SOFTWARE DEVELOPMENT FOR RENDERING THREE-DIMENSIONAL SURFACES IN A WEB BROWSER

Представлена реализация программного обеспечения для построения трехмерных поверхностей с использованием трассировки лучей, выполняемого в веб-браузере персонального компьютера или смартфона. Подход веб-приложений стал широко применим в последние годы из-за развития сети Интернет. Современные веб-браузеры имеют достаточную вычислительную мощность для реализации сложных веб-приложений, а не ограничиваются только веб-сайтами. В процессе разработки были изучены различные методы построения поверхностей и методы визуализации, чтобы подобрать наиболее оптимальные для реализации веб-приложения. Были проанализированы и представлены базовые способы создания трехмерных поверхностей. Выделены ключевые различия каркасного и полигонального способа задания поверхности. Рассмотрен ряд моделей с процедурно вычисляемыми поверхностями. Подробно описан кинематический способ образования поверхностей, а также описан разработанный алгоритм для преобразования кинематических моделей в поверхность с использованием полигональной сетки. Подробно описан процесс визуализации и метод трассировки лучей. Продемонстрирован способ работы с видеочипом и распараллеливанию вычислений для оптимизации веб-приложения с помощью библиотеки GPU.js. Представлена структура веб-приложения с описанием главных каталогов проекта. Структура проекта основана на фреймворке Vue.js, благодаря чему функционал веб-приложения позволяет безгранично расширять. Для демонстрации работы веб-приложения представлен пример пошагового задания кинематической поверхности и визуализации на сцене с применением графических эффектов, таких как закраска и освещение, а также представлен пример с визуализацией множества объектов на сцене The article presents the implementation of software for rendering 3D-surfaces using ray tracing, running in a web browser of computers or smartphones. The web application approach has become widespread in recent years due to the development of the Internet. Modern web browsers have enough processing power to run complex web applications and are not limited to just websites. During the development process, various methods for constructing surfaces and visualization methods were analyzed to choose the most optimal solution for web applications. We analyzed and presented basic methods of creating 3D surfaces. We highlighted the key differences between wireframe and polygonal methods of surface definition. We considered several models with dynamic surface computation. We described the kinematic method of surface formation in detail and the developed algorithm for transforming kinematic models into a surface using a polygonal mesh. We described in detail the rendering process and ray tracing method. We demonstrated a way of working with a video chip and parallelizing computations to optimize a web application using the GPU.js library. We presented the structure of a web application with a description of the main project directories. The project structure is based on the Vue.js framework. The framework allows one to endlessly expand the functionality of a web application. The article presents how the web application works and example of step-by-step creation of a kinematic surface and rendering on a scene using graphic effects such as shading and lighting. Also it contains an example of rendering many objects on a scene

Free and Forced Vibration Analysis in Abaqus Based on the Polygonal Scaled Boundary Finite Element Method

The polygonal scaled boundary finite element method (PSBFEM) is a novel approach integrating the standard scaled boundary finite element method and the polygonal mesh technique. In this work, a user-defined element (UEL) for dynamic analysis based on the PSBFEM is developed in the general finite element software ABAQUS. We present the main procedures of interacting with Abaqus, updating AMATRX and RHS, defining the UEL element, and solving the stiffness and mass matrices through eigenvalue decomposition. Several benchmark problems of free and forced vibration are solved to validate the proposed implementation. The results show that the PSBFEM is more accurate than the FEM with mesh refinement. Moreover, the PSBFEM avoids the occurrence of hanging nodes by constructing a polygonal mesh. Thus, the PSBFEM can choose an appropriate mesh resolution for different structures ensuring accuracy and reducing calculation costs.

Coupling BEM and VEM for the Analysis of Composite Materials with Damage

Numerical tools which are able to predict and explain the initiation and propagation of damage at the microscopic level in heterogeneous materials are of high interest for the analysis and design of modern materials. In this contribution, we report the application of a recently developed numerical scheme based on the coupling between the Virtual Element Method (VEM) and the Boundary Element Method (BEM) within the framework of continuum damage mechanics (CDM) to analyze the progressive loss of material integrity in heterogeneous materials with complex microstructures. VEM is a novel numerical technique that, allowing the use of general polygonal mesh elements, assures conspicuous simplification in the data preparation stage of the analysis, notably for computational micro-mechanics problems, whose analysis domain often features elaborate geometries. BEM is a widely adopted and efficient numerical technique that, due to its underlying formulation, allows reducing the problem dimensionality, resulting in substantial simplification of the pre-processing stage and in the decrease of the computational effort without affecting the solution accuracy. The implemented technique has been applied to an artificial microstructure, consisting of the transverse section of a circular shaped stiff inclusion embedded in a softer matrix. BEM is used to model the inclusion that is supposed to behave within the linear elastic range, while VEM is used to model the surrounding matrix material, developing more complex nonlinear behaviors. Numerical results are reported and discussed to validate the proposed method.

A Blind Watermarking Model of the 3D Object and the Polygonal Mesh Objects for Securing Copyright

In this paper, we propose a novel model for 3D object watermarking. The proposed method is based on the properties of the discrete cosine transform (DCT) of the 3D object vertices to embed a secret grayscale image three times. The watermarking process takes place by using the vertices coefficients and the encrypted image pixels. Moreover, the extraction process is totally blind based on the reverse steps of the embedding process to recover the secret grayscale image. Various performance aspects of the method are measured and compared between the original 3D object and the watermarked one using Euclidean distance, Manhattan distance, cosine distance, and correlation distance. The obtained results show that the proposed model provides better performances in terms of execution time and invisibility.

Geodesic Hermite Spline Curve on Triangular Meshes

Curves on a polygonal mesh are quite useful for geometric modeling and processing such as mesh-cutting and segmentation. In this paper, an effective method for constructing C1 piecewise cubic curves on a triangular mesh M while interpolating the given mesh points is presented. The conventional Hermite interpolation method is extended such that the generated curve lies on M. For this, a geodesic vector is defined as a straightest geodesic with symmetric property on edge intersections and mesh vertices, and the related geodesic operations between points and vectors on M are defined. By combining cubic Hermite interpolation and newly devised geodesic operations, a geodesic Hermite spline curve is constructed on a triangular mesh. The method follows the basic steps of the conventional Hermite interpolation process, except that the operations between the points and vectors are replaced with the geodesic. The effectiveness of the method is demonstrated by designing several sophisticated curves on triangular meshes and applying them to various applications, such as mesh-cutting, segmentation, and simulation.

Automatic Reconstruction of Building Façade Model from Photogrammetric Mesh Model

Three-dimensional (3D) building façade model reconstruction is of great significance in urban applications and real-world visualization. This paper presents a newly developed method for automatically generating a 3D regular building façade model from the photogrammetric mesh model. To this end, the contour is tracked on irregular triangulation, and then the local contour tree method based on the topological relationship is employed to represent the topological structure of the photogrammetric mesh model. Subsequently, the segmented contour groups are found by analyzing the topological relationship of the contours, and the original mesh model is divided into various components from bottom to top through the iteration process. After that, each component is iteratively and robustly abstracted into cuboids. Finally, the parameters of each cuboid are adjusted to be close to the original mesh model, and a lightweight polygonal mesh model is taken from the adjusted cuboid. Typical buildings and a whole scene of photogrammetric mesh models are exploited to assess the proposed method quantitatively and qualitatively. The obtained results reveal that the proposed method can derive a regular façade model from a photogrammetric mesh model with a certain accuracy.

PSBFEM-Abaqus: Development of User Element Subroutine (UEL) for Polygonal Scaled Boundary Finite Element Method in Abaqus

The polygonal scaled boundary finite element method (PSBFEM) is a novel method integrating the standard scaled boundary finite element method (SBFEM) and the polygonal mesh technique. This work discusses developing a PSBFEM framework within the commercial finite element software Abaqus. The PSBFEM is implemented by the User Element Subroutine (UEL) feature of the software. The details on the main procedures to interact with Abaqus, defining the UEL element, and solving the stiffness matrix by the eigenvalue decomposition are present. Moreover, we also develop the preprocessing module and the postprocessing module using the Python script to generate meshes automatically and visualize results. Several benchmark problems from two-dimensional linear elastostatics are solved to validate the proposed implementation. The results show that PSBFEM-UEL has significantly better than FEM convergence and accuracy rate with mesh refinement. The implementation of PSBFEM-UEL can conveniently use arbitrary polygon elements by the polygon/quadtree discretizations in the Abaqus. The developed UEL and the associated input files can be downloaded from https://github.com/hhupde/PSBFEM-Abaqus.

A Polygonal Scaled Boundary Finite Element Method for Solving Heat Conduction Problems

This paper presents a steady-state and transient heat conduction analysis framework using the polygonal scaled boundary finite element method (PSBFEM) with polygon/quadtree meshes. The PSBFEM is implemented with commercial finite element code Abaqus by the User Element Subroutine (UEL) feature. The detailed implementation of the framework, defining the UEL element, and solving the stiffness/mass matrix by the eigenvalue decomposition are presented. Several benchmark problems from heat conduction are solved to validate the proposed implementation. Results show that the PSBFEM is reliable and accurate for solving heat conduction problems. Not only can the proposed implementation help engineering practitioners analyze the heat conduction problem using polygonal mesh in Abaqus, but it also provides a reference for developing the UEL to solve other problems using the scaled boundary finite element method.

A PLATFORM FOR MULTILAYERED DOCUMENTATION OF CULTURAL HERITAGE

This paper presents a platform for multilayered documentation of cultural heritage, inspired by the current lack of a heritage BIM approach capable of creating models with both high geometric accuracy and high semantic richness. The platform is developed in the Unity game engine. It comprises several integrated and interconnected layers or datasets that can include data of different types, such as a point cloud, textured polygonal mesh, parametric information model and images, both 2D images and 360° panoramas. We present an overview of the platform concept, the benefits of the proposed multilayered representation and the details on the implementation and integration of datasets. Also, we present some of the innovative functions made possible by this integration, such as point cloud or mesh cutting and preforming measurements on 2D images and 360° panoramas. We perform and present the results of a preliminary analysis of platform functions, which indicates that the platform can be used for accurate measurement and retrieval of 3D coordinates.

3D Simulation Workflow for Performance of Sharp and Worn PDC Drill Bits

This paper describes the development of an improved polycrystalline diamond cutter (PDC) drilling performance simulation in 3D which includes worn cutters. A polygonal mesh model is used to improve the geometric data needed for the drilling performance model calculations. Methods for active face identification have been developed to consistently identify a variety of polygonal face types. The simple wear flat definition used for data input is shown to adequately capture the geometry compared to field worn bit scans and provide valuable insights with active face identification. Drilling performance calculation and results from the calibration to laboratory drilling data and validation to both laboratory and field data are shown. Additionally, including a velocity parameter in the drilling performance model reduced model error.