spectral radiance of the source patch, and

[0040] 44) Iterate the calculation until the scene is saturated, and obtain the spectral radiance emitted by the target patch under n reflections The calculation formula is as follows:

[0041]

[0042] Where n≥3, represents the spectral radiance of the source patch after n-1 radiation reflections, and

[0043] 45) Integrate the obtained spectral radiances over a certain spectrum segment to obtain the spectral radiance of the scene in the current spectrum segment. The formula is expressed as:

[0044]

[0045] Among them, Δλ represents the spectral subdivision.

[0046] Beneficial effects of the present invention:

[0047] 1. The present invention realizes the quantitative calculation of infrared multi-radiation source coupling transmission by using the radiometric algorithm, and can output the radiance distribution of scenes in different spectral bands in the form of images, making the algorithm easier to implement, and for multi-radiation source scenes, there is no need to perform a large number of sampling of light sources and light, and the calculation rate is faster;

[0048] 2. The present invention uses the OpenGL 3D rendering engine, based on the solid angle projection theorem, combined with the Hemi-cube algorithm, to calculate the angular coefficients between the triangular facets in the scene, which greatly improves the calculation speed;

[0049] 3. The present invention is based on the laws of physical radiation and calculates the spectral spontaneous radiation of an object from the object's temperature and reflectivity. The calculation result has high authenticity and credibility.

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a flow chart of a quantitative calculation method of infrared multi-radiation source coupled transmission provided by an embodiment of the present invention;

[0052] Figure 2 It is a detailed flow chart of a quantitative calculation method for infrared multi-radiation source coupled transmission provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0054] Embodiment 1

[0055] The radiosity algorithm is a lightweight, low-time rendering technology suitable for infrared scenes. It is a physically based rendering technology in computer graphics. The algorithm (rendering technology) is based on radiosity and is applied to the radiation calculation of Lambertian (ideal diffuse reflector) scenes. The algorithm regards each object in the scene as a light source, and calculates the irradiance obtained by multiple reflections based on its geometric relationship with other objects and its own radiation characteristics. The irradiance is added to the radiation of the object itself to obtain the overall radiance of the object. This algorithm is completely based on physics, so it can perform quantitative simulation calculations on the characteristics of real infrared scenes.

[0056] Based on this, the present invention proposes a quantitative calculation method for infrared multi-radiation source coupling transmission. Figure 1-2 , Figure 1 is a flow chart of a quantitative calculation method for infrared multi-radiation source coupled transmission provided by an embodiment of the present invention, Figure 2 It is a detailed flow chart of a quantitative calculation method of infrared multi-radiation source coupled transmission provided by an embodiment of the present invention, which includes:

[0057] Step 1: Obtain three-dimensional scene information and divide the scene into a number of triangular faces.

[0058] First, the three-dimensional scene information is obtained, which mainly includes the temperature, geometric composition and three-dimensional transformation information of the objects in the scene.

[0059] Then, the scene is subdivided to obtain a scene consisting of a set of triangular facets.

[0060] Step 2: Calculate the angle coefficients between each triangle.

[0061] In this embodiment, the angular coefficient between each triangular facet is also the geometric factor between the facets, and the calculation process thereof is as follows:

[0062] 21) For a certain triangle in the scene, it is regarded as the target patch, and the other triangles in the scene are regarded as source patches.

[0063] 22) Based on the semi-cube algorithm, OpenGL rendering technology is used to project the visible area of ​​a source patch on the center and normal side of the target patch, respectively, to obtain several micro-element patches corresponding to the current source patch.

[0064] 23) According to the solid angle projection theorem, the angular coefficient of each micro-element of the current source patch to the target patch is calculated through the projection area.

[0065] Specifically, since the angular coefficient is only related to the position and area of ​​the source patch projected on the hemicube, the angular coefficient of the micro-element patch on the hemicube to the center of the target patch, that is, the angle coefficient, can be calculated in advance and saved in an array. Specifically, the calculation formula for the angle coefficient is:

[0066]

[0067] Among them, dF 12 It represents the angular coefficient of a microelement of source patch 1 to target patch 2. θ1 and θ2 are the angles between the center line of the two patches and the normal lines of the two patches, respectively. 12 is the distance between the two patches, and A2 is the area of ​​target patch 2.

[0068] 24) Accumulate the angular coefficients of all micro-element patches of the current source patch to the target patch to obtain the angular coefficient of the current source patch to the target patch.

[0069] Specifically, according to the additivity of the angular coefficients, the angular coefficient of the source patch to the target patch is equal to the sum of the angular coefficients of all projected micro-element patches. After obtaining the position of the projected micro-element patch of the source patch, the corresponding angular coefficients in the array can be directly accumulated to obtain the angular coefficient F of the current source patch 1 to the target patch 2. 12 .

[0070] 25) Repeat steps 22)-24) to obtain the angular coefficients of all source patches to the target patch.

[0071] The present invention uses an OpenGL three-dimensional rendering engine, based on the solid angle projection theorem and combined with a Hemi-cube algorithm, to calculate the angular coefficients between triangular facets in a scene, thereby greatly improving the calculation rate.

[0072] Step 3: Calculate the spectral radiance of objects in the scene.

[0073] Specifically, before calculating the spectral radiance of an object in a scene, it is necessary to first determine the spectral band to be calculated and the degree of spectral band subdivision.

[0074] In this embodiment, the spectrum segments and the spectrum segment subdivision levels can be customized, which is not required in this embodiment.

[0075] After determining the spectrum and the spectrum segmentation, the radiation calculation of each discrete spectrum segment is performed, including:

[0076] 31) Calculate the blackbody spectrum spontaneous radiation M of the object temperature λbb

[0077] Specifically, according to Planck's blackbody radiation formula

[0078]

[0079] The spontaneous radiation of the blackbody spectrum with the same object temperature can be obtained, where c1 represents Planck's first radiation constant, c2 represents Planck's second radiation constant, λ represents the current spectrum wavelength, and T represents the absolute temperature of the blackbody.

[0080] 32) Calculate the spectral spontaneous radiation M of the object according to the black body spectral spontaneous radiation of the object temperature λ .

[0081] Specifically, in a thermal equilibrium environment, the sum of the emissivity, transmittance, and reflectivity of an object is equal to 1. Ignoring the radiation transmitted by the object, the emissivity and reflectivity are complementary, and the calculation formula for the spectral spontaneous radiation of the object is:

[0082] M λ =(1-r)·M λbb

[0083] Where r is the spectral reflectance of the object.

[0084] 33) Calculate the spectral radiance M of the object in a certain spectral band according to the spectral spontaneous radiation of the object λ～λ+Δλ .

[0085] Specifically, due to the need to calculate the spectral band radiation, the spectral radiation values ​​in this embodiment are all pseudo spectral radiation values, which are the integral of the spectral radiation values ​​on the subdivided spectral bands. Then:

[0086]

[0087] Among them, M λ～λ+Δλ It represents the spectral radiance in the spectral range of λ~λ+Δλ, that is, the radiance of discrete spectral ranges, Δλ represents the spectral subdivision degree, and in this embodiment, dλ'=Δλ / 100000.

[0088] Step 4: Calculate the spectral radiance of the scene based on the view factor and the spectral radiance of the object.

[0089] In this embodiment, after obtaining the spontaneous radiation of the objects in the scene, that is, the spectral radiance of the objects, the irradiance is calculated according to the angular coefficients between the facets, and then the direct illumination of each discrete spectral segment plus multiple indirect illumination calculations are performed and accumulated to obtain the scene spectral radiance of the spectral segment.

[0090] Specifically, step 4 includes:

[0091] 41) According to the reciprocity theorem of angular coefficients, the angular coefficient of the source patch to the target patch is converted into the angular coefficient of the target patch to the source patch;

[0092] Among them, the reciprocity theorem of angular coefficients is expressed as:

[0093] A1F 12 =A2F 21

[0094] Then there is

[0095]

[0096] Where A1 and A2 represent the areas of source patch 1 and target patch 1 respectively, and F 12 Indicates the angular coefficient of source patch 1 to target patch 2, F 21 Represents the angular coefficient of target patch 2 to source patch 1.

[0097] 42) Calculate the spectral radiance emitted by the target patch under single reflection based on the angular coefficient of the target patch to the source patch

[0098] Specifically, considering only a single reflection (direct illumination), the spectral radiation power emitted by the target surface is:

[0099] P λ =E λ ·A+r∑F 12 E' λ ·A'

[0100] Where r is the reflectivity of the target surface; E λ , A, E' λ , A' are the spectral spontaneous radiation and area of ​​the target patch and other source patches in the scene, respectively.

[0101] Dividing both sides of the above equation by A, we get the spectral radiance emitted by the target patch:

[0102]

[0103] According to the reciprocity theorem of angular coefficients, we have

[0104]

[0105] 43) According to the spectral radiance emitted by the target patch in the case of single reflection Calculate the spectral radiance emitted by the target patch under two reflections

[0106] Specifically, considering two reflections (direct light plus one indirect light), we have

[0107]

[0108] in, is the direct illumination spectral radiance of the source patch, and

[0109] 44) Iterate the calculation until the scene is saturated, and obtain the spectral radiance emitted by the target patch under n reflections

[0110] Specifically, considering n reflections (direct illumination and n-1 indirect illumination), then

[0111]

[0112] Where n≥3, represents the spectral radiance of the source patch after n-1 radiation reflections, and

[0113] It can be seen from the above formula that the process from one reflection to multiple reflections is an iterative operation process, and the result of the previous operation is used as a variable to obtain the result of this operation.

[0114] The above iterative formula is used to calculate through multiple reflections until the scene spectral radiance is saturated.

[0115] In this embodiment, it is generally considered that if the increment of a certain iteration result over the previous result does not exceed 0.1%, the scene is considered to have been iteratively converged.

[0116] In addition, the iterative calculation can be ended by setting the maximum number of iterations (i.e., the number of reflections n). Through testing, scenes with less than 10,000 triangles generally converge within 20 iterations. Based on this, 32 reflection iterations are generally set. Obviously, when the increment of a certain iteration result over the previous result does not exceed 0.1%, the iteration can be ended early.

[0117] 45) Integrate the obtained spectral radiances over a certain spectrum segment to obtain the spectral radiance of the scene in the current spectrum segment. The formula is expressed as:

[0118]

[0119] The present invention realizes the quantitative calculation of infrared multi-radiation source coupling transmission by using a radiometry algorithm, and can output the radiance distribution of scenes in different spectral bands in the form of images. Since the adopted radiometry algorithm has simple theory and simple scenes, the method of the present invention is light and easy to implement.

[0120] Since the algorithm itself treats all objects as light sources and renders the entire scene, the simulation result includes all objects in the scene, and switching the viewing angle does not require recalculation. For complex static scenes, when the relative positions of objects in the scene remain unchanged, the geometric relationship (angle coefficient) between the objects only needs to be calculated once, and can be used for any subsequent radiation calculation without repeatedly calculating the angle coefficient, which greatly saves time costs. Therefore, the method of the present invention does not require a large number of sampling of light sources and light for scenes with multiple radiation sources, and the calculation rate is faster.

[0121] In addition, the present invention is based on the physical radiation law and starts from the temperature and reflectivity of the object to calculate the spectral spontaneous radiation of the object, and the calculation result has high authenticity and credibility.

[0122] 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 quantitative calculation method for infrared multi-radiation source coupled transmission, characterized in that: include: Step 1: Obtain three-dimensional scene information and divide the scene into a number of triangular facets; Step 2: Calculate the angular coefficients between each triangular face; 21) For a certain triangle in the scene, it is regarded as the target patch, and the other triangles in the scene are regarded as source patches; 22) Based on the semi-cube algorithm, the OpenGL rendering technology is used to project the visible area of ​​a source patch to the target patch on the semi-cube at the center and normal side of the target patch, and obtain several micro-element patches corresponding to the current source patch; 23) According to the solid angle projection theorem, the angle coefficient of each micro-element of the current source patch to the target patch is calculated by the projection area; wherein the calculation formula of the angle coefficient is: Among them, dF 12 It represents the angular coefficient of a microelement of source patch 1 to target patch 2. θ1 and θ2 are the angles between the center line of the two patches and the normal lines of the two patches, respectively. 12 is the distance between the two patches, A2 is the area of ​​target patch 2; 24) Accumulating the angular coefficients of all micro-element patches of the current source patch to the target patch to obtain the angular coefficient of the current source patch to the target patch; 25) Repeat steps 22)-24) to obtain the angular coefficients of all source patches to the target patch; Step 3: Calculate the spectral radiance of objects in the scene; 31) Calculate the blackbody spectrum spontaneous radiation M of the object temperature λbb , the calculation formula is as follows: Where c1 represents Planck's first radiation constant, c2 represents Planck's second radiation constant, λ represents the current spectrum wavelength, and T represents the absolute temperature of the black body; 32) Calculate the spectral spontaneous radiation M of the object according to the black body spectral spontaneous radiation of the object temperature λ , the calculation formula is as follows: M λ =(1-r)·M λbb Where r is the spectral reflectance of the object; 33) Calculate the spectral radiance M of the object in a certain spectral band according to the spectral spontaneous radiation of the object λ～λ+Δλ , the calculation formula is as follows: Among them, Δλ represents the spectral subdivision; Step 4: Calculate the spectral radiance of the scene according to the angular coefficient and the spectral radiance of the object.

2. The quantitative calculation method of infrared multi-radiation source coupled transmission according to claim 1 is characterized in that: Before calculating the spectral radiance of objects in the scene in step 3, it also includes: Determine the spectral bands to be calculated and the spectral band subdivision level.

3. The quantitative calculation method of infrared multi-radiation source coupled transmission according to claim 1 is characterized in that: Step 4 includes: 41) According to the reciprocity theorem of angular coefficients, the angular coefficient of the source patch to the target patch is converted into the angular coefficient of the target patch to the source patch; 42) Calculate the spectral radiance emitted by the target patch under single reflection based on the angular coefficient of the target patch to the source patch The calculation formula is as follows: Among them, E λ represents the spectral spontaneous radiation of the target patch, F 21 Indicates the angular coefficient of target patch 2 to source patch 1, E' λ represents the spectral spontaneous radiation of the source patch, and r is the spectral reflectivity of the object; 43) According to the spectral radiance emitted by the target patch in the case of single reflection Calculate the spectral radiance emitted by the target patch under two reflections The calculation formula is as follows: in, is the direct illumination spectral radiance of the source patch, and 44) Iterate the calculation until the scene is saturated, and obtain the spectral radiance emitted by the target patch under n reflections The calculation formula is as follows: Where n≥3, represents the spectral radiance of the source patch after n-1 radiation reflections, and 45) Integrate the obtained spectral radiances over a certain spectrum segment to obtain the spectral radiance of the scene in the current spectrum segment. The formula is expressed as: Among them, Δλ represents the spectral subdivision.

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