A simulation method for real-time deformation of coal wall in a three-dimensional engine

Abstract

The application provides a simulation method for real-time deformation of a coal wall in a three-dimensional engine and belongs to the technical field of coal wall deformation simulation. The application solves the problems of rough effect, large computer computing power consumption and poor simulation effect of fine coal wall deformation in existing coal mine simulation demonstration or simulation. The application comprises the following steps: scene dynamic loading, including space division and occlusion culling; simulation of deformation of a coal wall caused by coal cutting by a coal mining machine, including coal mining machine drum sampling, data sampling based on a device model, sampling of data directly contacting the coal wall by the coal mining machine drum part; coal wall mesh vertex sampling, asynchronous traversal of all vertex points of the coal wall for storage at initial loading, retrieval of an interaction area on the coal wall through the sampling points of the drum after all sample points are recorded, and displacement deformation of a grid of a contact point according to the posture of the coal mining machine when a threshold is reached. The application is applied to coal wall shape simulation.

Description

Technical Field

[0001] This invention provides a simulation method for real-time deformation of coal walls in a 3D engine, belonging to the field of coal wall deformation simulation technology in mines. Background Technology

[0002] Currently, most coal mine simulations use animation. However, in digital twins, the overall mining workflow, process demonstrations, and process backtracking of coal mines often use direct drilling of holes in the mesh surface to demonstrate the deformation effects of the coal wall during coal cutting, which is relatively crude. There is no mature solution for achieving more refined coal wall deformation effects.

[0003] Currently, the simulation of coal face deformation in digital twin technology related to fully mechanized mining faces is lacking. In the 3D engine Unity3D, the biggest obstacle to recreating the shape changes of the coal face is the excessive number of models in the scene. At the same time, real-time synchronization, rendering, and real-time data of the underground status all consume a lot of computing power.

[0004] Currently, the common solution for mesh deformation in 3D engines is to control the movement of mesh vertices. The finer the mesh, the higher the fidelity of the deformation effect. However, the sheer number of high-precision meshes brings a huge computational load. In digital twin simulations of coal mines, the rendering of mechanical equipment and coal wall environment, as well as the driving of real-time data, all consume a lot of computing power. Therefore, it is necessary to focus on optimizing efficiency. Summary of the Invention

[0005] To address the problems of rough effects, high computing power consumption, and poor simulation of fine coal wall deformation in existing coal mine simulation demonstrations or simulations, this invention proposes a simulation method for real-time coal wall deformation in a 3D engine.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a simulation method for real-time deformation of coal wall in a three-dimensional engine, comprising the following steps:

[0007] S1: Dynamic scene loading: includes:

[0008] S1.1: Spatial partitioning: Using the octree algorithm, the scene is spatially partitioned based on the viewpoint when the scene is initially loaded. When the viewpoint changes, spatial retrieval is performed based on the octree to update the visibility status of devices and the environment within the scene.

[0009] S1.2: Occlusion culling: Using traditional LOD loading scene and view frustum culling;

[0010] S2: Simulation of coal wall deformation during coal cutting by a coal mining machine: including:

[0011] S2.1: Coal mining machine drum sampling, based on the equipment model, sampling the data of the coal mining machine drum that is in direct contact with the coal wall;

[0012] S2.2: Coal wall mesh vertex sampling. During the initial loading, all vertex points of the coal wall are asynchronously traversed and stored. After all sample points are entered, the interactive area on the coal wall is retrieved through the sampling points of the drum. When the threshold is reached, the mesh of the contact point is pushed and deformed according to the posture of the coal mining machine.

[0013] The mesh shifting deformation in step S2.2 includes two steps: deformation calculation at the midpoint of the mesh and deformation calculation at the outer perimeter of the mesh.

[0014] The process for calculating the deformation of the outer points of the grid is as follows:

[0015] The vertex coordinates (x, y, z) on the triangular mesh are considered as three independent scalar fields. Each triangular patch on the mesh has three independent gradient fields, which change as the control point set moves during deformation. When the user drags the control point set on the mesh, the formula for calculating the deformation of the outer points of the mesh is as follows:

[0016]

[0017] In the above formula: Φ is the coordinate of the mesh after deformation, w is the gradient field after mesh deformation, A is the area of ​​the triangle, and Ω is the domain;

[0018] According to the variational method, minimizing the above equation is equivalent to solving the Poisson equation.

[0019] The formula for calculating the deformation of the outer points of the mesh can be further expressed as solving a system of sparse linear equations:

[0020] LΦ = b;

[0021] Where L is the Laplacian operator of the grid, and b is the divergence value of the gradient field w at the grid vertex.

[0022] The process for calculating the deformation at the midpoint of the grid is as follows:

[0023] Let f be a piecewise linear function, where f is a piecewise linear function in each triangular piece {x} of the grid. i x j x k At the vertex of}, there is f(x) i )=f i f(x) j )=f j f(x) k )=f k The value of f at each point on the triangle is calculated using linear interpolation:

[0024] f(x)=f i φ i +f j φ j +f k φ k ;

[0025] The gradient of f is as follows:

[0026]

[0027] in The expression is:

[0028] Calculate in sequence The expression is given by ⊥, where ⊥ represents rotating the vector counterclockwise by 90 degrees, and A represents the area of ​​the triangle.

[0029] Let w be a vector-valued function: S→R 3 S represents the grid, R 3 Let represent the mapping function from a vertex to 3D space, and w represent the vector on each triangle. Then w at vertex x... i The divergence at a given point is defined as:

[0030]

[0031] Where T(x) i ) represents vertex x i A ring neighborhood triangle T This represents the area of ​​triangle T;

[0032] Substituting the gradient operator expression into the divergence operator expression yields the vertex x. i The Laplace operator expression at:

[0033]

[0034] Where N(x) i ) represents the contact point x i α, a ring neighborhood point ij β ij Let be the opposite angle of edge ij. Smooth the mesh vertices according to the Laplace operator expression at each vertex.

[0035] The advantages of this invention compared to the prior art are as follows: This invention optimizes the rendering method in the 3D engine by using a combination of multi-threading and octrees to perform scene-by-scene partitioning rendering of scene resources; the coal cutting deformation effect is optimized by using quadtrees to update the deformed mesh points in real time, which can produce a coal wall deformation effect with relatively high simulation; the coal wall deformation mesh sampling and storage improves the efficiency of coal wall mesh deformation update. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings:

[0037] Figure 1 This is a flowchart of the method of the present invention;

[0038] Figure 2 This is a schematic diagram illustrating the spatial region division of this invention. Detailed Implementation

[0039] like Figure 1-2 As shown, in order to solve the problem of high computational cost in simulating coal wall morphology using existing 3D engines, this invention introduces an octree algorithm to perform batch rendering of the scene according to spatial region division, thereby reducing rendering pressure. For the coal wall deformation part, by sampling the coal wall vertex, ignoring the axial value in the advancing direction, and storing the data according to the quadtree after traversal, after the pose of the coal mining equipment is updated, the mesh vertex list of the deformation part is updated based on its sampling area to perform deformation processing.

[0040] The simulation method for destructible terrain in a 3D engine provided by this invention is used to simulate the deformation of the coal face during coal cutting by a coal mining machine. The flowchart of the method is as follows: Figure 1 As shown, the main steps are as follows:

[0041] 01) For rendering mechanical equipment and the environment, efficiency optimization is divided into two directions. One is using traditional LOD loading and view frustum culling; the other is using an octree algorithm to spatially divide the scene based on the viewpoint during initial scene loading. When the viewpoint changes, spatial retrieval is performed based on the octree to update the visibility status of equipment and the environment within the scene. A schematic diagram of spatial region division is shown below. Figure 2 As shown, Figure 2 The white area represents objects displayed within the viewing area, while the black area represents hidden objects. The black area outside the triangular area represents the portion of the view frustum that has been removed. This method can highlight objects within the viewing area and blur or remove objects outside the viewing area or in the distance without consuming too much computing power.

[0042] 02) Simulation of coal wall deformation during coal cutting by a coal mining machine

[0043] a) Sampling of the coal mining machine drum: Data sampling is performed based on the equipment model, and data on the part of the coal mining machine drum that is in direct contact with the coal wall is sampled.

[0044] b) Coal wall mesh vertex sampling: During initial loading, all vertex points of the coal wall are asynchronously traversed and stored. The data entry structure of this invention adopts a quadtree. The data model of the coal mining machine can be simplified to operating and updating data in two dimensions. After all sample points are entered, the interactive area on the coal wall is retrieved through the sampling points of the drum. When a threshold is reached, that is, when the drum contacts the coal wall in the coal mining advance direction, the mesh at the contact point is pushed and deformed according to the attitude of the coal mining machine.

[0045] The calculation of mesh deformation in this invention includes two parts: deformation calculation of points on the outer perimeter of the mesh and deformation calculation of points in the middle of the mesh.

[0046] The deformation calculation for the outer points of the mesh is as follows: Considering the vertex coordinates (x, y, z) of the triangular mesh as three independent scalar fields, each triangular patch on the mesh has three independent gradient fields. These gradient fields are differential properties of the mesh, equivalent to its characteristics, and change with the movement of the control point set during deformation. Therefore, when the user drags the control point set on the mesh, the mesh deformation problem becomes solving the following equation:

[0047]

[0048] According to the variational method, minimizing the above equation is equivalent to solving the Poisson equation:

[0049]

[0050] Where Φ is the coordinate of the deformed mesh to be determined, and w is the gradient field after mesh deformation.

[0051] The above equation can be further expressed as solving a sparse linear system of equations:

[0052] LΦ = b;

[0053] Where L is the Laplacian operator of the grid, and b is the divergence value of the gradient field w at the grid vertex.

[0054] The deformation calculation at the midpoint of the mesh is as follows: Let f be a piecewise linear function, where f is the deformation at each triangular piece {x} in the mesh. i x j x k At the vertex of}, there is f(x) i )=f i f(x) j )=f j f(x) k )=f kBy using linear interpolation, we can determine the value of f at each point on the triangle:

[0055] f(x)=f i φ i +f j φ j +f k φ k ;

[0056] Thus, the gradient of f is as follows:

[0057]

[0058] It can be obtained through simple calculation. The expression is:

[0059]

[0060] Similarly, it can be written as The expression is given by ⊥, where ⊥ represents rotating the vector counterclockwise by 90 degrees, and A represents the area of ​​the triangle.

[0061] Let w be a vector-valued function: S→R3, where S represents the mesh and w represents the vector on each triangle. Then w at vertex x i The divergence at a point can be defined as:

[0062]

[0063] Where T(x) i ) represents vertex x i A ring neighborhood triangle T This represents the area of ​​triangle T.

[0064] Substituting the gradient operator expression into the divergence operator expression yields the vertex x. i The Laplace operator at the location is of the following form:

[0065]

[0066] Where N(x) i ) represents the contact point x i The 1-ring neighborhood points are used to smooth the mesh vertices, α. ij It means that β ij express

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A simulation method for real-time deformation of coal face in a 3D engine, characterized in that, Includes the following steps: S1: Dynamic scene loading: includes: S1.1: Spatial partitioning: Using the octree algorithm, the scene is spatially partitioned based on the viewpoint when the scene is initially loaded. When the viewpoint changes, spatial retrieval is performed based on the octree to update the visibility status of devices and the environment within the scene. S1.2: Occlusion culling: Using traditional LOD loading scene and view frustum culling; S2: Simulation of coal wall deformation during coal cutting by a coal mining machine: including: S2.1: Coal mining machine drum sampling, based on the equipment model, sampling the data of the coal mining machine drum that is in direct contact with the coal wall; S2.2: Coal wall mesh vertex sampling. During the initial loading, all vertex points of the coal wall are asynchronously traversed and stored. After all sample points are entered, the interactive area on the coal wall is retrieved through the sampling points of the drum. When the threshold is reached, the mesh of the contact point is pushed and deformed according to the posture of the coal mining machine.

2. The simulation method for real-time deformation of coal wall in a three-dimensional engine according to claim 1, characterized in that: The mesh shifting deformation in step S2.2 includes two steps: deformation calculation at the midpoint of the mesh and deformation calculation at the outer perimeter of the mesh.

3. The simulation method for real-time deformation of coal wall in a three-dimensional engine according to claim 2, characterized in that: The process for calculating the deformation of the outer points of the grid is as follows: The vertex coordinates (x, y, z) on the triangular mesh are considered as three independent scalar fields. Each triangular piece on the mesh has three independent gradient fields, which change as the control point set moves during deformation. When the user drags the control point set on the mesh, the formula for calculating the deformation of the outer points of the mesh is as follows: ； In the above formula: Let be the coordinates of the deformed mesh. The gradient field after mesh deformation. Let Ω be the area of ​​the triangle, and Ω be the domain. According to the variational method, minimizing the above equation is equivalent to solving the Poisson equation. .

4. The simulation method for real-time deformation of coal wall in a three-dimensional engine according to claim 3, characterized in that: The formula for calculating the deformation of the outer points of the mesh can be further expressed as solving a system of sparse linear equations: ； in For the Laplace operator of the grid, Gradient field The divergence value at the grid vertex.

5. The simulation method for real-time deformation of coal wall in a three-dimensional engine according to claim 2, characterized in that: The process for calculating the deformation at the midpoint of the grid is as follows: set up It is a piecewise linear function, in each triangle of the grid. At the vertex there is Calculated by linear interpolation The value at each point on the triangle is: ； The gradient is as follows: ； in The expression is: ; Calculate in sequence , The expression is given by ⊥, where ⊥ represents rotating the vector counterclockwise by 90 degrees, and A represents the area of ​​the triangle. Let vector-valued function , Represents a grid. The function representing the mapping from vertices to three-dimensional space. Let the vector be the vector on each triangle. At the apex The divergence at a given point is defined as: ； in Represents vertices The 1-ring neighborhood triangle, Represents triangle The area; Substituting the gradient operator expression into the divergence operator expression yields the vertex. The Laplace operator expression at: ； in Indicates the contact point The 1st ring neighboring point, , Let be the opposite angle of edge ij. Smooth the mesh vertices according to the Laplace operator expression at each vertex.

Images