Synchronous updating and real-time rendering method based on tri-dexel model

Abstract

This invention discloses a synchronous update and real-time rendering method based on a tri-dexel model, relating to the fields of computer graphics and CNC machining simulation. First, the workpiece model is initialized, a tri-dexel model is established, and it is converted into voxel data and loaded onto the GPU. During machining, the tri-dexel model is dynamically updated according to the tool path, and the voxel data is synchronized to the GPU. During rendering, a line of sight is projected from the camera to the pixel, and the GPU determines the intersection in parallel. If there is an intersection, the triangular facet is reconstructed and colored; otherwise, the pixel remains uncolored. The synchronous update and real-time rendering method based on a tri-dexel model provided by this invention achieves efficient real-time rendering of high-precision models in dynamic machining, and is applicable to scenarios such as CNC milling and additive manufacturing.

Description

Technical Field

[0001] This invention relates to the fields of computer graphics and CNC machining simulation, and in particular to a synchronous update and real-time rendering method based on the tri-dexel model. Background Technology

[0002] In the fields of computer graphics and CNC machining simulation, the geometry of workpieces changes in real time and in complex ways during CNC milling, additive manufacturing, and other machining processes. Highly realistic and low-latency visualization of these dynamic models is crucial for online monitoring and process optimization. Especially when machining high-value parts, the real-time rendering and model accuracy directly determine the reliability and practicality of the simulation system. Distorted visualization or slow response can mask the actual machining state, leading to flawed process decisions and significant waste of time and resources. Therefore, constructing a smooth, real-time rendering solution that accurately reflects the dynamic changes of the model is essential.

[0003] Current mainstream real-time rendering methods have significant limitations. One type is based on Boolean operations using triangular mesh models. This method incurs a huge computational load when the model topology changes frequently, making it difficult to maintain a high frame rate and meet real-time requirements. It is also extremely unsuitable for scenarios where the model shape continuously evolves during processing. Another type is the traditional voxel method. Although it simplifies the model update logic, it generally suffers from low model accuracy, jagged edges, and extremely high memory consumption. Furthermore, it lacks a general mechanism for efficiently managing and synchronizing voxel data on GPUs, making it difficult to apply to dynamic, high-precision processing scenarios.

[0004] Existing technologies cannot balance dynamic update efficiency, model representation accuracy, and runtime performance, making it difficult to meet the high-precision visualization requirements of arbitrary geometric shapes and dynamic material addition and subtraction processes. Therefore, there is an urgent need for a general real-time rendering method that can fully consider the dynamic changes of the model and directly update voxel data synchronously on the GPU to solve the above-mentioned technical pain points. Summary of the Invention

[0005] The purpose of this invention is to provide a synchronous update and real-time rendering method based on the tri-dexel model, which solves the problem of real-time rendering of high-precision models in dynamic processing scenarios in the existing technology.

[0006] To achieve the above objectives, this invention provides a synchronous update and real-time rendering method based on the tri-dexel model, comprising the following steps:

[0007] Step 1: Initialize the workpiece model, establish the tri-dexel model of the workpiece, convert the tri-dexel model into voxel data, and load it into GPU memory.

[0008] Step 2: In each rendering frame of the machining process, determine the material addition or subtraction area based on the tool path, and perform dynamic update operations on the tri-dexel model. The dynamic update operations include the removal and addition of points.

[0009] Step 3: Immediately synchronize the dynamically updated voxel data to the GPU;

[0010] Step 4: Perform visualization rendering processing, projecting lines of sight from the camera to each pixel on the screen, and determining whether each line of sight intersects with a voxel;

[0011] Step 5: If the judgment result is that the line of sight intersects with the voxel, in the vicinity of the intersection of the line of sight and the voxel, the local triangular facet is reconstructed in real time based on the voxel information, the normal vector and corresponding color of the triangular facet are calculated, and the pixel is colored using the calculation result.

[0012] Step 6: If the result is that the line of sight does not intersect with the voxel, the pixel remains colorless;

[0013] Step 7: Repeat steps 4 to 6 until all pixels on the screen have been processed and the final rendering result is output.

[0014] Preferably, the specific process of establishing the tri-dexel model of the workpiece in step 1 is as follows: load the initial STL file of the workpiece, define the boundary range and sampling interval of the model, calculate the boundary range and triangular facet normal vector of the model, and construct the complete Dexel structure through Dexel Boolean operations in the X, Y and Z directions and three-way Dexel sampling to obtain the tri-dexel model.

[0015] Preferably, the specific process of converting the tri-dexel model into voxel data in step 1 is as follows: establish a three-dimensional voxel grid that matches the Dexel sampling interval, traverse the Dexel data in the X, Y, and Z directions, calculate the coverage of the intersecting line segments on each ray in the voxel space, map the start and end points of the line segments to the corresponding voxel indices, calculate the density values ​​of the voxels, and process the normal vector information to generate 12-channel voxel data containing the density fields in the three directions and the complete normal vector field.

[0016] Preferably, when calculating the density value of a voxel, the UInt8 encoding method is used, which multiplies the floating-point density value in the range of 0-1 by 255 and rounds it up to map it to the integer range of 0-255.

[0017] Preferably, when processing normal vector information, the normal vector is normalized from the floating-point range of [-1, 1] and offset to the range of [0, 1], then converted to UInt8 format for storage, the surface normal vector of the line segment endpoint is assigned to the corresponding boundary voxel, and the normal vector is smoothly transitioned in the surface region through the neighborhood diffusion algorithm.

[0018] Preferably, in step 4, the visualization rendering adopts the voxel-based RayMarching rendering method, which includes GPU data initialization, camera system settings, line-of-sight ray generation, three-dimensional voxel sampling, surface reconstruction and shading, and background color processing.

[0019] Preferably, the specific content of the camera system settings includes: defining the position and orientation of the camera, calculating the view matrix and projection matrix, and setting the near clipping plane and far clipping plane of the camera.

[0020] Preferably, the specific process of generating the line-of-sight ray is as follows: calculate the ray direction corresponding to the pixel, determine the ray starting point and initialize the stepping parameters, and then determine the ray stepping sampling loop. If the loop is determined to be over, the background color is directly processed; otherwise, three-dimensional voxel sampling is performed.

[0021] Preferably, the specific process of three-dimensional voxel sampling is as follows: starting from the near clipping plane, step sampling is performed towards the far clipping plane, the position of the current sampling point is calculated, sampling is performed from the volumeX, volumeY, and volumeZ textures, the density of the sampling point is obtained through trilinear interpolation, a threshold detection is performed on the density, and it is determined whether the density is greater than a preset threshold. If it is, surface reconstruction and shading are performed; otherwise, the judgment of the ray step sampling loop is returned.

[0022] Preferably, the specific content of surface reconstruction and shading is as follows: sampling normal vector texture, combining the viewing direction and light source information, calculating diffuse lighting and specular lighting, and applying preset material and color parameters.

[0023] Therefore, the present invention employs the above-mentioned synchronous update and real-time rendering method based on the tri-dexel model, which has the following beneficial effects:

[0024] (1) Using the voxel-based method based on tri-dexel, and taking advantage of the precise mapping of X, Y and Z three-dimensional Dexel data, we can make full use of the complementary advantages of multi-directional sampling to ensure the accurate reproduction of complex geometric features in voxel space, provide a high-fidelity discretized model for processing simulation, and significantly improve the model representation accuracy.

[0025] (2) Establish a direct voxel update mechanism on the GPU side. After the tri-dexel model is dynamically updated during the processing, the voxel data can be immediately synchronized to the GPU, which greatly reduces the computational load of model update, effectively ensures the real-time performance of rendering, and avoids the problem of low frame rate caused by heavy computational burden in traditional methods.

[0026] (3) By combining RayMarching-based rendering methods with view-driven local surface reconstruction and shading models, and through physical optics cumulative calculation and precise lighting processing, a high-fidelity visualization effect is achieved, avoiding the common edge jaggedness defects of traditional voxel methods and improving rendering quality.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 This is an overall flowchart of the synchronous update and real-time rendering method based on the tri-dexel model of the present invention;

[0029] Figure 2 This is a flowchart of the voxel-based method according to an embodiment of the present invention;

[0030] Figure 3 This is a flowchart of the voxel-based RayMarching rendering process according to an embodiment of the present invention;

[0031] Figure 4 This is a rendering diagram of the tri-dexel sampling data and the voxels converted according to an embodiment of the present invention;

[0032] Figure 5 This is a real-time rendering result obtained using the rendering method in an embodiment of the present invention. Detailed Implementation

[0033] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0034] Please see Figures 1-5 The synchronous update and real-time rendering method based on the tri-dexel model includes the following steps:

[0035] Step 1: Initialize the workpiece model by creating a tri-dexel model. Convert this tri-dexel model into voxel data and load it into GPU memory. The specific process for creating the tri-dexel model is as follows: Load the initial STL file of the workpiece, define the model's boundary range and sampling interval, calculate the model's boundary range and triangular facet normal vectors, and use the two sides of the triangle formed by the three points of each triangular facet in the STL file as vectors to perform a cross product and normalize it to obtain the triangular facet normal vector. During this process, simultaneously confirm the model boundaries and record the geometric maximum values ​​of the entire initial workpiece in each dimension. Through Dexel Boolean operations in the X, Y, and Z directions and three-dimensional Dexel sampling, construct a complete Dexel structure to obtain the tri-dexel model. The specific process of converting the tri-dexel model into voxel data is as follows: A three-dimensional voxel mesh matching the Dexel sampling interval is established. The Dexel data in the X, Y, and Z directions is traversed. For intersecting line segments on each ray, the coverage area in voxel space is calculated using the line segment and voxel interval. This involves mapping the start and end points of the line segment to the corresponding voxel indices, assuming the intermediate voxels are completely filled, and calculating the voxel density value based on the line segment's occupancy ratio in the first and last voxels. If a line segment is located in a single voxel cell, the voxel density value is calculated only based on the line segment's occupancy within that voxel cell. Simultaneously, the normal vector information is processed to generate 12-channel voxel data containing density fields in three directions and a complete normal vector field. When calculating the voxel density value, the UInt8 encoding method is used. Floating-point density values ​​in the 0-1 range are multiplied by 255 and rounded up to map to an integer range of 0-255. When processing normal vector information, the normal vectors are normalized from the floating-point range of [-1, 1] and offset to the range of [0, 1], then converted to UInt8 format for storage. The surface normal vectors of the line segment endpoints are assigned to the corresponding boundary voxels, and a neighborhood diffusion algorithm is used to smoothly transition the normal vectors across the surface region. In general, to ensure the accuracy and efficiency of the workpiece in real-time rendering, a precise conversion method from tri-dexel discrete sampling data to regular voxel meshes is adopted. The tri-dexel structure deploys dense ray beams in the three orthogonal directions of X, Y, and Z, recording the intersection information of the workpiece surface with each ray, including the coordinates of the entry / exit points and the corresponding normal vectors. When calculating the density value of voxels, line segments completely inside the voxel are marked as fully filled (density value 1.0). For partially filled voxel segments that cross voxel boundaries, the precise density value is calculated based on the length ratio of the line segment within the voxel. Using UInt8 encoding, the floating-point density value in the 0-1 range is multiplied by 255 and rounded up to map to an integer range of 0-255. This encoding method significantly reduces storage space requirements while maintaining sufficient accuracy in representing material distribution.Similarly, the normal vector information is normalized from the floating-point range of [-1,1] and offset to [0,1], and finally converted to UInt8 format for storage. The surface normal vectors of the line segment endpoints are directly assigned to the corresponding boundary voxels, and the normal vectors are smoothly transitioned across the surface region through a neighborhood diffusion algorithm. The final generated voxel data contains density fields in three directions and a complete normal vector field, forming a 12-channel voxel representation. Figure 2 The process of this tri-dexel-based voxelization method is shown in detail. This method makes full use of the complementary advantages of multi-directional sampling to ensure the accurate reproduction of complex geometric features in voxel space, providing a high-fidelity discretization model foundation for subsequent processing simulation.

[0036] Step 2: In each rendering frame of the machining process, determine the material addition or subtraction area based on the tool path, and perform dynamic update operations on the tri-dexel model. The dynamic update operations include the removal and addition of points.

[0037] Step 3: Immediately synchronize the dynamically updated voxel data to the GPU;

[0038] Step 4: Perform visualization rendering. A line of sight is projected from the camera to each pixel on the screen, and it is determined whether each line of sight intersects with a voxel. The visualization rendering employs a voxel-based RayMarching rendering method, which includes GPU data initialization, camera system settings, line-of-sight ray generation, three-dimensional voxel sampling, surface reconstruction and shading, and background color processing. Specifically, after the voxel data is loaded into the GPU, high-quality 3D rendering of the workpiece is achieved through precise line-of-sight tracking and sampling calculations. The core principle of this technology is to reproduce a realistic visual representation of the 3D model on the screen through line-of-sight step sampling and physical optics cumulative calculations. The rendering process begins with the virtual camera setup. A line of sight is emitted from the camera position to each pixel on the screen; these rays constitute the basic unit of rendering. Each ray starts from a screen pixel and gradually traverses the pre-constructed voxel mesh space along the line-of-sight direction. In this process, the algorithm adopts a front-to-back sequence, starting from the near clipping plane and performing precise step sampling towards the far clipping plane. In each sampling step, the algorithm meticulously judges the relationship between density and a set threshold. When the density is greater than the set threshold, it uses voxel information near the intersection to reconstruct the mesh. Using normal vectors and other information, the algorithm uses a physically based lighting model, combined with surface normal vectors, view direction, and light source information, to calculate the final color that each pixel should present. Figure 3 This paper demonstrates a physically-based rendering workflow that accurately reproduces complex geometric features and surface details in tri-dexel voxel data, achieving high-quality 3D visualization. The specific steps are as follows:

[0039] The specific details of the camera system settings are as follows: defining the camera's position and orientation, calculating the view matrix and projection matrix, and setting the camera's near and far clipping planes. The view matrix is ​​constructed from the camera's position (eye), the target the camera is looking at, and the camera's up vector. First, the camera's two axis vectors are calculated:

[0040]

[0041]

[0042] Then, the view matrix is:

[0043]

[0044] The projection matrix requires the camera's vertical field of view (fov) in radians, the near distance to the building material plane (near), the far distance to the clipping plane (far), and the screen's aspect ratio (aspect). First, calculate the vertical scaling factor (yScale) and the horizontal scaling factor (xScale):

[0045]

[0046]

[0047] Therefore, the perspective projection matrix is:

[0048]

[0049] The specific process of generating the line-of-sight ray is as follows: calculate the ray direction corresponding to the pixel, determine the ray starting point and initialize the stepping parameters, and then determine the ray stepping sampling loop. If the loop is determined to be over, the background color is processed directly; otherwise, three-dimensional voxel sampling is performed.

[0050] The specific process of three-dimensional voxel sampling is as follows: starting from the near clipping plane, step sampling is performed towards the far clipping plane, the position of the current sampling point is calculated, sampling is performed from the volumeX, volumeY, and volumeZ textures, the density of the sampling point is obtained through trilinear interpolation, a threshold detection is performed on the density to determine whether the density is greater than the preset threshold. If it is, surface reconstruction and shading are performed; otherwise, the judgment of the ray step sampling loop is returned.

[0051] The specific content of surface reconstruction and shading is as follows: sample normal vector texture, combine view direction and light source information, calculate lighting, and apply preset material and color parameters.

[0052] Ambient light simulates global, uniform illumination in a scene, independent of the position of the light source and the orientation of objects. The formula for calculating ambient light is as follows:

[0053]

[0054] in: It is the color intensity of ambient light. It is the ambient light reflectance of an object, and its value usually ranges from 100 to 1000. Between these two values, it indicates an object's ability to reflect ambient light. It refers to the color intensity of ambient light.

[0055] Diffuse reflection simulates the uniform scattering of light on an object's surface; it depends on the angle between the direction of the light rays and the normal to the object's surface. Its formula is:

[0056]

[0057] in: It is the color intensity of diffuse reflected light. It is the diffuse reflectance coefficient of an object, and its value usually ranges from 100 to 1000. Between these two values, it represents an object's ability to reflect diffuse light. Where N is the color intensity of the light source, N is the unit normal vector of the object's surface, and L is the unit vector from the object's surface to the light source. It is the dot product of N and L. Ensure the result is not negative.

[0058] Specular reflection simulates the effect of light reflecting off a surface, and its accuracy depends on the observer's position. The formula for calculating specular reflection is as follows:

[0059]

[0060] in: It is the color intensity of the light reflected from the specular surface. It is the specular reflection coefficient of an object, and its value usually ranges from 100 to 1000. Between these two values, it indicates an object's ability to reflect specularly reflected light. R is the color intensity of the light source, and R is the unit vector of the reflected light. This can be expressed by the formula... The calculated value is V, which is a unit vector pointing from the object's surface to the observer. It is the specular coefficient, which controls the range of specular reflection. The larger the value, the more concentrated the highlights.

[0061] The final color of the light is the sum of ambient light, diffuse light, and specular light:

[0062]

[0063] Step 5: If the judgment result is that the line of sight intersects with the voxel, in the vicinity of the intersection of the line of sight and the voxel, the local triangular facet is reconstructed in real time based on the voxel information, the normal vector and corresponding color of the triangular facet are calculated, and the pixel is colored using the calculation result.

[0064] Step 6: If the result is that the line of sight does not intersect with the voxel, the pixel remains colorless;

[0065] Step 7: Repeat steps 4 to 6 until all pixels on the screen have been processed and the final rendering result is output.

[0066] Figure 4 This case study demonstrates the rendering effect of tri-dexel sampling data and the resulting voxels. It shows the instantaneous tri-dexel sampling effect and the calculation and reconstruction effect of the surface normal field at a certain moment during the machining of a rectangular workpiece, as well as the rendering effect after real-time modification of the workpiece voxels in the GPU memory. Figure 5 This demonstration showcases the real-time rendering results obtained using this rendering method for complex surface workpieces. A ball-end milling cutter was selected to machine a rectangular workpiece using a helical feed method to obtain a relatively complex workpiece surface morphology. A size of [missing information - likely a specific dimension] was chosen. A rectangular workpiece is machined on one side using a ball end mill with a radius of 4mm. The tool path is as follows:

[0067] ;

[0068] This allows for the creation of a surface of varying depth on the side of the rectangle. The rendering method is then used to render the surface, demonstrating its high accuracy and rendering effect when dealing with workpieces with complex geometries.

[0069] Therefore, the synchronous update and real-time rendering method based on the tri-dexel model adopted in this invention has the advantages of high rendering efficiency, fast model update, and high-precision real-time visualization of any complex geometric shape and dynamic material addition and subtraction process. It is especially suitable for complex scenarios where the workpiece shape continuously evolves in processes such as five-axis CNC milling and additive manufacturing. It has important value for online monitoring of the machining process, process planning optimization and virtual debugging.

[0070] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A synchronous update and real-time rendering method based on the tri-dexel model, characterized in that, Includes the following steps: Step 1: Initialize the workpiece model, establish the tri-dexel model of the workpiece, convert the tri-dexel model into voxel data, and load it into GPU memory. Step 2: In each rendering frame of the machining process, determine the material addition or subtraction area based on the tool path, and perform dynamic update operations on the tri-dexel model. The dynamic update operations include the removal and addition of points. Step 3: Immediately synchronize the dynamically updated voxel data to the GPU; Step 4: Perform visualization rendering processing, projecting lines of sight from the camera to each pixel on the screen, and determining whether each line of sight intersects with a voxel; Step 5: If the judgment result is that the line of sight intersects with the voxel, in the vicinity of the intersection of the line of sight and the voxel, the local triangular facet is reconstructed in real time based on the voxel information, the normal vector and corresponding color of the triangular facet are calculated, and the pixel is colored using the calculation result. Step 6: If the result is that the line of sight does not intersect with the voxel, the pixel remains colorless; Step 7: Repeat steps 4 to 6 until all pixels on the screen have been processed and output the final rendering result; The specific process of establishing the tri-dexel model of the workpiece in step 1 is as follows: load the initial STL file of the workpiece, define the boundary range and sampling interval of the model, calculate the boundary range and triangular face normal vector of the model, and construct the complete Dexel structure through Dexel Boolean operations and three-dimensional Dexel sampling in the X, Y and Z directions to obtain the tri-dexel model. The specific process of converting the tri-dexel model into voxel data in step 1 is as follows: establish a three-dimensional voxel grid that matches the Dexel sampling interval, traverse the Dexel data in the X, Y, and Z directions, calculate the coverage of the intersecting line segments on each ray in the voxel space, map the start and end points of the line segments to the corresponding voxel indices, calculate the density values ​​of the voxels, and process the normal vector information to generate 12-channel voxel data containing the density fields in the three directions and the complete normal vector field. When calculating the density value of a voxel, the UInt8 encoding method is used. The floating-point density value in the range of 0-1 is multiplied by 255 and rounded up to map to the integer range of 0-255. When processing normal vector information, the normal vector is normalized from the floating-point range of [-1, 1] and offset to the range of [0, 1], and then converted to UInt8 format for storage. The surface normal vectors of the line segment endpoints are assigned to the corresponding boundary voxels, and the normal vectors are smoothly transitioned in the surface region through the neighborhood diffusion algorithm.

2. The synchronous update and real-time rendering method based on the tri-dexel model according to claim 1, characterized in that: In step 4, the visualization rendering adopts the voxel-based RayMarching rendering method, which includes GPU data initialization, camera system settings, line-of-sight ray generation, three-dimensional voxel sampling, surface reconstruction and shading, and background color processing.

3. The synchronous update and real-time rendering method based on the tri-dexel model according to claim 2, characterized in that: The specific content of the camera system settings includes: defining the camera's position and orientation, calculating the view matrix and projection matrix, and setting the camera's near clipping plane and far clipping plane.

4. The synchronous update and real-time rendering method based on the tri-dexel model according to claim 3, characterized in that, The specific process of generating the line-of-sight ray is as follows: calculate the ray direction corresponding to the pixel, determine the ray starting point and initialize the stepping parameters, and then determine the ray stepping sampling loop. If the loop is determined to be over, the background color is processed directly; otherwise, three-dimensional voxel sampling is performed.

5. The synchronous update and real-time rendering method based on the tri-dexel model according to claim 4, characterized in that, The specific process of three-dimensional voxel sampling is as follows: starting from the near clipping plane, step sampling is performed towards the far clipping plane, the position of the current sampling point is calculated, sampling is performed from the volumeX, volumeY, and volumeZ textures, the density of the sampling point is obtained through trilinear interpolation, a threshold detection is performed on the density to determine whether the density is greater than the preset threshold. If it is, surface reconstruction and shading are performed; otherwise, the judgment of the ray step sampling loop is returned.

6. The synchronous update and real-time rendering method based on the tri-dexel model according to claim 5, characterized in that, The specific content of surface reconstruction and shading is as follows: sample normal vector texture, combine view direction and light source information, calculate diffuse lighting and specular lighting, and apply preset material and color parameters.

Images