Movement Of Control Points Research Articles

Adaptive grid deformation method for CFD application to hull optimization

This work introduces a new grid deformation method for an efficient CFD-based optimization of ship hull forms. The method uses a two-level point transformation technique to manipulate grid points with a small number of design points. At the first level, generic B-spline is employed to transfer grid points based on movements of control points sampled inside a control box, ensuring accuracy and smoothness of surface modification. At the second level, Radial Basis Function with Wendland’s C2 continuity is adopted to interpolate movements of control points based on relatively few design points. It is shown to be effective in preserving good mesh quality and efficiency. The method is applied to the deformation of hull surfaces for ship models KVLCC2 and KCS, and to investigate the effects of bulbous bow on calm-water resistance with fixed Lpp. A regression model is proposed for ship length, location of buoyancy, wet surface area, and displacement. Numerical results show that the present method is well-suited for CFD-based hull form optimization with better efficiency.

Improvement of FFD parametric approach in the application of a lifting body

AbstractFFD (free-form deformation method) is one of the most commonly used parameterisation methods at present. It places the parameterised objects inside the control volume through coordinate system transformation, and controls the control volume through control points, thus realising the deformation control of its internal objects. Firstly, this paper systematically analyses and compares the characteristics and technical requirements of Bernstein, B-spline and NURBS (non-uniform rational b-splines) basic functions that can be adopted by FFD, and uses the minimum number of control points required to achieve the specified control effect threshold to express the control capability. Aiming at the problem of discontinuity at the right end in the actual calculation of B-spline basis function, a method of adding a small epsilon is proposed to solve it. Then, three basic functions are applied to the FFD parameterisation method, respectively, and the differences are compared from two aspects of the accurate expression of the model and the ability of deformation control. It is found that the BFFD (b-spline free-form deformation) approach owns better comprehensive performance when the control points are distributed correctly. In this paper, the BFFD method is improved, and a p-BFFD (reverse solution points based BFFD) method based on inverse solution is proposed to realise the free distribution of control points under the specified topology. Further, for the lifting body configuration, the control points of the p-BFFD method are brought closer to the airframe forming the EDGE-p-BFFD (edge constraints based p-BFFD) method. For the case in this paper, the proposed EDGE-p-BFFD method not only has fairly high parameterisation accuracy, but also reduces the expression error from 1.01E-3 to 1.25E-4, which is nearly ten times. It can also achieve effective lifting body guideline constraints, and has the ability of local deformation adapting to the configuration characteristics. In terms of the proportion of effective control points, the EDGE-p-BFFD method increases the proportion of effective control points from 36.7% to 50%, and the more control points, the more obvious the proportion increase effect. The new method also has better effect on the continuity of geometric deformation. At the same time, this paper introduces the independent deformation method of the upper and lower surfaces based on the double control body frames, which effectively avoids the deformation coupling problem of the simultaneous change of the upper and lower surfaces caused by the movement of control points in the traditional single control framework.

Method for 3D Images Transformation and Streaming over Low Bandwidth Communication Networks

The article describes an approach to streaming 3D human images over communication networks allowing to significantly reduce network bandwidth requirements by transmitting not the image itself, but data on the movement of control points. The subject of the study is 3D moving images of a person data on the movement of their control points. The main results of the work: a system of three applications that allows to record data about object movements, convert it into coordinates of key points, transfer it over communication networks and play it in the form of movements of a 3D object in an augmented reality application. The practical significance of the work lies in the possibility of using the developed applications for streaming moving 3D objects over low bandwidth networks. The application can be used in remote education or other areas.

Določitev geodetskega datuma mreže na plazu Urbas

This article describes the geodetic network of the Urbas landslide. It is the largest landslide in the Koroška Bela region, which, if triggered, can endanger human lives and damage infrastructure. In order to monitor the landslide, a geodetic network was established in the area of the Urbas landslide, on the basis of which the movements of control points can be calculated. After various analyses, only two small areas near the Urbas landslide proved to be stable, so we established four reference points there. In this research we defined the geodetic datum of the geodetic network of the Urbas landslide. The geodetic datum was defined on the basis of four measurement epochs processed with our own software.

NURBS plasticity: Yield surface evolution and implicit stress integration for isotropic hardening

This paper extends the non-uniform rational basis spline (NURBS) plasticity framework of Coombs et al. (2016) to include isotropic hardening of the yield surfaces. The approach allows any smooth isotropic yield envelope to be represented by a NURBS surface. The key extension provided by this paper is that the yield surface can expand or contract through the movement of control points linked to the level of inelastic straining experienced by the material. The model is integrated using a fully implicit backward Euler algorithm that constrains the return path to the yield surface and allows the derivation of the algorithmic consistent tangent to ensure optimum convergence of the global equilibrium equations. This provides a powerful framework for elasto-plastic constitutive models where, unlike the majority of models presented in the literature, the underlying numerical algorithm (and implemented code) remains unchanged for different yield surfaces. The performance of the algorithm is demonstrated, and validated, using both material point and boundary values simulations including plane stress, plane strain and three-dimensional examples for different yield criteria.

Monumentations of control points for the measurement of soil vertical movements and their interactions with ground water contents

Historically, one of the techniques used in the study of vertical movements of soil is that of high precision spirit levelling. Nowadays, this technique is often accomplished by satellite interferometric synthetic aperture radar (SAR) analysis that requires a calibration phase, i.e. through the connection to a spirit levelling network or by means of a long time series acquired by global navigation satellite systems permanent stations in order to transform relative velocities derived by SAR in absolute terms. An important aspect of this process consists of the materialization of the object used as a control point, while its selection may depend on the geological context. Typically, due to the inevitably high cost of installation, very accurate monumentation is reserved only for a limited density of points on the territory; therefore, a type of negative correlation exists, in terms of reliability in the monumentation of the control points, with respect to their density in a real distribution within a specific monitoring technique. For example, in levelling networks, a density of one benchmark every 700–1000 m of line is often desired in order to reach a compromise among costs, practical operative requirements and precision. Levelling benchmarks are usually fixed on existing structures (i.e. buildings or concrete structures). This aspect is even more evident in the case of SAR interferometric analysis, where the persistent scatterers (PS) are identified based on the coherence in the radar response. Therefore, the PS display movements are measured by a variety of different structures, characterized by foundations fixed at different depths.Starting from repeated levelling measurements, we verified the order of magnitude of movements of control points characterized by shallow foundations in cohesive soils. In practice, we observed their behaviour in relation to the depth of the foundation under simple and very common conditions, such as the presence of periods of drought or rainfall. The results indicate movements in the order of 3–7 mm in the first metre of depth that occurred in a week during the transition between the period of summer drought and the first rains. The magnitude of the total uplift observed between the end of the summer drought and the beginning of successive springtime (30/08/2012–18/04/2013) exceeded 10 cm of movement in very shallow layers of the soil surface for the same test field.

EXPERIMENTAL TEST ON CONTROL POINTS MATERIALIZATION FOR THE STUDY OF VERTICAL MOVEMENTS OF SOIL AND ITS INTERACTIONS WITH GROUND WATER CONTENTS

Abstract. In the study of soil vertical movements, one of the techniques most commonly used is the spirit levelling, now flanked by satellite SAR interferometry and by the analysis of time series acquired through permanent GNSS stations. The reliability of control points monuments varies depending both on the geological context and on the structure being representative of the investigated phenomenon. Often due to the high number of desired points or to the need of maintaining a specific areal distribution, they are fixed on existing structures (as in the common case of spirit levelling networks). This aspect is even more evident in the case of SAR interferometric analysis, where the permanent scatterers are identified on the basis of consistency in the radar response, but the points display movements measured by structures with different foundations at different depths. Starting from repeated precision levelling measurements, we verified which is the order of magnitude of movements of control points characterized by shallow foundations in cohesive soils, observing their behaviours at different depths, under simple and very common conditions such as the presence of periods of drought or rainfall. The results point-out movements in the order of 3–7 mm in the first meter of depth occurred in a week, during the transition between the period of summer drought and the first rains.

2P1-Q12 CG 顔を実機で作るための複合線路を利用する曲面追従機構を備えた口表情デバイスの実現(アミューズメント・エンタティナーロボット)

We developed a robot face that can mechanically create facial expressions that actualizes 3D computer graphic morphing techniques, especially around the mouth. Using the mechanism we expect robots to have a wider range of expressions in human-robot communication, not just emotion theory based expressions but expressions that are designed and created. The facial expression mechanism uses multiple control points that moves and traces the surface of the robot's face using combination of trajectories. The movements of control points used here are similar to the transferring vertices that changes expressions of graphical models seen in 3D-CG, therefore actualizes computer graphics. At the end of the paper we evaluate the actualization by overlapping the computer graphic expression images and the actual robot expressions and see the visual closeness of the two expressions.

Artifact analysis on triangular box-splines and subdivision surfaces defined by triangular polyhedra

Surface artifacts are features in a surface which cannot be avoided by movement of control points. They are present in B-splines, box splines and subdivision surfaces. We showed how the subdivision process can be used as a tool to analyse artifacts in surfaces defined by quadrilateral polyhedra ( Sabin et al., 2005; Augsdörfer et al., 2011). In this paper we are utilising the subdivision process to develop a generic expression which can be employed to determine the magnitude of artifacts in surfaces defined by any regular triangular polyhedra. We demonstrate the method by analysing box-splines and regular regions of subdivision surfaces based on triangular meshes: Loop subdivision, Butterfly subdivision and a novel interpolating scheme with two smoothing stages. We compare our results for surfaces defined by triangular polyhedra to those for surfaces defined by quadrilateral polyhedra.

Artifact analysis on B-splines, box-splines and other surfaces defined by quadrilateral polyhedra

When using NURBS or subdivision surfaces as a design tool in engineering applications, designers face certain challenges. One of these is the presence of artifacts. An artifact is a feature of the surface that cannot be avoided by movement of control points by the designer. This implies that the surface contains spatial frequencies greater than one cycle per two control points. These are seen as ripples in the surface and are found in NURBS and subdivision surfaces and potentially in all surfaces specified in terms of polyhedrons of control points. Ideally, this difference between designer intent and what emerges as a surface should be eliminated. The first step to achieving this is by understanding and quantifying the artifact observed in the surface. We present methods for analysing the magnitude of artifacts in a surface defined by a quadrilateral control mesh. We use the subdivision process as a tool for analysis. Our results provide a measure of surface artifacts with respect to initial control point sampling for all B-Splines, quadrilateral box-spline surfaces and regular regions of subdivision surfaces. We use four subdivision schemes as working examples: the three box-spline subdivision schemes, Catmull–Clark (cubic B-spline), 4-3, 4-8; and Kobbeltʼs interpolating scheme.

Patches: character skinning with local deformation layer

AbstractWe present a layered geometric approach to the skinning of character animation. On top of a global shape deformation, B‐spline surface patches are attached to various body parts for local control. The patches are directly manipulated so as to generate example local shapes at some important poses. During character animation, the B‐spline control points move continuously by kinematically interpolating a set of example patches, and at the same time they can also move dynamically by elastic simulation. The movement of control points changes the shape of a local patch, and consequently skin vertices move according to the patch deformation, finally generating the desired local deformation. We demonstrate the effectiveness of our approach by generating natural local details at various poses including muscular effects and elastic deformation. Moreover, dealing with only a small number of control points, the proposed method is very efficient, while generating hundreds to thousands frames per second. Copyright © 2009 John Wiley & Sons, Ltd.

Improved precision levelling for deriving significant vertical movements of the earth's crust

The accuracy and reliability of determinations of recent vertical crustal movements are determined by the quality of precise elevation measurements, by the knowledge of the effects of errors that are unavoidable in the measuring set-ups and their propagation, and by the methods of error analysis and of evaluation of measurements. The accuracy of precise levelling techniques is essentially defined by • -the performance of the equipment, • -effects such as the sinking in of levelling rods, rod graduation errors and asymmetric refraction which cannot be completely avoided in measurement set-ups, • -movements of control points during the period of measurement. Measures for increasing the accuracy of levellings for the derivation of crustal movements are • -to garantee the reliability of data acquisition using automatic data recording, • -metrological determination of external influences on the measuring system, such as sinking in of levelling rods and asymmetric refraction, • -further acceleration of the measuring process.