Polygonal Models Research Articles

Lightweight Design of Aircraft Virtual Scene and Wireless Transmission

The concept of virtual reality, which is an important role in aircraft simulation training, was first proposed in the aerospace field in the 1960s. In recent years, with the development of hardware technology, virtual reality technology has been widely used in games, entertainment, medical and other civilian fields. In the field of civil aircraft, virtual reality technology mainly focuses on simulated flight, cockpit pilot training, aircraft maintenance training, etc. This article proposes a customer-oriented aircraft virtual scene design and implementation method, and describes the design process from aircraft 3D model construction, lightweight processing, virtual scene rendering, and WebRTC-based wireless video streaming. The main technical difficulties solved in this paper include two parts: one is to convert the existing aircraft 3D engineering model into a polygonal model that can be used for VR rendering, and the other is to realize the problem of multi-user online interactive access to virtual scenes. Through this system, users can do engineering evaluation and experience evaluation during the whole process of aircraft product design, development and sales. The application scenarios designed in this paper further expand the application of virtual reality technology in the field of civil aircraft development and lay the foundation for the development of more application scenarios in the future.

Development of Integrated 3-Dimensional Computer Graphics Human Head Model

Understanding the complex anatomy of neurostructures is very important in various stages of medical education, from medical students to experienced neurosurgeons, and, ultimately, for the knowledge of human beings. To develop an interactive computer graphics (CG) anatomic head model and present the current progress. Based on the prior head 3-dimensional CG (3DCG) polygon model, 23 additional published papers and textbooks were consulted, and 2 neurosurgeons and 1 CG technician performed revision and additional polygon modeling. Three independent neurosurgeons scored the clear visibility of anatomic structures relevant to neurosurgical procedures (anterior petrosal and supracerebellar infratentorial approaches) in the integrated 3DCG model (i model) and patients' radiological images (PRIs) such as those obtained from computed tomography, magnetic resonance imaging, and angiography. The i model consisted of 1155 parts (.stl format), with a total of 313 763 375 polygons, including 10 times more information than the foundation model. The i model was able to illustrate complex and minute neuroanatomic structures that PRIs could not as well as extracranial structures such as paranasal sinuses. Our subjective analysis showed that the i model had better clear visibility scores than PRIs, particularly in minute nerves, vasculatures, and dural structures. The i model more clearly illustrates minute anatomic structures than PRIs and uniquely illustrates nuclei and fibers that radiological images do not. The i model complements cadaveric dissection by increasing accessibility according to spatial, financial, ethical, and social aspects and can contribute to future medical education.

ANALYTICAL APPROACH IN DRAWING IN ARCHITECTURAL EDUCATION

Drawing is one of the vital tools of creative process for an architect. It helps to generate an idea. Work on image of a future building starts with it. Teaching drawing is one of the most important stages in comprehensive specialized training of architecture students. So the purpose of this article is the essence of analytical approach in drawing. And its tasks are to analyze basic types of drawing, to reveal the essence of shape making and analytical approach in drawing in architects; to uncover the meaning of basic methods of constructive drawing; to outline the place of constructive drawing in development of an architect’s professional competencies. Techniques for creating a shape of an object on a plane largely depend on its structure. Therefore, when analyzing a shape of an object, one should start with an insight into the essence of its inner structure, disregarding small details, which prevent one from understanding geometric base of its construction. This will enable students to get more comprehensive information about the object and to create a drawing deliberately. Construction in fine arts means the essence, distinguishing feature of a structure of any shape, implying interrelation of parts in the whole and their correlation. When analyzing basic types of drawing in our research, we study linear constructive (linear) drawing, linear constructive drawing with conditional light-and-shadow, light-and-shadow drawing, tonal drawing. Teaching architecture students academic drawing should be based on structural constructive drawing, also known as linear constructive drawing. Key task in teaching drawing is to learn to see three-dimensional shape of an object correctly and to be able to depict it in a logical sequence on a plane of a sheet of paper. Shape of an object shall mean geometric essence of the surface of the object, characterizing its exterior. Hence, any object is a shape, and a shape means volume. Shape modelling suggested by A. P. Chistov is based on the following methods: modelling of a complex shape (Boolean modelling), polygonal modelling, curve modelling (spline modelling), tonal modelling, symmetrical shape modelling, and dynamic modelling.

Spatial function of light in staging of contemporary choreography

The principles of using light in choreographic performances are the basis of image perception integrity. The novelty of the study is determined by the fact that the illumination as a component of the performance can be based not only on the physical laws of light, but also on its imitation. To look into the matter of illumination, the authors consider it necessary to use a polygonal model, which can also form a spatial picture if necessary. The paper defines the general illumination model, which uses ray tracing technology and allows to determine the structure of lighting in the hall and to distribute the light to understand the director's intention among the entire visual sector. The practical significance of the study is determined by the structure of using lighting as part of staging choreography in the postmodern genre.

Endoscopic Transorbital Approaches to Anterior and Middle Cranial Fossa: Exploring the Potentialities of a Modified Lateral Retrocanthal Approach

Among the new perspectives to revolutionize skull base surgery, there are the transorbital neuroendoscopic (TONES) approaches to reach the anterior and middle cranial fossa (ACF and MCF). We conceived to explore the potentialities of a modified superiorly and medially extended lateral retrocanthal (LRC) approach. Six head specimens were dissected. Applying the established conic model and the key surgical landmark of sphenofrontal suture, we tested the feasibility of a modified LRC to reach ACF and MCF; computed tomography (CT) scans were performed before and after dissection to obtain a morphometric analysis of the surgical corridors using a polygonal surfaces model. Through our anatomical study, we were able to identify and explore 3 different surgical corridors to reach the ACF and MCF: the superomedial, the superolateral, and the inferolateral. The superomedial corridor appeared most suitable to reach the medial part of the ACF and the optic-carotid region, whereas through the superolateral and inferolateral corridors it was possible to reach and explore the lateral part of ACF and MCF. The mean volumes of the 3 surgical corridors calculated on post-dissection CT scans were: 12.72 ± 1.99, 5.69 ± 0.34, and 6.24 ± 0.47 cm3, respectively. The development of TONES approaches has not replaced the traditional open or endoscopic approach; nonetheless, identification of surgical corridors and the possibility to combine them represent a major breakthrough. Clinical studies are necessary to demonstrate their validity and test the effectiveness, safety, and reproducibility of TONES approaches in managing lesions harboring in the ACF and MCF.

Development of an algorithm for effective design of respirator half-masks and encapsulated particle filters

Objective. Social and economic situations in the modern world require new approaches to the development of respiratory protective equipment. This study aimed to improve the three-dimensional modeling process for respirator half-masks and encapsulated particle filters. Methods. Basic provisions of the theory of non-stationary filtration and hydroaerodynamics, the Nelder–Mead method and the linear interpolation equation were used. Results. The peculiarity of the algorithm is the adjustment stage of the design process aimed at checking efficiency of the half-mask. The surface of the half-mask was constructed according to the coordinates of a three-dimensional model of a worker’s head. Conclusion. For the first time, the regularities of an algorithm for designing the half-mask surface of dust respirators were defined based on the data for three-dimensional coordinates of key points of anthropometric parameters of workers’ faces. The pressure difference on the encapsulated particle filters of dust respirators is determined by the particle filter’s resistance coefficient and air flow through them, and the diameter ratio of their outlets and inlets. The developed algorithm provides product verification at the design stage using criteria evaluating parameters of a polygonal model of the head, preliminary calculation of the protection factor and checking the tightness of the prototype.

Consistent decentralized cooperative localization for autonomous vehicles using LiDAR, GNSS, and HD maps

AbstractTo navigate autonomously, a vehicle must be able to localize itself with respect to its driving environment and the vehicles with which it interacts. This study presents a decentralized cooperative localization method. It is based on the exchange of local dynamic maps (LDM), which are cyber‐physical representations of the physical driving environment containing poses and kinematic information about nearby vehicles. An LDM acts as an abstraction layer that makes the cooperation framework sensor‐agnostic, and it can even improve the localization of a sensorless communicating vehicle. With this goal in mind, this study focuses on the property of consistency in LDM estimates. Uncertainty in the estimates needs to be properly modeled, so that the estimation error can be statistically bounded for a given confidence level. To obtain a consistent system, we first introduce a decentralized fusion framework that can cope with LDMs whose errors have an unknown degree of correlation. Second, we present a consistent method for estimating the relative pose between vehicles, using a two‐dimensional LiDAR (light detection and ranging) with a point‐to‐line metric within an iterative‐closest‐point approach, combined with communicated polygonal shape models. Finally, we add a bias estimator to reduce position errors when nondifferential GNSS (global navigation satellite system) receivers are used, based on visual observations of features geo‐referenced in a high‐definition map. Real experiments were conducted, and the consistency of our approach was demonstrated on a platooning scenario using two experimental vehicles. The full experimental data set used in this study is publicly available.

A Polygonal Model to Design and Fabricate Ion-Exchanged Diffraction Gratings

We propose a simple polygonal model to describe the phase profile of ion-exchanged gratings. This model enables the design of these gratings, as well as the characterization of the ion-exchange process itself. Several ion-exchanged gratings were fabricated to validate the model and to characterize the process involved in their fabrication. From this characterization, we show the practical utility of the model by designing and fabricating both a grating that removes the zero order and a three splitter. The performance of these two elements was good, although the first one stood out especially because only 0.5% of the power remained in the zero order after diffraction. This polygonal model could be useful to design more complex diffractive elements.

A Comparative Study about Data Structures Used for Efficient Management of Voxelised Full-Waveform Airborne LiDAR Data during 3D Polygonal Model Creation

In this paper, we investigate the performance of six data structures for managing voxelised full-waveform airborne LiDAR data during 3D polygonal model creation. While full-waveform LiDAR data has been available for over a decade, extraction of peak points is the most widely used approach of interpreting them. The increased information stored within the waveform data makes interpretation and handling difficult. It is, therefore, important to research which data structures are more appropriate for storing and interpreting the data. In this paper, we investigate the performance of six data structures while voxelising and interpreting full-waveform LiDAR data for 3D polygonal model creation. The data structures are tested in terms of time efficiency and memory consumption during run-time and are the following: (1) 1D-Array that guarantees coherent memory allocation, (2) Voxel Hashing, which uses a hash table for storing the intensity values (3) Octree (4) Integral Volumes that allows finding the sum of any cuboid area in constant time, (5) Octree Max/Min, which is an upgraded octree and (6) Integral Octree, which is proposed here and it is an attempt to combine the benefits of octrees and Integral Volumes. In this paper, it is shown that Integral Volumes is the more time efficient data structure but it requires the most memory allocation. Furthermore, 1D-Array and Integral Volumes require the allocation of coherent space in memory including the empty voxels, while Voxel Hashing and the octree related data structures do not require to allocate memory for empty voxels. These data structures, therefore, and as shown in the test conducted, allocate less memory. To sum up, there is a need to investigate how the LiDAR data are stored in memory. Each tested data structure has different benefits and downsides; therefore, each application should be examined individually.

Counting walks by their last erased self-avoiding polygons using sieves

Let G be an infinite, vertex-transitive lattice with degree λ and fix a vertex on it. Consider all cycles of length exactly l from this vertex to itself on G. Erasing loops chronologically from these cycles, what is the fraction Fp∕λℓ(p) of cycles of length l whose last erased loop is some chosen self-avoiding polygon p of length ℓ(p), when l→∞ ? We use combinatorial sieves to prove an exact formula for Fp∕λℓ(p) that we evaluate explicitly. We further prove that for all self-avoiding polygons p, Fp∈Q[χ] with χ an irrational number depending on the lattice, e.g. χ=1∕π on the infinite square lattice. In stark contrast we current methods, we proceed via purely deterministic arguments relying on Viennot’s theory of heaps of pieces seen as a semi-commutative extension of number theory. Our approach also sheds light on the origin of the difference between exponents stemming from loop-erased walk and self-avoiding polygon models, and suggests a natural route to bridge the gap between both.

Procedural Animation of Freshly Cooked Rice Based on Water Content-Aware XPBD and CDRF Shader

In this paper, we propose a method of reproducing freshly cooked rice using computer graphics animation. The physical properties of freshly cooked rice (rice grains) include shape, density, refractive index, transmittance, and reflectance. Based on these data, the objective is to render the texture and shape of a large amount of cooked rice in a photo-realistic way. Create rice grain polygon models with low resolution based on electron micrographs, rice grains with different shapes and considering the porous structure, we can create a large number of 3D rice grain models. Next, a large number of freshly cooked rice grains were transferred to XPBD (eXtended Position-Based Dynamics), we simulate aggregates by adding a constraint condition. This can be used to simulate the softness of freshly cooked rice. It also allows you to create any shape of rice structure. Finally, the Sub-Surface Scattering (SSS) also takes into account the water content, so that it can be used for the Curvature-dependent reflectance function (CDRF). Depending on the moisture content, different rice grains can be represented with different appearances. With such proposed method, a large number of rice grains are placed in a bowl of freshly cooked rice, rice balls, sushi rice, etc. is represented realistically.

Three-Dimensional Analysis of Soft and Hard Tissue Changes following Orthognathic Surgery

Change in soft tissue in relation to that in hard tissue following orthognathic surgery was evaluated. Twenty-five patients were enrolled in the study. The diagnosis in all was jaw deformity (maxillary retrusion and mandibular protrusion) and all underwent a Le Fort I osteotomy and bilateral sagittal splitting ramus osteotomy. Three-dimensional (3D) computer-aided design (CAD) models (polygon models) of the hard and soft tissue of the maxilla and mandible were constructed and superimposed. Reference points were established on the pre- and postoperative hard and soft tissues. Specific elements of each reference point were divided into X, Y, and Z components, respectively, and the distances in each direction and 3D distance (normal distance) measured. The Wilcoxon signed-rank test was used to determine differences in the mean values for the distance moved of each element as the error between pre- and postoperatively. The results revealed statistically significant differences in the Y-direction in the maxilla and the X- and Z-directions in the mandible. A significant difference was also observed in the 3D distances of the maxilla and mandible. Little evidence was found of linearity between the amount of hard and soft tissue movement in the X- and Z-directions in the maxilla. This means that 3D movement in the maxilla was masked more by changes in the morphology of the soft tissue than in the mandible, making it less evident. The results of this study suggest that the 3D analysis method used enables changes in hard and soft tissues to be understood qualitatively, and that it can be used in diagnosis and treatment in orthognathic surgery. It may also be useful in simulation of morphological change in soft tissue.

FRACTAL SURFACE INTERPOLATION BASED ON CLASSICAL SUBDIVISION SCHEMES

A method to create a differentiable complex shapes from simple polygonal models is proposed. It is shown that classical schemes of “smooth” subdivision can be obtained from local self-similarity ratios if “deflection arrows” are scaled as s2, where s is the linear compression coefficient calculated for a flat regular grid of the same structure. The surfaces obtained by a smooth subdivision do not contain sharp features other than the vertices and edges of the original model, so in order to create a surface of more exotic shape one must use more complex model. The article describes an alternative approach, in which a fractal forecast of the position of embedded vertices, calculated using the local geometric self-similarity ratio, is used to obtain a pronounced surface shape. Fractal forecast transfers the properties of the original polygonal model to a smaller scale, thereby generating secondary sharp surface features that compose a large-scale texture. To ensure the differentiability of the surface, the fractal forecast is combined with the “smooth” one, and the proportion of the latter increases with decreasing scale.

CREATING A THREE-DIMENSIONAL MODEL OF THE TERRAIN BASED ON THE SURVEY DATA FROM AN UNMANNED AERIAL VEHICLE

. Today, three-dimensional models of objects and terrain are a very popular product and are found almost everywhere in our life: in the gaming and film industries, in various industries and complex technological areas such as architecture, construction, medicine, etc. The article considers the creation of a three-dimensional terrain model based on data obtained from an unmanned aerial vehicle to the territory of an aluminum alloy plant located in the city of Podolsk (Lviv microdistrict), Moscow region. The initial data for processing were obtained by a passive aerial survey method – the Phantom 4 PRO apparatus. The main part of the article is devoted to the stages of processing in the Agisoft Metashape software, which include such processes as: importing and aligning the position of cameras (as well as their optimization); building a sparse and dense point cloud; reconstruction of a polygonal three-dimensional terrain model; applying a texture created on the basis of images;optimization of the model and consideration of possible formats for export to third-party software. As a result of the work, a three-dimensional terrain model was obtained with an accuracy of binding to the centers of images of 1.14 m. The time spent on processing the survey data from an unmanned aerial vehicle is no more than 5 hours.

Cyclic response of a reinforced concrete frame: Comparison of experimental results with different hysteretic models

<abstract> <p>An accurate hysteresis model is fundamental to well capture the non-linearity phenomena occurring in structural and non-structural elements in building structures, that are usually made of reinforced concrete or steel materials. In this sense, this paper aims to numerically estimate through simplified non-linear analyses, the cyclic response of a reinforced concrete frame using different hysteretic models present in the literature. A commercial Finite Element Method package is used to carry out most of the simulations using polygonal hysteretic models and a fiber model, and additionally, a MATLAB script is developed to use a smooth hysteresis model. The experimental data is based on the experiments carried out in the Laboratório Nacional de Engenharia Civil, Portugal. The numerical outcomes are further compared with the experimental result to evaluate the accuracy of the simplified analysis based on the lumped plasticity or plastic hinge method for the reinforced concrete bare frame. Results show that the tetralinear Takeda's model fits closely the experimental hysteresis loops. The fiber model can well capture the hysteresis behavior, though it requires knowledge and expertise on parameter calibration. Sivaselvan and Reinhorn's smooth hysteresis model was able to satisfactorily reproduce the actual non-linear cyclic behavior of the RC frame structure in a global way.</p> </abstract>

АНИМАЦИОННАЯ ТРЕХМЕРНАЯ МОДЕЛЬ АМУРСКОГО КАЗАКА XVII ВЕКА

The stages of modeling a historically accurate character are considered, from recreating the human body and clothing from sketches to optimizing and baking a highly polygonal model onto a texture.

ВИКОРИСТАННЯ ТРИВИМІРНОГО МОДЕЛЮВАННЯ ДЛЯ ВИЗНАЧЕННЯ МАСО-ВАГОВИХ ХАРАКТЕРИСТИК ЛЮДИНИ ПО ЇЇ АНТРОПОМЕТРИЧНИМ ПАРАМЕТРАМ

Тривимірні моделі людини є найреалістичнішими, відображають анатомічну структуру, точно передають рельєфні та кольорові особливості об’єкта, підлягають модифікації для зміни зовнішності. 3D- модель є багатофакторним джерелом інформації про пацієнта, дозволяє істотно знизити необхідний обсяг взаємодії з користувачем порівняно з існуючими методами. У роботі запропоновано використовувати тривимірне моделювання для визначення масо-вагових характеристик людини по її антропометричних параметрах. Для цього використовують 3D-сканери (боді-сканери для оцифрування тіла), що дає можливість створювати в 3D просторі модель тіла людини на повний зріст, а також окремих частин тіла. Використання тривимірного моделювання для діагностики має такі переваги: висока оперативність проведення обстеження; висока достовірність діагностики; можливість проведення обстежень пацієнтів у різних позиціях; висока точність вимірювання, можливість архівування, безконтактний метод вимірювання. Проведено аналіз предметної галузі. Наведено формули для розрахунку індексу маси тіла, об'єму тіла, відсотку жиру в організмі, площі тіла, відсоток підшкірного жиру в тілі на основі вимірянь параметрів по тривимірній моделі. Запропоновано метод визначення площі тіла з використанням полігональної моделі людини шляхом знаходження суми площ складових трикутників. Запропоновано метод визначення об’єму тіла з використанням тривимірної моделі людини шляхом виконання зрізів горизонтальними площинами. В результаті отримують сегмент тіла. Отриманий верхній зріз триангулюють з метою заміщення сегменту трикутними призмами. Для цього використовують вертикальні площини, які перпендикулярні до основи сегменту. У подальшому знаходять об’єми складових трикутних призм, якими заміщують сегменти. Сума їх об’ємів визначає об’єм сегменту. Для знаходження об’єму тіла людини підсумовують об’єми складових сегментів з урахуванням масштабу. Проведені дослідження можуть бути використанні в медичній практиці.

Urban Scene LOD Vectorized Modeling From Photogrammetry Meshes.

Urban scene modeling is a challenging task for the photogrammetry and computer vision community due to its large scale, structural complexity, and topological delicacy. This paper presents an efficient multistep modeling framework for large-scale urban scenes from aerial images. It takes aerial images and a textured 3D mesh model generated by an image-based modeling system as the input and outputs compact polygon models with semantics at different levels of detail (LODs). Based on the key observation that urban buildings usually have piecewise planar rooftops and vertical walls, we propose a segment-based modeling method, which consists of three major stages: scene segmentation, roof contour extraction, and building modeling. By combining the deep neural network predictions with geometric constraints of the 3D mesh, the scene is first segmented into three classes. Then, for each building mesh, the 2D line segments are detected and used to slice the ground into polygon cells, followed by assigning each cell a roof plane via a MRF optimization. Finally, the LOD model is obtained by extruding cells to their corresponding planes. Compared with direct modeling in 3D space, we transform the mesh into a uniform 2D image grid representation and most of the modeling work is performed in 2D space, which has the advantages of low computational complexity and high robustness. In addition, our method doesn't require any global prior, such as the Manhattan or Atlanta world assumption, making it flexible to model scenes with different characteristics and complexity. Experiments on both single buildings and large-scale urban scenes demonstrate that by combining 2D photometric with 3D geometric information, the proposed algorithm is robust and efficient in urban scene LOD vectorized modeling compared with the state-of-the-art approaches.

Method of the key point correspondence search in the sequences of digital images

The approach to definition of positions of points of view which provide the set visibility coefficient is developed. The proposed approach was tested on a polygonal terrain model. The result of the work is the creation of computational tool for research of the survey ability of sets of points in three-dimensional space relative to given polygonal geometric models. The proposed method is implemented in the form of a software tool that allows you to find the minimum required set of points given on a regular grid, which covers an open surface polygonal model and to visualize the results of research.. Figs.: 3. Refs.: 13.Keywords: point of view; coefficient of visibility; set of points; regular grid; polygonal terrain model

3D modeling in the studies of the portable art geometrical images of the Upper Paleolithic and Mesolithic of Eastern Europe

One of the plots of the portable art forms of Eastern Europe is abstract, geometric, symbolic images that cannot be deciphered directly. Most of the currently known such geometric images from the archaeological sites of the Upper Paleolithic and Mesolithic of Eastern Europe were applied to finished bone products — tools, weapons, household and non-utilitarian items, as well as bones of various animals without traces of processing using various cutting techniques. The bone is well preserved in the cultural layers of the sites of the late Pleistocene — early Holocene of the Russian Plain, which makes objects from this material an important source for the study of geometric images. However, despite the richness of the source base, the problem of classification and systematization of geometric images in the art of small forms remains poorly developed. The purpose of the article is to consider the issues of practical application of three-dimensional 3D modeling in the study of art objects of small forms of the Upper Paleolithic and Mesolithic. The authors describe the practice of photographing such objects and the peculiarities of the lighting schemes and camera positioning, developed taking into account the specifics of the geometry and material of the documented objects. The minimal technical requirements for the resolution of the models have been determined, which provide the possibility of using visualization algorithms to study fine engravings on bone and stone. The practical application of mathematical visualization algorithms both directly on polygonal models and on height maps built on their basis is described. A method for visualizing and systematizing research results and providing remote access to them using modern web technologies is proposed.