CN108829906A - A kind of rescattering calculation method of complex target to background light radiation - Google Patents
A kind of rescattering calculation method of complex target to background light radiation Download PDFInfo
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- G01S13/006—Theoretical aspects
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
The present invention provides a kind of complex targets to the rescattering calculation method of background light radiation, solves the problems, such as that scattering area calculates between the judgement of rescattering, face element pair between complex target face element pair and the rescattering of complex target calculates.It is embodied as：Establish object module；It inputs the MOD model information of built target and carries out blocking processing；Judged for the first time rescattering is carried out between the target face element pair that blocks that treated；Conversion coordinate system simultaneously calculates the scattering area between face element pair；Complete the rescattering of complex target.The present invention first finds out the face element pair that rescattering may occur, by conversion coordinate by the face element in space to project to conversion coordinate system XOY plane in, two dimension is converted by three-dimensional problem, simplify operation, reduce program complexity, the rescattering brightness between face element pair, and entire rescattering brightness of the complex target to background light radiation, the accurate detection for sea, space and ground complex target are acquired using BRDF by obtained scattering area.
Description
Technical field
The invention belongs to light of the target in complex background to background radiation to scatter field, relate generally to spatial complex target and build
The optical radiation of mould, background calculates, and single and secondary light scattering differentiate and calculate that calculated result can be applied between target plate
Scattering properties calculating, the tracking of target and the identification etc. of target in sea, space.
Background technique
Complex target complicated mesh in the backgrounds such as sea, the sun, sky to the rescattering calculation method of background light radiation
There is important application value in the detection of target optical information, recognition and tracking.Complex target radiates various background opticals
Scattering properties calculating is the important means of goal in research characteristic, is the important component of complex target optical characteristics detection, grinds
Complex target is studied carefully to the rescattering characteristic of background radiation, provides more accurate calculated result for target property calculating.
It is mostly currently the research to radar scattering interface (RCS) to the research of target rescattering.And since target is to two
Secondary scattering RCS's estimates with target to the difference existed on the sun, sky and the optical region on sea rescattering algorithm fundamentally
It is different, so can only propose specific method in calculating target studies the sun, sky and the rescattering on sea.
When carrying out target the research of rescattering, need individually to calculate target.In " light scattering of object characteristic
In biggest advantage of light track algorithm research and realization in a calculating " text, Wu Kaifeng et al. gives to compare using the thought of ray tracing to be had
The ray-test calculation method of effect, and applied to using the test method in complex target light scattering characteristic theoretical modeling, and
Give the light scattering luminance graph of rescattering effect of the complex target under solar irradiation.But the algorithm does not provide specifically
Calculate face element pair between scattering area calculating.In " the high frequency mixed method research that complex target Multiple Scattering a calculates " text
In, Zhao Weijiang et al. is derived one kind on the basis of method of geometrical optics, in conjunction with method of geometrical optics and ray-tracing procedure
Method-region projection physical optical method of complex target Multiple Scattering can be effectively calculated, this method can effectively calculate face element
The scattering area size between, and relatively good precision can be obtained to target RCS calculating, but this method is calculating scattering surface
When product, method of geometry used is not intuitive enough, and programming is realized more complicated.And this method is to be specifically applied to target to radar
Rescattering calculate, therefore when calculating complex target to the rescattering of background, judge rescattering occurrence condition with
And reference value is provided only by when calculating scattering area, it is also necessary to which new algorithm calculates target to the two of the sun, sky and sea
Secondary scattering.
Summary of the invention
It is secondary in view of the deficiencies of the prior art, the present invention provides the complex target that a kind of complexity is low, is easily programmed
Scatter calculation method.
The present invention is a kind of rescattering calculation method of complex target to background light radiation, which is characterized in that includes
Following steps：
Step 1：Establish object module：The 3dmax model of target is established by 3dmax, then by the 3dmax mesh of foundation
Mark model conversion is MOD model；MOD model divides quinquepartite to form, first part be model format identification information, face element number and
Number of vertex；Second part is face element index value, component index value, material index value, color index value and vertex index values；Third
Part is the coordinate value of vertex index and point；Part IV is component index value and unit type title；Part V is material
Index value and Material Name.
Step 2：Input the MOD model information of target：Model is carried out from processing is blocked, so first with method of geometry
Afterwards for from all face elements in the target MOD model that blocks that treated, blocking between face element is utilized into Z-BUFFER blanking
Algorithm process, Z-BUFFER efficient rendering algorithm by by incident direction or scattering direction be Z axis establish Descartes's three-dimensional system of coordinate,
Target MOD model projection is divided into several pictures into this coordinate system, the target MOD model after projection in XOY plane
Element, the number of pixel should be much larger than the face element number of model and save all pixels according to the location information of pixel in a coordinate system
In the Pixel Information do not blocked by other pixels, it is all that target MOD model can be obtained finally by the Pixel Information of preservation
The face element size that each face element is not blocked in face element thinks this face if the area that face element is blocked is less than half
Member is not blocked, otherwise it is assumed that face element is blocked；Finally removed in target MOD model it is all block face element, obtain not by
The target MOD model blocked；
The rescattering under background light radiation is carried out to the target MOD model face element not being blocked to calculate；
Step 3：Rescattering judges for the first time between target face element pair：To all face elements of target MOD model not being blocked
Traversal is successively judged as between initial face element, that is, face element 1 and remaining face element, and rescattering if possible occurs, then this two
A face element forms a face element pair, executes step 4, carries out coordinate system conversion, and calculates secondary scattered between this face element pair
It penetrates, step 3 is repeated if rescattering does not occur, the rescattering carried out between next face element pair judges for the first time；
Step 4：Coordinate system conversion：For using the sun as incident light, rescattering of the target to the sun is calculated, is led to
It crosses sun incident direction and the mirror image scattering direction that solar irradiation is mapped on face element 1 is calculated, built using mirror image scattering direction as Z axis
New coordinate system is found, which is defined as S coordinate system, S coordinate system remains as Descartes's three-dimensional system of coordinate, face element to throwing
In shadow to the XOY plane of S coordinate system；
Step 5：Calculate the scattering area between face element pair：In the S coordinate system that step 4 is established, thrown in X0Y plane
Positional relationship between shadow face element has intersection, separation and comprising saving all intersection points between face element line segment and including mutually
Point, then removal repeats point, if the number of remaining point less than 3, proves that closed area cannot be formed, i.e., cannot occur two
Secondary scattering；Otherwise the smallest point of Y value is found out to remaining each point and is set as MinP, successively calculate of other each points relative to MinP
Angle size is ranked up each point according to subtended angle size, finally carries out area of a polygon calculating to sorted point；
Step 6：The rescattering for calculating and completing complex target to background light radiation：According to bidirectional reflectance distribution function
(BRDF) the mirror image scattering brightness size found out on face element 1 obtains face element by the transformational relation between spoke brightness and irradiation level
2 irradiation level received, the intersecting area size then found out according to step 5 find out face element dissipating to upper face element 1 and face element 2
Size is penetrated, finally according to the bidirectional reflectance distribution function (BRDF) on face element 2, the rescattering between face element is counted
It calculates, and then the rescattering for completing complex target calculates.
Can the present invention calculate rescattering face element and dissipate by judging that rescattering occur between complex target face element pair
The area penetrated is realized and is calculated the rescattering of background light radiation complex target.
Compared with prior art, advantages of the present invention：
1. complexity is low：When calculating rescattering between face element pair, relatively difficult place is how to calculate face element
Between scattering area size.The calculating of scattering area is proposed when the present invention calculates the rescattering of complex target a kind of multiple
The miscellaneous lower algorithm of degree.Direction is scattered as z-axis by the mirror image of a face element and establishes a new coordinate system, will occur two
The face element of secondary scattering is to projecting in new coordinate system, by judging the positional relationships of two projection face elements there is intersection, include
Point save；By finding out the smallest point of wherein y value in the point of preservation, then calculates remaining each point and this point is opened
Angle size is simultaneously ranked up, and calculates its area of a polygon surrounded to the point for taking sequence, and then complete a face element to upper face element
Between rescattering brightness.Finally to all face elements to calculating, the rescattering size of entire target is obtained.
2. being easily programmed：The present invention has the characteristics that be easily programmed, in the process for calculating complex target rescattering calculating
In, the problem of needing to calculate the scattering area size between face element pair, be directed to polygon intersection, in the present invention, to scattered
The calculating for penetrating size only need with simple programming language it is achieved that and in calculating process to energy between face element
Judgement has also been made in no generation rescattering, and method is easy-to-understand, is easier programming and realizes.It is no matter secondary in calculating sea-surface target
Scattering still in the rescattering of extraterrestrial target, can realize mesh using eaily programming language according to this method
Mark the calculating of the rescattering to background light radiation.
Detailed description of the invention
Fig. 1 is the flow chart of the method for the present invention；
The first judgment models schematic diagram of Fig. 2 face element rescattering；
Fig. 3 face element is to intersection schematic diagram；
Fig. 4 face element is to including schematic diagram；
Fig. 5 is subtended angle figure of each point relative to MinP point；
Fig. 6 face element is to rescattering schematic diagram；
Fig. 7 is calculated examples model of the present invention；
Fig. 8 is the aluminium nest bee material BRDF model used when the present invention calculates；
When Fig. 9 is that the present invention calculates, it is seen that the solar spectrum irradiancy under the conditions of light, at 45 degree of solar zenith angle；
Figure 10 is the scattering brightness using present invention target calculated to solar radiation, respectively calculates secondary dissipate
The scattering brightness penetrated and the scattering brightness for not calculating rescattering.
Specific embodiment
Embodiment 1
When the rescattering to complex target calculates, someone utilizes region projection physical optical method in the prior art
The rescattering for calculating complex target, although the size of scattering area can be calculated effectively, when programming realization
It is more complicated, and the method is to be exclusively used in calculating radar cross section (RCS), for meter of the complex target under different background
Calculate no universal significance.The present invention proposes a kind of complex target in sunlight, sky and sea light after study regarding to the issue above
Rescattering calculation method under radiation background includes following steps referring to Fig. 1：
Step 1：Establish complex target model：The 3dmax model that target is established by 3dmax, then by foundation
3dmax object module exports the file that format is 3DS, is revised as files classes used in the present invention by derived 3DS file
Type is the object module of MOD, and target MOD model face element type is Triangular object model；MOD model divides quinquepartite to form, and first
It is divided into model identification information, face element number and number of vertex；Second part is face element index value, component index value, material index value, color
The index value of color index value and vertex；Part III is the coordinate value of vertex index and point, corresponding three seats of a vertex index
Scale value；Part IV is component index value and unit type title；Part V is material index value and Material Name.After modification
The MOD file model information content it is simpler, can the relatively clear face element number and number of vertex that intuitively find out model, compiling
When journey reads the face element information and vertex information of file, it is more easier programming and realizes.When the interface using OpenGL implementation model
When change, pass through established MOD model, it is easier to adjust model according to their own needs, the reading file that can be more easier
Information, so the present invention takes the model of MOD file type to calculate, as shown in fig. 7, Fig. 7 is one used in the present invention
Example model, model are made of the square that one 10 meters of side length of square plate and a side length is 2.5 meters, this is square
Body is located at the center of plate, and square up and down two bottom surfaces while with plate while it is parallel, in order to make it easy to understand, figure
In direction received to sun incident direction and detector all done apparent mark, sun incident direction is in direction model in figure
The heart is biased to 45 degree of directions of X-axis for Z axis, and detector direction is from Z axis along clockwise to X-axis.Complexity mesh of the present invention
Mark is a three-dimensional model, the three-dimensional complex target that it is made of thousands of a face elements, in calculating process, is needed pair
All face elements of model are calculated.In described below, such as non-specified otherwise, the target being previously mentioned refer both to complex target.
Step 2：Input the MOD model information of target：In the MOD model of foundation, first with method of geometry to MOD
Model carries out external from processing is blocked, and blocking processing certainly is sentenced using the corner dimension of incident direction opposite direction and face element normal
Whether section member is blocked by itself, if angle is greater than 90 degree, then it is assumed that face element is blocked by itself, if angle is less than 90 degree
Think that face element is not blocked by itself, and for the occlusion issue between complex target face element, simple method of geometry then cannot
It judges soundly.Because a face element of complex target may be blocked in an incident direction by other face elements, but this
A face element being blocked meets geometrical relationship therefore can not be judged as blocking, so for after method of geometry blanking
The mutual occlusion issue between face element can not be eliminated in target MOD model, the present invention utilizes Z-BUFFER efficient rendering algorithm process face
First the problem of blocking mutually.The basic principle of Z-BUFFER efficient rendering algorithm is：It is new coordinate by incident direction or scattering direction
The Z axis of system establishes Descartes's three-dimensional system of coordinate, and using Z axis in naval vessel coordinate system the XOY plane of new coordinate system projection as
The Y-axis of new coordinate system, that is, the new coordinate system established based on Z-BUFFER algorithm.The present invention arrives target MOD model projection
In this new coordinate system, then the target MOD model after this projection is an areal model in the XOY plane of new coordinate system,
This areal model is divided into several pixels in XOY plane, the number of pixel should be much larger than the face of target MOD model
First number, according to pixel in new coordinate system location information, save the Pixel Information do not blocked by other pixels in all pixels, most
Each face element can be obtained in target MOD model in naval vessel coordinate system not by other face elements by the Pixel Information saved afterwards
The face element size blocked.Think that this face element is not hidden if the area that face element is blocked is less than half in the present invention
Gear, else if the area that face element is blocked, which is greater than or equal to half, thinks that face element is blocked.Finally in target MOD model
Except all block face element, the target MOD model that complex target is not blocked is obtained.
Rescattering calculating is carried out to the target MOD model not being blocked；
Step 3：Rescattering judges for the first time between target face element pair：To all face elements of target MOD model not being blocked
It traverses and is successively judged as initial face element, that is, face element 1 and remaining face element, as shown in Fig. 2, 1 center of face element is into face element 2
The direction vector of the heart isIf then can be seen that direction vector from the positional relationship of face element 1 and face element 2With 1 normal of face element
The angle in direction is less than 90 degree and direction vectorWhen being greater than 90 degree with the angle of face element 2, then it is assumed that can between the two face elements
Rescattering can occur, the two face elements are formed a face element pair, execute step 4, carry out coordinate system conversion, and calculate this
Rescattering between a face element pair, face element is to including face element 1 and face element 2；Step is repeated if rescattering does not occur
Rapid three, the rescattering for carrying out next face element pair judges for the first time.
Step 4：Coordinate system conversion：For using sunlight as incident light, rescattering of the target to the sun is calculated,
The mirror image that solar irradiation is mapped on face element 1 is calculated by sun incident direction and scatters direction, using mirror image scattering direction as Z axis
New coordinate system is established, which is named as S coordinate system, throwing of the Z axis in S coordinate system XOY plane in naval vessel coordinate system
Shadow is the Y-axis of new coordinate system, which remains as Descartes's three-dimensional system of coordinate, face element to the XOY for projecting to S coordinate system
In plane, compared with former coordinate system, the purpose for establishing S coordinate system is to calculate the scattering area of face element pair for convenience, because of mesh
Mark model is that three-dimensional model compares so needing to calculate the scattering area of two face elements in space if not establishing S coordinate system
Complexity, and the present invention face element to projecting in S coordinate system when, it is only necessary to calculate in S coordinate system project face element in XOY
Intersecting area size in plane, then dissipating for face element centering face element 1 and face element 2 can be calculated by coordinate system inverse transformation
Size is penetrated, calculating process is enormously simplified, programming is also easy to and realizes.
Step 5：Calculate the scattering area between face element pair：In S coordinate system, face element is projected to the position in lower X0Y plane
The relationship of setting have intersection, separation and comprising.Fig. 3 is face element to intersection schematic diagram, as shown in figure 3, face element 1 is in S coordinate system XOY plane
Interior projection face element is face element 11, projection face element of the face element 2 in S coordinate system XOY plane is face element 21, face element 11Three
Side is successively to face element 21Three sides carry out intersection testing, save the point of intersection.If two line segments have weight in calculating process
Close part, using two points of intersection as by comprising point.No intersection point is thought if two lines section is non-intersecting.Fig. 4
It is face element to mutually completely including schematic diagram, face element is to the projection face element in S coordinate system XOY plane to for face element 11And face element
21, according to Fig. 4 as can be seen that face element 21It is completely contained in face element 11It is interior, then by comprising vertex have altogether there are three, then this
The coordinate of three points all saves.Comprising being divided into all comprising including with part, if the part vertex of a face element of target exists
Also belong to the case where including in another face element, it is all by comprising apex coordinate save.If projecting face element in S coordinate
Then without crosspoint if being separated from each other in XOY plane in system.It saves all intersection points between face element line segment and includes mutually
Vertex simultaneously removes repetition point, if the number for saving point less than 3, proves that the point saved cannot form closed area, i.e., cannot
Rescattering occurs, returns to step 3, continues rescattering between the next face element pair of target and judge for the first time.Otherwise,
If the number for saving point is more than or equal to 3, the smallest point of Y value in XOY plane is found out in S coordinate system in the point of preservation and is set
For MinP, subtended angle size of other each points relative to MinP point is successively calculated, successively each point is arranged according to subtended angle size
Sequence finally carries out area of a polygon calculating to sorted point.
Step 6：The rescattering for calculating and completing complex target to background light radiation：According to bidirectional reflectance distribution function
(BRDF) mirror image scattering brightness size of the sunlight on face element 1 is found out, by the transformational relation between spoke brightness and irradiation level,
The spectral irradiance received on face element 2 is obtained, then according in the intersecting area size and S coordinate system acquired in step 5
Z axis and face element find out the scattering area size in face element to upper face element 1 and face element 2, last root to the corner dimension of two face elements
According to the bidirectional reflectance distribution function (BRDF) on face element 2, face element centering face element 1 calculates the rescattering of face element 2, into
And the rescattering for completing complex target calculates.The present invention be using sunlight as radiation source for calculate, sunlight
Incident direction is single, is easier to calculate, and calculated result as shown in Figure 10 is that target calculates two under solar radiation
The brightness value of secondary scattering and a comparison diagram for not calculating rescattering brightness value.
Goal in research of the present invention equally has feasibility when calculating the rescattering of sky background and Sea background, only needs
Face element calculate all in accordance with the above method in each direction and is integrated to institute is angled.With Ship Target
For calculating the rescattering of background light radiation, naval vessel is not only by solar radiation also simultaneously by sky background light radiation
With Sea background light radiation, when calculating rescattering of the naval vessel to solar radiation, since sun incident direction is single, letter is calculated
It is single, target can be completed according to above-mentioned routine, the rescattering of solar radiation is calculated；Target is being calculated to sky and ocean background light
When the rescattering of radiation, need to calculate each direction in space, target face element can receive sea in space
The direction one of its background light radiation shares 180x360, when calculating rescattering calculating of the target to sky and ocean background light radiation,
It needs to calculate each direction.When calculating rescattering of the target to sky and ocean background light radiation, target face element is simultaneously
Sea background light radiation and sky background light radiation are received, judge that face element receives in one direction when calculating is day
Empty background light radiation or Sea background light radiation are distinguished as follows, i.e., if incidence of the incident light under naval vessel coordinate system
What angle then thought that this face element receives less than 90 degree is sky background radiation, if incidence of the incident light under naval vessel coordinate system
Angle is greater than 90 degree, and then think that this face element receives is that Sea background radiates, each side finally received to target face element
It is calculated to the incident direction as above-mentioned routine, finally carries out integral summation, so that it may show that complex target carries on the back extra large day
The rescattering brightness of scape light radiation.So the rescattering calculating of target sky and ocean background light radiation and target are too when calculating
The difference that rescattering under positive background light radiation calculates is exactly, sky and Sea background radiation to the rescattering of target be by
Each direction that face element can receive is calculated as incident direction, and target is secondary under sun background light radiation
Scattering is only needed using sunlight direction of illumination as incident direction.So this method is to calculating complex target to Sea background
Light radiation and sky background light radiation equally have feasibility.This method is equal to the rescattering for calculating aircraft, satellite, vehicle etc.
Engineering application value with higher.
When calculating complex target rescattering, relatively difficult place is how to calculate scattering area between face element pair
Size.The invention proposes a kind of new algorithms of scattering area between calculating face element, and complexity is low, is easily programmed.Pass through one
A new coordinate system as z-axis is established in the mirror image scattering direction of a face element, and the face element of rescattering will occur to projecting to
In new coordinate system, by judging that the positional relationship of two projection face elements saves the point that there is intersection, include；Lead in the point of preservation
It crosses and finds out the smallest point of wherein y value, then calculate remaining each point and the subtended angle size of this point is ranked up, then count
The area for calculating polygon, finally finds out face element to the scattering area size of upper face element 1 and face element 2 according to coordinate system inverse transformation.
The present invention proposes a kind of more effective algorithm to the rescattering of the sun for target, therefore also answers with engineering
With value.
Embodiment 2
The rescattering calculation method of complex target with embodiment 1, coordinate system described in step 4 conversion include with
Lower step：
4.1 set sun incident direction asThen incident rayWith the normal of face element 1It can be asked using following geometric formula
Obtain incident ray directionMirror reflection direction on face element 1
4.2 with reflection directionZ as new coordinate1Axis, new coordinate system x1o1y1Plane is vertical with back wave direction, y1Axis
The z-axis of naval vessel coordinate system is taken as in x1o1z1Projection in plane, new coordinate system are previously mentioned S coordinate system, naval vessel coordinate
System and S coordinate system transformational relation are as follows：
Wherein θ is incidence angle of the sunlight incident direction on ground naval vessel coordinate system,Subtracting for sunlight incident direction
Produce the azimuth on coordinate system, o1x1y1z1Indicate that S coordinate system, oxyz are naval vessel coordinate system,For x in S coordinate system1Axis direction,For the y of S coordinate system1Axis direction,For the z of S coordinate system1Axis direction.
The purpose that the present invention converts coordinate system is in order to which the scattering area of two triangles in calculating three-dimensional coordinate is converted
For the intersecting area for calculating two triangles under two-dimensional surface, calculating process is simplified.The present invention is scattered with the mirror image on face element 1
Direction is that Z axis establishes S coordinate system, and Z axis is projected as Y-axis in XOY plane in S coordinate system in naval vessel coordinate system, it is therefore an objective to be
The face element calculated can be made to be kept upright in new coordinate system, and can easily calculate face element under S coordinate system
x1o1y1Intersecting area in plane, finally to calculate the rescattering of target, so the present invention devises coordinate change
It changes and complex target rescattering is calculated, so that entire calculating process is relatively easy sequencing and realize and calculate.
Embodiment 3
The rescattering calculation method of complex target calculates face element under S coordinate system described in step 5 with embodiment 1
Scattering area between, including have the following steps：
5.1 can occur projection face element of the face element of rescattering to face element 1 and face element 2 in S coordinate system in XOY plane
Respectively face element 11With face element 21, the two projection face elements between relationship in S coordinate system in XOY plane there are three types of：Intersection,
Include and separates.Intersection refers to whether intersect between projection face element opposite side and side, referring to Fig. 3.Comprising referring to projection face element to two
Whether a vertex of a triangle is by comprising referring to fig. 4.And separating then is projection face element to not having any intersection point under S coordinate system
With comprising point, so only being needed when calculating scattering area to intersection and being discussed comprising two kinds of situations.
5.2 by face element 11With face element 21Three sides under S coordinate system in XOY plane successively carry out intersection testing, if there is
Crosspoint then saves the coordinate of crosspoint, as shown in figure 3, by face element 11Three sides to face element 21Three sides successively asked
Test is handed over, then significantly sees that there are four intersection points from figure, so four intersection points are saved.If in the judgment process, occurred
There is the part of coincidence on two sides determined, then two points of intersection as including a processing.If it is determined that two sides
Determined not intersect, then it is assumed that this two sides do not have crosspoint.
5.3 judge face element 11With face element 21With the presence or absence of mutual the case where including, such as Fig. 4 in XOY plane under S coordinate system
It is shown, face element 21Completely by face element 11Include, so these three points are saved.The present invention judges face element to the method for mutually including
It is successively to judge in S coordinate system face element 1 in XOY plane1Three vertex whether in face element 21It is interior, face element 2 is then judged again1's
Whether three vertex are in face element 11It is interior.To judge face element 11Three vertex whether in face element 21For interior, face element 1 is successively selected1
Three vertex as vertex to be judged, this participates in the vertex of judgement and face element 21Three vertex can form three three
It is angular, if this participates in the vertex of judgement in face element 21It is interior, then the area of these three triangles and with face element 21Size
It is equal.If face element 11The vertex of judgement is participated in face element 21The area for three triangles being divided into and with face element 21Area not phase
Deng then proving face element 11The vertex of judgement is participated in not in face element 21It is interior, successively to face element 11Three vertex carry out above-mentioned judgement,
All qualified points are saved, then successively judge face element 2 according to the method described above1Three vertex whether in face element 11It is interior, so
All qualified points are saved afterwards.
The point coordinate of 5.4 pairs of all preservations carries out duplicate checking processing, deletes the identical point of XY coordinate value in the point coordinate of preservation,
Specific method is if the X-coordinate value difference absolute value of two points is no more than 10-4And Y-coordinate value difference absolute value is no more than 10-4
Being considered as two coordinates is to be overlapped, if the number of left point is less than 3 after deletion repetition point, the two Triangular object models are not
Rescattering can occur, execute step 3, the rescattering for carrying out next face element pair judges for the first time.Otherwise, that is, it deletes and repeats
The number of left point thinks that rescattering can occur for the two face elements more than or equal to 3 after point, step 5.5 is executed, to preservation
Point is ranked up.
The point of 5.5 pairs of preservations is ranked up：Y value is projected under S coordinate system in XOY plane most to finding out in each point of preservation
Small point is set as MinP, as shown in figure 5, four in Fig. 5 point and MinP point are the points saved in step 5.4, then according to this
Four points are successively ranked up relative to the subtended angle size of MinP point, the point after just obtaining in figure four sequences, that is, put 1, point 2,
Point 3, point 4.Point 1, point 2, point 3 and point 4 are sequentially increased relative to the subtended angle of MinP, are sorted so saving again according to this sequence
Each point afterwards finally saves MinP point, and each point for being sequentially connected preservation forms a polygon that can be calculated.
The each point of 5.6 pairs of all preservations carries out area of a polygon calculating：The polygon that each point is formed will be saved and regard several as
The sum of a triangle area is calculated, it is assumed that and the number of the point of preservation is n (n >=3), this n number consecutivelies from 1 to n,
Then this n point composition polygon n-2 triangle is combined into according to following combination, i.e., point (1,2,3), point (1,3,
4) ... point (1, n-1, n), as soon as each bracket indicate a triangle, so area of a polygon and be this n-2 triangle
The sum of area.It acquires according to the method described above and saves the area of a polygon size that each point surrounds, finally utilize S coordinate system Z axis and warship
Angle between two face elements of face element pair in ship coordinate system, acquires face element to the scattering area of upper two face elements.
Embodiment 4
The rescattering calculation method of complex target is with calculating described in 1 step 6 of embodiment and completes complex target
Rescattering includes following steps：
6.1 scatter direction and sun incident direction according to the mirror image on the face element 1 acquired in step 4.1, find out the sun and enter
Incidence angle and azimuth of the direction on face element 1 are penetrated, mirror image scatters angle of scattering and azimuth of the direction on face element 1.The present invention
BRDF model used is five-parameter model, by incidence angle of the sunlight on face element 1 and azimuth, is found out on face element 1
Scattering brightness on any scattering direction, therefore the scattering of the mirror image on face element 1 brightness L is acquired according to BRDFi：
Li=f1Esun(λ)cosθi
F in formula1For the BRDF size of face element 1, Esun(λ) is the corresponding solar irradiance of fixed wave length, θiFor sunlight
The angle of incident ray and 1 normal of face element.
6.2 according to the intersecting area size and S coordinate system Z axis and face element centering face element acquired in XOY plane in S coordinate system
Corner dimension between 1 and face element 2 finds out the scattering area size of face element 1 and face element 2 in face element pair：The scattering surface of face element 1
Product is S1, the scattering area of face element 2 is S2。
Conversion between 6.3 spoke brightness and irradiation level：As shown in fig. 6,1 scattering area S of face element1It issues and falls on face element 2
Scattering area S2On radiation flux Φ be：
Φ=LicosθrS1Ω
θ in formularFor the angle of face element 1 normal and two face element lines of centres, Ω is 2 scattering area S of face element2Face element 1 is dissipated
Penetrate area S1The solid angle opened, i.e.,The distance at 2 center of face element 1 and face element is R, θdFor 2 normal of face element with
The angle of two face element lines, then 1 scattering area S of face element1In 2 scattering area S of face element2The spectral irradiance E (λ) of upper generation is：
E (λ)=f1Esun(λ)cosθi·cosθr·cosθd·S1/R2
6.4 can acquire face element 1 to the rescattering brightness dL of face element 2 using the BRDF on face element 2r：
dLr=f2(f1Esun(λ)cosθi)S2cosθscosθrcosθddλ/R2
Complex target finally can be obtained to the rescattering brightness L of the sun using formula as abover,
The calculating of the rescattering of complex target is completed, wherein n indicates all face element logarithms that rescattering can occur.
The present invention proposes a kind of algorithm on the basis of having studied the condition of target rescattering formation, decision rule
It realizes the judgement that target surface can occur the face element pair of rescattering, calculates the effective area for generating rescattering face element,
And it is finally completed the calculating of complex target rescattering.
Light scattering of object characteristic research is one of important component of target optical characteristic, complex target light scattering characteristic
Key point and difficult point in calculating are the hiding relations and Multiple Scattering problem solved between target difference component.It is calculating
When complex target rescattering, it is necessary first to the face element of rescattering can occur to judging to target, finding out can send out
The dihedral angle structure of raw rescattering obtains face element to it by finding out the face element that rescattering can occur to calculating
Between rescattering, and then calculate the rescattering brightness of entire target.The calculating of rescattering is to the accurate of target detection
Estimate important application value.It finds out the face element pair that rescattering may occur first in the present invention, calculates for convenience
Scattering area between face element pair, conversion coordinate system to projecting in the XOY plane of conversion coordinate system, incite somebody to action the face element in space
Three-dimensional problem is converted into two-dimensional problems and simplifies calculating process, reduces the complexity of program, scattering surface obtained by calculation
Product can be in the hope of the rescattering brightness between face element pair using BRDF, and then obtains the rescattering brightness of entire target.
Therefore the present invention has many advantages, such as that complexity is low, is easily programmed when calculating the rescattering of complex target, is suitable on sea
The accurate detection of target, extraterrestrial target and ground target, engineering application value with higher.
A more full and accurate example is given below, the present invention is further described
Embodiment 5
The rescattering calculation method of complex target with embodiment 1-4,
In the following description, numerous specific details are set forth in order to facilitate a full understanding of the present invention, but the present invention can be with
It is different from the other methods of this description using other to implement, those skilled in the art can be in the feelings without prejudice to intension of the present invention
Similar popularization is done under condition, therefore the present invention is not limited by following public specific example.
Fig. 1 is the flow chart of invention.Referring to Fig.1, the calculation method of complex target rescattering of the present invention includes following step
Suddenly：
Step 1：Establish complex target model：The 3dmax model that target is established by 3dmax, then exports as model
3DS model modification is reduced to MOD model used in the present invention by the file of 3DS type, and MOD model divides quinquepartite to form, the
A part is model identification information, face element number and number of vertex；Second part is face element index value, component index value, material index
The index value of value, color index value and vertex；Part III is the coordinate value of vertex index and point, a vertex index corresponding three
The coordinate of a point；Part IV is component index value and unit type title；Part V is material index value and Material Name.
MOD model used in the present invention is simplified model content for 3DS, and 3DS file is deposited with binary system
Storage, the inside contains the texture of model, textures etc. and calculates the present invention useless information, so during calculating, benefit
Calculate with MOD model and is more easier programming realization.Fig. 7 is a computation model used in the present invention, this computation model
Be be 10m with a side length plate and side length be 2.5m a square composition；
Step 2：Input model information carries out outside from processing is blocked to model first with method of geometry, that is, judges mesh
Face element is marked whether back to incident light direction, if the reverse vector in incident ray direction isTarget face element normal isThen by several
What relationship it is found that ifThen prove that face element back to incident ray, both belongs to the face element blocked by itself；IfIt then proves that face element is not blocked by itself, then the occlusion issue between face element is carried out using Z-BUFFER algorithm
Processing.The basic principle of Z-BUFFER efficient rendering algorithm is：By establishing Descartes three using incident direction or scattering direction as Z axis
Coordinate system is tieed up, the Y-axis of new coordinate system is projection of the coordinate system Z axis in naval vessel in new coordinate system XOY plane, target MOD model
It projects in this coordinate system, the target MOD model after projection is divided into several pictures in the XOY plane of this coordinate system
Element, the number of pixel should be much larger than target MOD model face element number, according to pixel in new coordinate system location information, save institute
There is the Pixel Information that do not blocked by other pixels in pixel, it is all to obtain target MOD model finally by the Pixel Information of preservation
The face element size that each face element is not blocked in face element thinks this face if the area that face element is blocked is less than half
Member is not blocked, else if the face element area that face element is blocked, which is more than or equal to half, then thinks that face element is blocked；Finally in mesh
All face elements that blocks are removed in mark MOD model, the target MOD model not being blocked.To treated target MOD model
Carry out rescattering calculating.
Step 3：The first judgement of rescattering between target face element pair：To all faces of target MOD model not being blocked
Member is traversed, and is successively judged as between initial face element, that is, face element 1 and remaining face element, rescattering may be occurred by finding out
Face element pair, face element is to including face element 1 and face element 2.As shown in Figure 2：n1And n2Respectively the exterior normal of face element 1 and face element 2 is sweared
Amount,For 1 center o of face element1To 2 center o of face element2Vector, by geometrical relationship it is found that if three meetAndThen think that rescattering may occur for two face elements, then execute rapid four, carries out coordinate system transformation；Otherwise it is assumed that this
Step 3 is then repeated there is no rescattering between a face element pair, rescattering between next face element pair is carried out and sentences for the first time
It is disconnected.
Step 4：Coordinate system conversion：For using the sun as incident light, it is assumed that solar incident ray is1 normal of face element
ForThen incident rayIt can be in the hope of incident ray using following geometric formulaMirror reflection wave direction on face element 1
With reflection directionAs new coordinate system, that is, S coordinate system z1Axis, x1o1y1Plane is vertical with reflection direction, S coordinate
Y in system1Axis is taken as the z-axis of naval vessel coordinate system in x1o1z1Projection in plane, naval vessel coordinate system and the conversion of S coordinate system are as follows：
Wherein θ is incidence angle of the sunlight incident direction in naval vessel coordinate system,It is sat for sunlight incident direction on naval vessel
Mark the azimuth fastened, o1x1y1z1Indicate that S coordinate system, oxyz are naval vessel coordinate system,For x in S coordinate system1Axis direction,For S
The y of coordinate system1Axis direction,For the z of S coordinate system1Axis direction.
When calculating scattering area of the face element to upper face element 1 and face element 2, since model is a three-dimensional stereo model, institute
With face element to also in two different positions in space, if directly seeking the scattering surface of face element centering face element 1 and face element 2
Difficulty is bigger when product.So establishing S coordinate system using 1 mirror image of face element scattering direction as Z axis, face element is sat to this S is projected to
The upright of face element enantiomorph can be then kept in mark system, two projections three in Calculation Plane are only needed in S coordinate system XOY plane
Angular intersecting area size can acquire the scattering area of face element centering face element 1 and face element 2 further according to coordinate system inverse transformation,
So calculating process can be simplified by establishing S coordinate system, it is readily appreciated that.
Step 5：Face element centering face element 1 and 2 scattering area of face element calculate：
Projection face element of 5.1 face elements 1 in S coordinate system is face element 11, projection face element of the face element 2 in S coordinate system is face
Member 21, under S coordinate system, face element 11With face element 21Positional relationship between the two face elements in XOY plane there are three types of：Intersection,
Include and separates；
5.2 with face element 11Three sides are successively to face element 21Three sides carry out intersection testing：If there is crosspoint, then phase is saved
The coordinate of intersection point.As shown in figure 3, utilizing face element 11Three sides successively to face element 21Three sides carry out intersection testing after, scheming
In can significantly see there are four intersection point, so four coordinates are saved；The feelings to partially overlap if there is two lines section
Condition then regards two intersection points of intersection by comprising a storage；Without intersection point if two line segments are separated from each other；
5.3 judge face element 11With face element 21It whether there is in XOY plane and mutually include：All include and portion comprising being divided into
Subpackage contains, if the part vertex of a face element of target also belongs to the case where including in another face element, is wrapped all
The apex coordinate contained saves.As shown in two triangle position relationships of Fig. 4, face element 21By face element 11All include, so conforming to
That asks shares 3 comprising point one, these three are included a preservation；
The point coordinate of 5.4 pairs of preservations judges, deletes and repeats point, if the number for deleting left point after repetition point is less than
3, then rescattering cannot occur for two Triangular object models, three be returned to step, at the beginning of the rescattering for carrying out next face element pair
Secondary judgement.Otherwise, that is, the number for deleting left point after repeating point is more than or equal to 3 and thinks that rescattering occurs, and executes step
5.5, the point of preservation is ranked up；
The point of 5.5 pairs of preservations is ranked up：To finding out under new coordinate system the smallest point of Y value in XOY plane in the point of preservation
It is set as MinP, the subtended angle size relative to MinP point successively is found out to remaining each point, and arrange each point according to subtended angle size
Sequence, such as Fig. 5, point 1, point 2, point 3, point 4 are respectively remaining four points, can be clearly seen that a little 1, point 2,3 and of point in figure
Point 4 is sequentially increased relative to the subtended angle of MinP point, so being sequentially stored into a little 1, point 2, point 3,4 this four points of point, is finally stored in
MinP point, at this point, each point saved surrounds a polygon in sequence.
The each point of all preservations is surrounded a polygon by 5.6, can regard the area of polygon as several triangles
The sum of area is calculated, it is assumed that saves a point of n (n >=3), being followed successively by number by the sequence of the point of preservation is 1~n, then may be used
This n each point is divided into the n-2 triangles such as (1,2,3), (1,3,4) ... (1, n-1, n), each bracket indicates a triangle
Finally intersecting area size can be obtained with being added to this n-2 triangle area in shape, finally utilizes new coordinate system Z axis and face
Corner dimension between two face elements of member pair, acquires face element to the scattering area size of two face elements.
Step 6：Calculate and complete the rescattering of complex target：
6.1 scatter direction and sun incident direction according to the mirror image on the face element 1 acquired in step 4, find out sunlight and enter
Incidence angle and azimuth of the direction on face element 1 are penetrated, 1 mirror image of face element scatters angle of scattering and azimuth of the direction on face element 1, root
The scattering of the mirror image on face element 1 brightness L is acquired according to the BRDF on face element 1i：
Li=f1Esun(λ)cosθi
F in formula1For the BRDF size of face element 1, Esun(λ) is the corresponding solar irradiance of fixed wave length, θiFor sunlight
The angle of incident ray and 1 normal of face element；
6.2 find out the scattering surface in face element to upper face element 1 and face element 2 according to the intersecting area size acquired in S coordinate system
Product size：As shown in fig. 6, the scattering area on face element 1 is S1, scattering area S on face element 22；
Conversion between 6.3 spoke brightness and irradiation level：As shown in fig. 6, the scattering area on face element 1 is S1, dissipate on face element 2
Penetrating area is S2, then by 1 scattering area S of face element1The spectral irradiance intensity generated on oo' is Iθr：
Iθr=Li·S1·cosθr=f1·Esun(λ)·cosθi·cosθr
Wherein θrFor the angle of face element 1 normal and two face element lines of centres；
So by S1It issues and falls on S2On radiation flux be Φ：
Φ=LicosθrS1Ω
Ω is 2 scattering area S of face element in formula2To 1 scattering area S of face element1The solid angle opened, i.e.,Face
Member 1 and the distance at 2 center of face element are R, the distance between two face element centers as shown in Figure 6, θdFor 2 normal of face element and two faces
The angle of first line of centres, then 1 scattering area S of face element1In 2 scattering area S of face element2The spectral irradiance E (λ) of upper generation is：
E (λ)=f1Esun(λ)cosθi·cosθrcosθdS1/R2
6.4 utilize BRDF, that is, f on face element 22Face element 1 can be acquired to the rescattering brightness dL of face element 2r：
dLr=f2E (λ)=f2(f1Esun(λ)cosθi)S2cosθscosθrcosθd/R2
Finally complex target is obtained to the rescattering brightness L of the sun using formula as abover,
Complete complex target rescattering calculating, as Figure 10 be the present invention using the above process calculating acquire too
The scattering brightness of target under solar irradiation background condition.It calculates model used as shown in fig. 7, being 2.5 meters by a side length
Square and side length be 10 meters square plate form, square is located at plate center, upper and lower two bottoms of square
Face while with square plate while be parallel to each other.BRDF model used is calculated as shown in figure 8, being for incidence angle as shown in the figure
45 degree, azimuth is when being 0 degree, numerical values recited of the BRDF when angle of scattering is from -90 degree to 90 degree can be significantly from figure
It arrives, when angle of scattering is 45 degree, apparent peak value occurs, the reason is that because the BRDF five-parameter model that the present invention uses is aluminium bee
Snap type has very strong mirror image to act on, so can have peak value appearance at 45 degree.Calculate solar spectrum irradiancy such as Fig. 9 used
Shown, abscissa is the wave-length coverage of visible light in figure, and ordinate is the spectral irradiance size under corresponding visible wavelength,
0.4~0.75 is the wave-length coverage of visible spectrum.Figure 10 is to utilize present invention rescattering luminance graph calculated, dotted line in figure
The scattering brightness calculation for only calculating primary scattering is indicated as a result, solid line expression calculates primary scattering and rescattering double scattering
The scattering brightness of results added.As can clearly see from the figure at 45 degree of angle of scattering, the result for calculating rescattering has
Apparent peak value.The reason is that because the BRDF model mirror image dispersion effect of the invention used is obvious, it is secondary calculating
When scattering, detector rescattering brightness can have maximum value when being in same direction with the sun.
It is one for the rescattering calculating between target face element pair when calculating scattering of the complex target to background radiation
Difficult point, the present invention are suitable for that target can occur the judgement of rescattering face element pair, and rescattering can occur for calculating
Face element to the size of scattering area, and be finally completed the calculating of rescattering of the complex target to background light radiation.
Complex target of the invention is to the rescattering calculation method of background light radiation, first input model information, to mould
Type carries out blocking processing.Face element is judged to that whether rescattering may occur using the geometrical relationship between face element, and face element is to foundation
The sequence notation of face element is face element 1 and face element 2 in reading model；The mirror image then with sunlight on face element 1 if possible occurs
Scattering direction is that Z axis establishes new coordinate system, and obtains the scattering brightness of the mirror image on face element 1 using the BRDF of face element 1, by face element pair
It projects in the XOY plane of new coordinate system, judges to project face element to the positional relationship in new coordinate system in XOY plane, to phase
Intersection point is saved comprising point, and removes repetition point；If the point number saved is less than 3, then it is assumed that this face element is to can not
Rescattering occurs, is not also just the face element pair that we find；If saving point number is greater than 3, found out in these points
Then the smallest point of Y value in new coordinate system successively calculates subtended angle size of remaining each point relative to this point, finally presses and open
Angle size successively saves point；The area of intersection is calculated using the point of preservation, polygon can be regarded as several by when calculating
It the area of triangle and is calculated, acquires face element respectively to the scattering area size of upper two face elements；By the mirror image on face element 1
Scattering brightness is converted to irradiation level using the transformational relation between irradiation level and spoke brightness, and the BRDF of face element 2 is recycled to acquire face
Rescattering brightness of first centering face element 1 to face element 2；The face elements that rescattering can occur finally all to object module into
Row as above calculates can rescattering brightness in the hope of complex target to background light radiation.
In brief, a kind of complex target provided by the invention solves the rescattering calculation method of background light radiation
Scattering area calculates and the rescattering of complex target between the judgement of rescattering, face element pair between complex target face element pair
The problem of calculating.It is embodied as：Establish object module；It inputs the MOD model information for the target established and carries out blocking processing；It is right
Rescattering is carried out between the target face element pair that blocks that treated to judge for the first time；Conversion coordinate system simultaneously calculates dissipating between face element pair
Penetrate area；The rescattering for calculating and completing complex target to background light radiation.
The present invention is and then complete by finding out calculating of the face element that rescattering occurs in object module to rescattering is carried out
At the calculating of the rescattering of entire target.Firstly the need of the face element pair that rescattering may occur is found out, then for convenience
The scattering area between face element pair is calculated, conversion coordinate system is by the face element in space to the XOY plane for projecting to conversion coordinate system
It is interior, two-dimensional problems are converted by three-dimensional problem and simplify calculating process, reduce the complexity of program, it is obtained by calculation to dissipate
Penetrating area can be in the hope of the rescattering brightness between face element pair using BRDF, and then the rescattering for obtaining entire target is bright
Degree.
Claims (4)
1. a kind of complex target is to the rescattering calculation method of background light radiation, which is characterized in that include following steps：
Step 1：Establish object module：The 3dmax model of target is established by 3dmax, then by the 3dmax target mould of foundation
Type is converted to MOD model；MOD model divides quinquepartite to form, and first part is model format identification information, face element number and vertex
Number；Second part be face element index value, component index value, material index value, color index value and vertex index value；Third portion
It is divided into the coordinate value of vertex index and point；Part IV is component index value and unit type title；Part V is material rope
Draw value and Material Name.
Step 2：Input the MOD model information of target：Model is carried out from processing is blocked first with method of geometry, then needle
To all face elements in the target MOD model that blocks that treated certainly, blocking between face element is utilized into Z-BUFFER efficient rendering algorithm
Processing, Z-BUFFER efficient rendering algorithm is by being that Z axis establishes Descartes's three-dimensional system of coordinate by incident direction or scattering direction, target
MOD model projection is divided into several pixels into this coordinate system, the target MOD model after projection in XOY plane, as
The number of element should be much larger than the face element number of model, according to the location information of pixel in a coordinate system, save in all pixels not
The Pixel Information blocked by other pixels can obtain all face elements of target MOD model finally by the Pixel Information of preservation
In the face element size that is not blocked of each face element, think this face element not if the area that face element is blocked is less than half
It is blocked, otherwise it is assumed that face element is blocked；All face elements that blocks finally are removed in target MOD model, are not blocked
Target MOD model；
Rescattering calculating is carried out to the target MOD model face element not being blocked；
Step 3：Rescattering judges for the first time between target face element pair：All face elements of the target MOD model not being blocked are traversed
Successively judged as between initial face element, that is, face element 1 and remaining face element, rescattering if possible occurs, then the two faces
Member one face element pair of composition, executes step 4, carries out coordinate system conversion, and calculate the rescattering between this face element pair, face
Member is to including face element 1 and face element 2；Step 3 is repeated if rescattering does not occur, and carries out the two of next face element pair
The secondary first judgement of scattering；
Step 4：Coordinate system conversion：For using the sun as incident light, rescattering of the target to the sun is calculated, by too
The mirror image scattering direction that solar irradiation is mapped on face element 1 is calculated in positive incident direction, establishes using mirror image scattering direction as Z axis new
The new coordinate system is defined as S coordinate system by coordinate system, and S coordinate system remains as Descartes's three-dimensional system of coordinate, face element to projecting to
In the XOY plane of S coordinate system；
Step 5：Calculate the scattering area between face element pair：In the S coordinate system that step 4 is established, the perspective plane in X0Y plane
Positional relationship between member has intersection, separation and comprising saving all intersection points and the point for including mutually between face element line segment, so
Removal repeats point afterwards, if the number of remaining point less than 3, proves that closed area cannot be formed, i.e., secondary dissipate cannot occur
It penetrates；Otherwise the smallest point of Y value is found out to remaining each point and is set as MinP, the subtended angle for successively calculating other each points relative to MinP is big
It is small, each point is ranked up according to subtended angle size, area of a polygon calculating finally is carried out to sorted point；
Step 6：Calculate and complete the rescattering of complex target：It is found out on face element 1 according to bidirectional reflectance distribution function (BRDF)
Mirror image scattering brightness size the irradiation level that face element 2 receives obtained by the transformational relation between spoke brightness and irradiation level,
Then the intersecting area size found out according to step 5 finds out face element to the scattering area size of upper face element 1 and face element 2, last root
According to the bidirectional reflectance distribution function (BRDF) on face element 2, the rescattering between face element is calculated, and then completes complicated mesh
Target rescattering calculates.
2. the rescattering calculation method of complex target according to claim 1, which is characterized in that described in step 4
Coordinate system conversion includes following steps：
4.1 set sun incident direction asThen incident rayIncident ray direction can be acquired using following geometric formulaIn face
Mirror reflection wave direction in member 1
4.2 with reflection directionAs z1Axis, x1o1y1Plane is vertical with reflection direction, y1The z-axis that axis is taken as naval vessel coordinate system exists
x1o1z1Projection in plane, naval vessel coordinate system and the conversion of S coordinate system are as follows：
Wherein o1x1y1z1Indicate that S coordinate system, oxyz are naval vessel coordinate system.
3. the rescattering calculation method of complex target according to claim 1, which is characterized in that described in step 5
The scattering area between face element pair is being calculated under S coordinate system, including is being had the following steps：
The projection face element of 5.1 face elements 1 and face element 2 in S coordinate system is to respectively face element 11With face element 21, under S coordinate system, this
Relationship between two face elements in XOY plane there are three types of：Intersect, include and separates；
5.2 by face element 11With face element 21Three sides under S coordinate system in XOY plane successively carry out intersection testing, if there is intersection
Point then saves the coordinate of crosspoint；
5.3 judge face element 11With face element 21It is complete comprising being divided into the presence or absence of mutual the case where including in XOY plane under S coordinate system
Portion includes and part includes, if the part vertex of a face element of target also belongs to the case where including in another face element,
It is all by comprising apex coordinate save；
The point coordinate of 5.4 pairs of preservations judges, deletes and repeats point, if the number of left point is less than 3 after deletion repetition point,
Rescattering cannot occur for two Triangular object models, execute step 3, otherwise, then it is assumed that rescattering occurs, executes step 5.5；
The point of 5.5 pairs of preservations is ranked up：To being found out under S coordinate system in the point of preservation, the smallest point of Y value is set as in XOY plane
MinP successively finds out the subtended angle size in XOY plane relative to MinP point to remaining each point, and according to subtended angle size to each point
It is ranked up, each point is successively then saved according to subtended angle size, each point for connecting preservation forms a polygon；
The polygon that each point of 5.6 pairs of all preservations surrounds carries out areal calculation, and the polygon surrounded is regarded as several triangles
The sum of shape area is calculated, and can be acquired and be saved the area of a polygon size that surrounds of each point, finally using S coordinate system Z axis with
Corner dimension acquires face element to the scattering area size of two face elements between two face elements of face element pair.
4. the rescattering calculation method of complex target according to claim 1, which is characterized in that described in step 6
The rescattering for calculating and completing complex target includes following steps：
6.1 scatter direction and sun incident direction according to the mirror image on the face element 1 acquired in step 4.1, find out 1 coordinate system of face element
On solar incident angle and azimuth, mirror image scatter direction angle of scattering and azimuth, the mirror image on face element 1 is acquired according to BRDF and is dissipated
Penetrate brightness Li：
Li=f1Esun(λ)cosθi
F in formula1For the BRDF size of face element 1, Esun(λ) is the corresponding solar irradiance of fixed wave length, θiFor sunlight incidence
The angle of light and 1 normal of face element；
6.2, according to corner dimension between the intersecting area size and new and old coordinate system acquired in S coordinate system, find out in face element to upper
The scattering area size of face element 1 and face element 2；
Conversion between 6.3 spoke brightness and irradiation level：Scattering area is S on face element 11, scattering area is S on face element 22, by face element
1 scattering area S1It issues and falls on 2 scattering area S of face element2On radiation flux Φ be：
Φ=LicosθrS1Ω
Ω is 2 scattering area S of face element in formula2To 1 scattering area S of face element1The solid angle opened, i.e.,θrFor face
The angle of first 1 normal and two face element lines of centres；The distance at 2 center of face element 1 and face element is R, θdFor 2 normal of face element and two
The angle of face element line, then 1 scattering area S of face element1In 2 scattering area S of face element2The spectral irradiance E of upper generation is：
E=f1Esun(λ)cosθi·cosθrcosθdS1/R2
6.4 can acquire face element 1 to the rescattering brightness dL of face element 2 using the BRDF on face element 2r：
dLr=f2(f1Esun(λ)cosθi)S2cosθscosθrcosθddλ/R2
Finally complex target is obtained to the rescattering brightness L of the sun using formula as abover,
Complete the calculating of the rescattering of complex target.
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| CN110414059A (en) * | 2019-06-28 | 2019-11-05 | 浙江大学 | The radiant energy dfensity analogy method of planar heliostats in tower type solar thermo-power station |
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Cited By (11)
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| CN110414059A (en) * | 2019-06-28 | 2019-11-05 | 浙江大学 | The radiant energy dfensity analogy method of planar heliostats in tower type solar thermo-power station |
| CN110414059B (en) * | 2019-06-28 | 2020-12-01 | 浙江大学 | Radiation energy density simulation method of planar heliostat in tower type solar thermal power station |
| CN111008461A (en) * | 2019-11-20 | 2020-04-14 | 中国辐射防护研究院 | Human body digital model design method, system and model for radiation protection |
| CN111008461B (en) * | 2019-11-20 | 2023-11-14 | 中国辐射防护研究院 | Human body digital model design method, system and model for radiation protection |
| CN111597733A (en) * | 2020-06-03 | 2020-08-28 | 清华大学 | Method for calculating solar radiation quantity of various components in space structure |
| CN111597733B (en) * | 2020-06-03 | 2022-09-23 | 清华大学 | Method for calculating solar radiation quantity of various components in space structure |
| CN112213704A (en) * | 2020-09-16 | 2021-01-12 | 西安空间无线电技术研究所 | Target scattering cross section calculation method and device |
| CN112213704B (en) * | 2020-09-16 | 2024-04-09 | 西安空间无线电技术研究所 | Target scattering cross section calculation method and device |
| CN112907720A (en) * | 2021-02-08 | 2021-06-04 | 中国海洋大学 | Sea ice data visualization method and device for realistic rendering |
| CN116091608A (en) * | 2023-04-11 | 2023-05-09 | 深之蓝海洋科技股份有限公司 | Positioning method and positioning device for underwater target, underwater equipment and storage medium |
| CN116091608B (en) * | 2023-04-11 | 2023-06-23 | 深之蓝海洋科技股份有限公司 | Positioning method and positioning device for underwater target, underwater equipment and storage medium |
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