CN111445579A - Three-dimensional terrain model adjusting method considering vector element natural feature limitation - Google Patents

Three-dimensional terrain model adjusting method considering vector element natural feature limitation Download PDF

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CN111445579A
CN111445579A CN202010433231.7A CN202010433231A CN111445579A CN 111445579 A CN111445579 A CN 111445579A CN 202010433231 A CN202010433231 A CN 202010433231A CN 111445579 A CN111445579 A CN 111445579A
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佘江峰
刘君妍
董继伟
王标
陈博
孙昱昌
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Nanjing University
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Abstract

The invention discloses a three-dimensional terrain model adjusting method considering vector element natural feature limitation, which recalculates local terrain elevation according to the natural characteristics of vector elements, realizes smooth transition between a vector area and local neighborhood terrain after recalculation and improves visualization effect. The method comprises the following steps: defining natural characteristic limiting conditions according to the attribute information of the vector elements and defining a core buffer area and a transition buffer area for the vector elements; rasterizing the vector data into a terrain elevation texture, and realizing the processing of vector elements by adjusting the elevation texture; for the core buffer area, recalculating the vector elevation according to the natural characteristics of the vector elements; and for the transition buffer area, calculating the Laplace surface of the terrain model by using a multi-grid method, and limiting the deformation of the terrain model to the transition buffer area. The method can effectively solve the problems of distortion, elevation abnormity and the like of the surface of the vector element on the basis of keeping the close fit of the vector element and the terrain model.

Description

Three-dimensional terrain model adjusting method considering vector element natural feature limitation
Technical Field
The invention belongs to the field of cartography and computer graphics, and particularly relates to a three-dimensional terrain model adjusting method based on vector element natural feature limitation.
Background
The two-dimensional vector elements are used as important components of the virtual geographic environment, and efficient and accurate fitting rendering of the two-dimensional vector elements and the three-dimensional terrain model is important content of three-dimensional GIS visualization research. Some researches on adjustment and reconstruction of the terrain covered by the vector elements are made by the scholars, including a simple smoothing method, a fine modeling method, a terrain editing method based on control points and the like. The technical background is mainly developed from the advantages and disadvantages of the above three methods.
(1) Simple smoothing method
The simple smoothing method achieves the purpose of smoothing the surface of the terrain by performing multiple smooth iterative calculations on the terrain to be modified, L iang et al embeds elements such as roads into an oblique photogrammetry model, converts oblique photogrammetry data into digital ortho-image data And digital surface model data, And realizes the combination of the roads And an urban model on a two-dimensional scale, And the smoothing of the road surface is achieved by moving average filtering.
(2) Refined modeling method
The fine modeling method is used for establishing a fine model meeting the elevation requirement for the vector data so as to match the fluctuation change of the local terrain. Brunetton et al establishes a two-dimensional triangulation patch (2D mes) based on the sampling points as vector elements and sets corresponding elevations for the patch, and superimposes the triangulation patch on the topographic layer. The method belongs to the field of fine modeling, can obtain higher display precision, and has higher calculation cost. In addition, the method cannot ensure the close fit of the vector elements and the terrain surface, and the visualization effect can be influenced in areas with large elevation changes.
(3) Control point based method
Control point-based methods require a rough understanding of the terrain surface, and control points are placed on important terrain objects of the terrain, such as mountaintops, ridges, and the like. By imposing constraints on the control points, the impact of terrain deformation on the important object objects can be controlled. Furthermore, the displacements of other points on the terrain may be calculated from their distances to the control points. However, such methods have limited terrain control and are difficult to meet with accurate terrain editing and adjustment requirements. Jenny et al propose a local deformation method for 2.5-dimensional terrain to highlight important ground object objects in a panoramic image. And calculating the displacement of other points by using an inverse distance weighting method and a moving least square method according to the mapping relation of the positions of the control points before and after deformation. In the method, the deformation of other topographic points completely refers to the control points, and characteristic limit conditions are not added according to the natural characteristics of the terrain object, so that the elevation abnormity phenomenon of 'lake uphill' can occur after deformation. The method based on the control points is developed more perfectly, and the control points can only be arranged on part of important ground objects, and the push-pull of the control points drives the movement of other points, so that the complicated editing requirement of the terrain model cannot be met.
Disclosure of Invention
The purpose of the invention is as follows: the method aims at the problem that the interaction between a vector element and a terrain model is neglected while the two-dimensional vector rendering precision and the terrain rendering precision are improved from a single angle in many conventional two-dimensional and three-dimensional laminating rendering algorithms. The invention discloses a three-dimensional terrain model adjusting method considering vector element natural feature limitation, which comprehensively considers the natural characteristics of vector elements and sets corresponding feature limitation conditions, and solves the problems of visual distortion and deformation when the vector elements are rendered on a three-dimensional terrain model by adjusting a local terrain model.
The technical scheme is as follows: in order to achieve the purpose, the invention adopts the following technical scheme:
a three-dimensional terrain model adjusting method considering vector element natural feature limitation recalculates local terrain elevation according to natural characteristics of vector elements and realizes smooth transition of the recalculated local terrain and surrounding terrain.
The method specifically comprises the following steps:
(1) the processing object of the invention selects two types of typical vector elements in the virtual geographic environment: roads and rivers. Defining feature limiting conditions according to the attribute information of the vector elements, wherein the feature limiting conditions comprise common feature limiting conditions and individual feature limiting conditions;
(2) in order to realize effective adjustment of local terrain, a core buffer area and a transition buffer area are defined for the vector elements according to the widths of the vector elements. Recalculating the elevation of the local terrain in the core buffer area, and realizing the smooth deformation of the local terrain in the transition buffer area;
(3) and dividing the terrain data according to the DEM resolution ratio to form elevation textures. Rasterizing the vector data into a terrain elevation texture to generate a terrain elevation texture containing vector information;
(4) for the vector elements representing the river, the elevation relationship between the current node and the node immediately above the current node is judged node by node starting from the starting point. Recalculating the elevation value of the current node according to the vector element individual feature limiting conditions defined in the step (1) and ensuring that the elevation value of the current node is not greater than that of the previous node;
(5) according to the vector element commonality characteristic limiting condition defined in the step (1), the vector element surface can not generate obvious elevation fluctuation. Since the vector elements are composed of discrete points, it is necessary to interpolate the node elevation into the vector element coverage to ensure that the common feature constraint defined in step (1) is satisfied. Traversing the terrain vertexes in the index area, judging the position relation between the current point and the vector element core buffer area, if the current point is in the core buffer area, re-interpolating and calculating the elevation of the point and updating the terrain elevation texture, otherwise, not processing;
(6) traversing the terrain vertexes in the index area, judging the position relation between the current point and the vector element transition buffer area, and marking the position of the corresponding point in the elevation texture as being influenced by smooth deformation if the current point is positioned in the transition buffer area. And setting Dirichlet boundary conditions outside the boundary of the transition buffer area, updating elevation textures, and limiting smooth deformation in the range of the transition buffer area.
(7) And (4) transmitting the elevation texture adjusted in the step (6) into a CUDA (computer Unified device architecture), and calculating a Laplace surface of the terrain to realize smooth transition of the local terrain and the surrounding terrain after recalculation.
The common characteristic limiting condition and the individual characteristic limiting condition related in the step (1) are respectively as follows:
Figure BDA0002501281710000031
wherein, the sigma is a self-defined threshold value;
Figure BDA0002501281710000032
and
Figure BDA0002501281710000033
represents any two points P on a straight line in the transverse direction of the road or riveriAnd PjCorresponding terrain elevations;
Figure BDA0002501281710000034
wherein gamma represents the maximum height difference between two points, and the value is determined by the specific terrain;
Figure BDA0002501281710000035
and
Figure BDA0002501281710000036
representing that any two points Q are sequentially taken in the river flow directioniAnd QjCorresponding terrain elevations.
Vector element width W in step (2)vectorCore buffer radius RCBAnd a transition buffer radius RTBThe following formula is required:
RCB＝0.5*Wvector
0≤RTB≤RCB
the step (3) specifically comprises the following steps:
(3.1) dividing the terrain data into regular grids to generate elevation textures of the terrain, taking points in each row and each column from a starting point by taking the DEM resolution as a sampling interval, connecting sampling points in each row and each column to form a two-dimensional grid, and storing a terrain elevation value at a corresponding position in each grid;
(3.2) calculating the corresponding position of each node in the terrain elevation texture according to the node coordinates (x, y) of the vector elements (the origin is positioned at the upper left corner), and expressing the corresponding position by using row and column numbers (col, row):
Figure BDA0002501281710000041
wherein, Math.floor (num) returns the maximum integer less than or equal to num, resolution.x and resolution.y respectively represent the column resolution and the row resolution of the DEM;
and (3.3) indexing the terrain elevation texture by utilizing the row and column numbers of the vector element nodes obtained by calculation to obtain the terrain elevation of the corresponding position, and storing the basic information of the vector element into the corresponding position of the terrain elevation texture.
The elevation interpolation formula in the core buffer area in the step (5) is as follows:
let AB be the two end points of the current vector line segment, P be a point in the terrain, HP，HA，HBElevation at points P, a, B, respectively:
Figure BDA0002501281710000042
where AP 'is the projected distance of AP on the line segment AB, and BP' is the projected distance of BP on AB.
The Laplace surface calculation method in the step (7) comprises the following steps: if grid (i, j) is located in the transition buffer, Δ F (i, j) is equal; otherwise, F (i, j) ═ B (i, j); where Δ is the Laplace operator; Δ F is used to capture elevation mutations in the transition buffer; is the calculated laplacian of the original terrain; the problem of high curvature caused by abrupt elevation change can be eliminated while the original topographic relief is maintained; and B (i, j) is a Dirichlet boundary value, and is set as an original elevation value of the terrain.
Further, the terrain model adjustment also comprises the step of carrying out detail optimization on corners and intersection overlapping areas of the vector elements; the method specifically comprises the following steps:
for the corner processing of the vector elements, dividing corner areas of the vector elements, generating fan-shaped corner areas between core buffer areas, and setting the elevations of points falling at the corners as the elevations of corresponding corner nodes; a quadrilateral crossing area is generated between the core buffer areas, and the average elevation of the crossing area elevation is taken as the new elevation of the area; the sector corner area generated between the transition buffer areas is also included in the range of smooth transition so as to ensure the continuity of the connection between the transition buffer areas;
for the overlapped area generated by vector intersection, setting priority for vector lines, dividing the overlapped area and the adjustment area generated by dividing the overlapped area for vector elements, wherein the elevation of the overlapped area is determined by the vector line with higher priority, and the elevation of the adjustment area is calculated by re-interpolation according to the elevation of the overlapped area.
Has the advantages that: the invention takes the vector elements as the control curve, takes the natural characteristics contained in the vector elements as the limiting conditions, and realizes the effective adjustment of the local terrain according to the specific limiting conditions. The method can remarkably improve the problems of local visualization distortion and vector element surface distortion which may occur when the vector elements are rendered on the three-dimensional terrain. In the smooth deformation part of the terrain, the CUDA is used for accelerating the calculation of the Laplace surface of the terrain, and compared with a method realized by a shader, the method can avoid complex texture switching and data organization.
Drawings
Fig. 1 is a general technical route diagram of the study of the embodiment of the present invention.
FIG. 2 is a diagram of natural feature constraint definition of vector elements in an embodiment of the present invention: (a) a common characteristic limit; (b) personality characteristic limitations.
FIG. 3 is a diagram illustrating the relationship between the vector element width and the radius of the core buffer and the transition buffer according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating buffer partitioning of vector elements according to an embodiment of the present invention.
Fig. 5 is a schematic diagram illustrating region division of a corner portion of a vector element according to an embodiment of the present invention.
FIG. 6 is a schematic diagram of region division at the intersection of vector elements according to an embodiment of the present invention.
FIG. 7 is a diagram of the effect of the method of the embodiment of the invention after adjustment: (a) adjusting the previous road; (b) the adjusted road; (c) adjusting the river before; (d) and adjusting the river.
Detailed Description
The technical solution of the present invention is further described with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, a three-dimensional terrain model adjusting method considering vector element natural feature constraints disclosed in the embodiment of the present invention mainly includes four steps of vector element rasterization, terrain elevation recalculation, smooth deformation of local terrain, and detail optimization. Firstly, rasterizing vector elements into the elevation texture of the terrain to generate the elevation texture containing vector information; secondly, recalculating local terrain elevation according to the feature limit of the vector elements; then, aiming at the elevation abrupt change generated after recalculation, a transition buffer area is arranged, and smooth transition of the terrain is realized through deformation; finally, the detail optimization includes corner region processing and overlap region processing. The following describes the definition of the natural feature restriction and the division of the buffer area of the vector elements, the rasterization of the vector elements, the calculation of the terrain elevation and the smooth deformation, and the detail optimization in the embodiment of the present invention.
(1) Feature constraint definition
Vector elements included in the virtual geographic environment are various in types, and a universal characteristic limiting condition cannot be uniformly defined for all vector elements. Therefore, two representative types of vector element roads and rivers in the virtual geographic environment are selected to illustrate the feature limitation. Roads and rivers, being well-defined geographic entities, have natural feature limitations that they must follow to constrain local terrain morphology. The characteristic limit conditions are divided into two types of commonalities and personalities, wherein the commonalities characteristic limit refers to the limit conditions commonly followed by roads and rivers, and the personalities characteristic limit refers to the limit conditions unique to the rivers.
For the common limitation, it is required that the road and river surfaces remain flat, i.e. there cannot be significant undulations in the cross-section of the vector elements. Taking a road as an example (see (a) in fig. 2), an auxiliary straight line x is drawn in the transverse direction of the road symbol, and arbitrary two points P are taken on the linei(m,yi) And Pj(m,yj) Two points correspond to a terrain elevation of
Figure BDA0002501281710000061
And
Figure BDA0002501281710000062
then there are:
Figure BDA0002501281710000063
wherein, σ is a self-defined threshold value, and the value thereof is generally 0 or a positive number slightly larger than 0.
For individual restrictions, the river is a special vector element, and has a special constraint property that the river elevation cannot be increased along the extending direction of the river. Two arbitrary points are sequentially taken in the river flow direction (see (b) in fig. 2), and the coordinates are Qi(xi,yi) And Qj(xj,yj) Two points correspond to a terrain elevation of
Figure BDA0002501281710000064
And
Figure BDA0002501281710000065
then there are:
Figure BDA0002501281710000066
wherein gamma represents the maximum height difference between two points, and the value is determined by the specific terrain.
(2) Buffer partitioning
In order to realize effective adjustment of local terrain, the neighborhood of vector elements needs to be divided, and different divided areas are processed differently. Specifically, the neighborhood of the vector element is divided into a Core Buffer (CB) and a Transition Buffer (TB) according to the influence range of the vector element. Wherein local terrain elevations are recalculated in the core buffer based on natural characteristics of the vector elements, such that the radii thereof generally depend on the widths of the vector elements; in order to achieve smooth transition between the adjusted terrain and the terrain surrounding the adjusted terrain in the transition buffer zone, the relationship between the radius of the transition buffer zone and the smooth deformation effect of the terrain needs to be balanced in order to maintain the details of the terrain to the maximum extent. As shown in FIG. 3, the vector element width WvectorCore buffer radius RCBAnd a transition buffer radius RTBSatisfies the formula:
Figure BDA0002501281710000067
the radius of the core buffer area is half of the width of the vector element, the core buffer area is constructed by constructing quadrangles on two sides of each vector line segment according to the width of the vector element to form the core buffer area, and the length of the core buffer area is L the length of the current vector elementlineAnd the width is the width of the vector element. The transition buffer area is a quadrilateral area (not including core buffer area) distributed at two sides of the core buffer area, and is constructed in a similar way to the core buffer area, and the radius of the transition buffer area is proper (not including the core buffer area)Greater than RCB) The length is consistent with the length of the current line segment.
(3) Vector element rasterization
Vector elements and terrain data are two independent data layers, and if two layers of data are processed separately, the joint degree of the two layers of data can be influenced, so that the vector elements are rasterized into corresponding grids of a terrain elevation texture, and the processing of the vector elements is converted into the processing of the terrain data. The method comprises the following specific steps: and dividing the terrain area attached with the vector elements into regular grids to form terrain elevation textures, wherein the size of the grids is equal to the DEM resolution (resolution. x, resolution. y) of the terrain. From the coordinates (x, y) of the points constituting the vector elements (the upper left corner is the origin), the position of each coordinate point in the terrain elevation texture is calculated and represented by the row and column number (row, col):
Figure BDA0002501281710000071
where Math. floor (num) returns the largest integer less than or equal to num, resolution. x and resolution. y represent the column resolution and row resolution of the DEM, respectively.
The terrain elevation at the corresponding position can be obtained by indexing the terrain elevation texture through row and column numbers (row, col), and the terrain elevation texture after rasterization processing contains basic information of vector elements and is used for local elevation recalculation. The basic information of the vector element includes a vector line ID, a vector line type, a vector line color, a vector line priority, and the like.
(4) Terrain elevation recalculation
And recalculating the elevation value corresponding to the vector element in the terrain elevation texture according to the characteristic limit condition. Vector elements have no width, and generally consist of a series of discrete coordinate points, and a plurality of grids are often spanned between two adjacent coordinate points, so that the elevation values of two adjacent points need to be interpolated into an internal buffer area, and the interpolation method adopts linear interpolation. For the vector elements representing the river, the elevation relationship between the current node and the node immediately above the current node is judged node by node starting from the starting point. And recalculating the elevation value of the current node according to the defined individual characteristic limiting conditions of the vector elements, and ensuring that the elevation value of the current node is not greater than the elevation value of the previous node. According to the defined vector element commonality characteristic limiting condition, the vector element surface can not generate obvious elevation fluctuation, and the node elevation needs to be interpolated into the vector element coverage range to ensure that the defined commonality characteristic limiting condition is met.
The range of elevation recalculation is an area composed of the core buffer area of each line segment constituting the vector element. Before calculation, it is necessary to determine which grid points in the high texture are within the core buffer. As shown in fig. 4, let P be a point in the terrain, and if the current point P is in the internal buffer area, perform an elevation interpolation on the point P according to the projection distances AP 'and BP' from the point P to the two end points AB of the line segment; otherwise, no modification is made.
Figure BDA0002501281710000072
Wherein AP 'is the projection distance of AP on the line segment AB, BP' is the projection distance of BP on AB, HP，HA，HBElevation at points P, a, B, respectively.
The influence range of the vector elements is generally only a part of the terrain, and if all points on the terrain are traversed, some points which are obviously not in the influence range of the vector elements can be unnecessarily judged, and the efficiency of the algorithm is influenced. To avoid indexing the entire terrain, a rectangular block containing its core buffer and transition buffer, called the index region, is defined for each vector line segment. The number of comparisons can be reduced and the performance of the algorithm improved within the defined range rather than the position of the decision point of the whole study area.
(5) Smooth deformation of local topography
In order to solve the problem of abrupt elevation change generated after local elevation recalculation, transition buffer areas are established on two sides of a core buffer area, and deformation adjustment is carried out on a local terrain by calculating a Laplace surface of the terrain.
The laplacian is a differential operator, widely applied to the field of digital image processing, and is commonly used for capturing gray level abrupt changes in images. Likewise, the laplacian operator can also be used to extract elevation mutations in elevation texture. In order to eliminate the abrupt elevation change caused by the elevation recalculation, an energy minimization formula (6)) of the terrain surface can be derived according to the detail information of the terrain and the laplacian operator, and the smooth deformation of the terrain surface is converted into the solution of the laplacian equation (the energy minimization surface calculated according to the laplacian equation is called the laplacian surface). And setting Dirichlet boundary conditions at the boundary of the smooth transition, thereby realizing that the smooth deformation is limited in the range of the transition buffer zone and reducing the modification amount of the terrain as much as possible.
Figure BDA0002501281710000081
Where Δ is the Laplace operator; Δ F is used to capture elevation mutations in the transition buffer; is the calculated laplacian of the original terrain; the problem of high curvature caused by abrupt elevation change can be eliminated while the original topographic relief is maintained; b (i, j) is a Dirichlet boundary value, which is set as the original elevation value of the terrain.
(6) Detail optimization
And (3) vector element corner processing:
for the core buffer area, since there may be a change in angle between two adjacent line segments, a sector-shaped corner area is generated, and the terrain elevation of the area also needs to be processed accordingly to ensure continuity of terrain elevation adjustment. Referring to FIG. 5, two connected segments AB, BC and their core buffers A1A2B2B1And B'1B′2C2C1For example, B1BB′1Is a corner region, BB'2IB2Is the overlap region. Let P be a point in the coverage of segments AB and BC, and the distance from P to AB be PH1The distance from P to BC is PH2The angle between PB and BC is α, then P is in B1BB′1The internal judgment conditions are as follows:
Figure BDA0002501281710000091
p is BB'2IB2The judgment conditions in the region are as follows:
Figure BDA0002501281710000092
for B1BB′1Inner points, whose elevation is simply set to the elevation of B; for BB'2IB2And taking the average elevation value of the overlapped area as the new elevation of the overlapped area.
For the transition buffers, due to the corner regions B between the core buffers1BB′1Has been correspondingly modified, then B1BB′1Abrupt elevation changes also occur with its surrounding terrain. Thus corner region B1BB′1Smooth transitions with its surrounding terrain also need to be taken into account. In addition, to ensure the transition region A3A1B1B3And B'3B′1C1C3Continuity between, connecting regions B3B1B′1B′3Needs to be included in the range of smooth deformation. Specifically, the processing method of the transition buffer corner is similar to that of the core buffer: first, the position of P point is determined, if P point is located at B3B1B′1B′3Within the region, the point will be affected by the smooth transition; second, by setting Dirichlet boundary conditions, smooth transitions can be limited to boundaries
Figure BDA0002501281710000093
And
Figure BDA0002501281710000094
in the meantime. Judging point P is at B3B1B′1B′3The internal conditions are:
Figure BDA0002501281710000095
vector element overlapping processing:
the intersection of the vector elements generates an Overlapping area (Overlapping area), and the elevation of the Overlapping area is affected by a plurality of vector lines when the elevation adjustment is performed. To solve the problem of elevation conflicts that may arise when computing the elevations of overlapping areas, we prioritize vector lines whose elevations are determined by higher priority vector lines (and collectively if the vector lines are of the same priority). As shown in fig. 6, the line segment AB intersects the line segment CD at the point O, creating an overlap area GFHE, the line segment CD is divided by the overlap area GFHE and two new areas C are created1GEC2And FD1D2H, called adjustment area (adjustment area). Line segment AB has a higher priority than line segment CD in FIG. 6, so that the core buffer A of AB is preferentially recalculated according to the natural characteristics of AB1A2B2B1The elevation of the inside and the elevation of the overlap area GFHE is also determined by the higher priority segment AB. Furthermore, to ensure a natural transition in elevation between the overlap region GFHE and the two adjustment regions, C1GEC2The elevation of the coverage is obtained according to the elevation interpolation of C and C', FD1D2And the elevation of the H coverage range is obtained according to the elevation interpolation of the D and the D'.
Fig. 7 shows an effect diagram of a terrain model adjusted by using the invention. Fig. 7 (a) shows an intersection consisting of two intersecting roads; fig. 7 (c) shows a composite river composed of a combination of a branch flow and a main flow. Fig. 7 (b) and (d) show the effect of the terrain model adjusted by the method proposed in the present study, the water surface and the road surface are flat, and the intersection of the vector line and other portions can be naturally transited. The terrain model adjusted by the method has no obvious elevation fluctuation on the road surface, and the problem of abnormal elevation rise along the river flow direction is solved. In addition, the vector elements can still keep close fit with the terrain model, and the overall relief feeling of the terrain is also kept.

Claims (7)

1. A three-dimensional terrain model adjusting method considering vector element natural feature limitation is characterized by comprising the following steps:
(1) defining natural feature limiting conditions including common feature limiting conditions and individual feature limiting conditions according to the attribute information of the vector elements;
(2) defining a core buffer area and a transition buffer area for the vector elements according to the width of the vector elements;
(3) dividing topographic data according to DEM resolution to form elevation texture; rasterizing the vector data into the elevation texture of the terrain model to generate a terrain elevation texture containing vector information;
(4) for vector elements representing the river, judging the elevation relation between the current node and the previous node by node from the starting point, recalculating the elevation value of the current node according to the individual characteristic limiting conditions defined in the step (1), and ensuring that the elevation value of the current node is not greater than the elevation value of the previous node;
(5) interpolating the elevation of the nodes into the coverage range of the vector elements to ensure that the common characteristic limiting conditions defined in the step (1) are met; traversing the terrain vertexes in the index area, judging the position relation between the current point and the vector element core buffer area, if the current point is in the core buffer area, re-interpolating and calculating the elevation of the point and updating the terrain elevation texture, otherwise, not processing;
(6) traversing the topographic vertices in the index area, judging the position relationship between the current point and the vector element transition buffer area, and marking the position of the corresponding point in the elevation texture as being influenced by smooth deformation if the current point is positioned in the transition buffer area; setting Dirichlet boundary conditions outside the boundary of the transition buffer area, updating elevation textures, and limiting smooth deformation in the range of the transition buffer area;
(7) and (4) transmitting the elevation texture adjusted in the step (6) into a CUDA (compute unified device architecture), and calculating the Laplacian surface of the terrain to realize smooth transition of the local terrain and the surrounding terrain after recalculation.
2. The method for adjusting the three-dimensional terrain model considering the constraint of the natural features of the vector elements as claimed in claim 1, wherein the generic feature constraint conditions and the individual feature constraint conditions involved in the step (1) are respectively as follows:
Figure FDA0002501281700000011
wherein, the sigma is a self-defined threshold value;
Figure FDA0002501281700000012
and
Figure FDA0002501281700000013
represents any two points P on a straight line in the transverse direction of the road or riveriAnd PjCorresponding terrain elevations;
Figure FDA0002501281700000014
wherein gamma represents the maximum height difference between two points, and the value is determined by the specific terrain;
Figure FDA0002501281700000015
and
Figure FDA0002501281700000016
representing that any two points Q are sequentially taken in the river flow directioniAnd QjCorresponding terrain elevations.
3. The method for adjusting a three-dimensional terrain model considering the constraint of natural features of vector elements as claimed in claim 1, wherein the vector element width W in step (2)vectorCore buffer radius RCBAnd a transition buffer radius RTBThe following formula is satisfied:
RCB＝0.5*Wvector
0≤RTB≤RCB。
4. the method for adjusting a three-dimensional terrain model considering the constraint of natural features of vector elements according to claim 1, wherein the step (3) specifically comprises:
(3.1) dividing the terrain data into regular grids to generate elevation textures of the terrain, taking points in each row and each column from a starting point by taking the DEM resolution as a sampling interval, connecting sampling points in each row and each column to form a two-dimensional grid, and storing a terrain elevation value at a corresponding position in each grid;
(3.2) calculating the corresponding position of each node in the terrain elevation texture according to the node coordinates (x, y) of the vector elements, and expressing the corresponding position by using row and column numbers (col, row):
Figure FDA0002501281700000021
wherein, Math.floor (num) returns the maximum integer less than or equal to num, resolution.x and resolution.y respectively represent the column resolution and the row resolution of the DEM;
and (3.3) indexing the terrain elevation texture by utilizing the row and column numbers of the vector element nodes obtained by calculation to obtain the terrain elevation of the corresponding position, and storing the basic information of the vector element into the corresponding position of the terrain elevation texture.
5. The method for adjusting a three-dimensional terrain model considering the limitation of natural features of vector elements according to claim 1, wherein the elevation interpolation formula in the core buffer area in the step (5) is as follows:
let AB be the two end points of the current vector line segment, P be a point in the terrain, HP，HA，HBElevation at points P, a, B, respectively:
Figure FDA0002501281700000022
where AP 'is the projected distance of AP on the line segment AB, and BP' is the projected distance of BP on AB.
6. The method for adjusting a three-dimensional terrain model considering the constraint of natural features of vector elements according to claim 1, wherein the laplacian surface calculation method in the step (7) is as follows: if grid (i, j) is located in the transition buffer, Δ F (i, j) is equal; otherwise, F (i, j) ═ B (i, j); where Δ is the Laplace operator; Δ F is used to capture elevation mutations in the transition buffer; is the calculated laplacian of the original terrain; and B (i, j) is a Dirichlet boundary value, and is set as an original elevation value of the terrain.
7. The method of claim 1, further comprising performing detail optimization on vector element corners and intersection overlap regions; the method specifically comprises the following steps:
for the corner processing of the vector elements, dividing corner areas of the vector elements, generating fan-shaped corner areas between core buffer areas, and setting the elevations of points falling at the corners as the elevations of corresponding corner nodes; a quadrilateral crossing area is generated between the core buffer areas, and the average elevation of the crossing area elevation is taken as the new elevation of the area; the sector corner area generated between the transition buffer areas is brought into the range of smooth transition, and the continuity of connection between the transition buffer areas is ensured;
for the overlapped area generated by vector intersection, setting priority for vector lines, dividing the overlapped area and the adjustment area generated by dividing the overlapped area for vector elements, wherein the elevation of the overlapped area is determined by the vector line with higher priority, and the elevation of the adjustment area is calculated by re-interpolation according to the elevation of the overlapped area.
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112017288A (en) * 2020-08-28 2020-12-01 滁州学院 DEM (digital elevation model) synthesis and simplification method based on topographic map data
CN112530012A (en) * 2020-12-24 2021-03-19 网易（杭州）网络有限公司 Virtual earth surface processing method and device and electronic device
CN113822997A (en) * 2021-11-23 2021-12-21 四川易利数字城市科技有限公司 Method and system for adjusting elevation by using bitmap information
CN113836751A (en) * 2021-11-22 2021-12-24 武汉峰岭科技有限公司 Automatic adjustment method and system for digital elevation model based on contour line stretching
CN114707254A (en) * 2022-06-01 2022-07-05 中国空气动力研究与发展中心计算空气动力研究所 Two-dimensional boundary layer grid generation method and system based on template construction method
CN115222908A (en) * 2022-07-20 2022-10-21 北京数字政通科技股份有限公司 Automatic construction method and system for three-dimensional road in digital twinning
CN115617815A (en) * 2022-11-21 2023-01-17 四川省公路规划勘察设计研究院有限公司 Method and system for carrying index information by using height-limited model redundant space

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102651141A (en) * 2012-03-30 2012-08-29 北京师范大学 Method for automatically superposing and rendering vector map and high-resolution digital elevation models in large scene
CN105023288A (en) * 2015-07-09 2015-11-04 南京大学 A method for eliminating visual errors of two-dimensional vector solid lines in a three-dimensional scene
CN107154070A (en) * 2016-03-04 2017-09-12 高德软件有限公司 Vector element and digital terrain model stacking method and device
US20170365094A1 (en) * 2016-04-04 2017-12-21 University Of Cincinnati Localized Contour Tree Method for Deriving Geometric and Topological Properties of Complex Surface Depressions Based on High Resolution Topographical Data
CN110276732A (en) * 2019-06-18 2019-09-24 昆明理工大学 A kind of mountain area point cloud cavity restorative procedure for taking features of terrain line feature into account

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102651141A (en) * 2012-03-30 2012-08-29 北京师范大学 Method for automatically superposing and rendering vector map and high-resolution digital elevation models in large scene
CN105023288A (en) * 2015-07-09 2015-11-04 南京大学 A method for eliminating visual errors of two-dimensional vector solid lines in a three-dimensional scene
CN107154070A (en) * 2016-03-04 2017-09-12 高德软件有限公司 Vector element and digital terrain model stacking method and device
US20170365094A1 (en) * 2016-04-04 2017-12-21 University Of Cincinnati Localized Contour Tree Method for Deriving Geometric and Topological Properties of Complex Surface Depressions Based on High Resolution Topographical Data
CN110276732A (en) * 2019-06-18 2019-09-24 昆明理工大学 A kind of mountain area point cloud cavity restorative procedure for taking features of terrain line feature into account

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
SHE J , LI X , LIU J , ET AL.: "A building label placement method for 3D visualizations based on candidate label evaluation and selection", 《INTERNATIONAL JOURNAL OF GEOGRAPHICAL INFORMATION SCIENCE》 *
刘君妍; 陈雅茜; 高亦远; 李创; 佘江峰: "一种基于屏幕的三维地图线状符号渲染方法", 《地球信息科学学报》 *
杨玲;张立强;康志忠;肖志强;彭军还;张兴明;刘骝: "大规模矢量地图与多分辨率DEM快速叠加的方法", 《中国科学:信息科学》 *
王姣姣: "矢量数据三维可视化研究进展", 《广东农业科学》 *
简灿良; 叶荣青: "基于正射影像与高程模型匹配的地表更新方法", 《系统仿真学报》 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112017288A (en) * 2020-08-28 2020-12-01 滁州学院 DEM (digital elevation model) synthesis and simplification method based on topographic map data
CN112017288B (en) * 2020-08-28 2023-10-31 滁州学院 DEM (digital elevation model) synthesis and simplification method based on topographic map data
CN112530012A (en) * 2020-12-24 2021-03-19 网易（杭州）网络有限公司 Virtual earth surface processing method and device and electronic device
CN113836751A (en) * 2021-11-22 2021-12-24 武汉峰岭科技有限公司 Automatic adjustment method and system for digital elevation model based on contour line stretching
CN113822997A (en) * 2021-11-23 2021-12-21 四川易利数字城市科技有限公司 Method and system for adjusting elevation by using bitmap information
CN114707254A (en) * 2022-06-01 2022-07-05 中国空气动力研究与发展中心计算空气动力研究所 Two-dimensional boundary layer grid generation method and system based on template construction method
CN115222908A (en) * 2022-07-20 2022-10-21 北京数字政通科技股份有限公司 Automatic construction method and system for three-dimensional road in digital twinning
CN115222908B (en) * 2022-07-20 2024-04-02 北京数字政通科技股份有限公司 Automatic construction method and system for three-dimensional road in digital twin
CN115617815A (en) * 2022-11-21 2023-01-17 四川省公路规划勘察设计研究院有限公司 Method and system for carrying index information by using height-limited model redundant space

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