3D Curves Research Articles

Tree Trunk Curvature Extraction Based on Terrestrial Laser Scanning Point Clouds

The degree of tree curvature exerts a significant influence on the utilization of forestry resources. This study proposes an enhanced quantitative structural modeling (QSM) method, founded upon terrestrial laser scanning (TLS) point cloud data, for the precise extraction of 3D curvature characteristics of tree trunks. The conventional approach operates under the assumption that the tree trunk constitutes an upright rotating body, thereby disregarding the tree trunk’s true curvature morphology. The proposed method is founded on the classical QSM algorithm and introduces two zoom factors that can dynamically adjust the fitting parameters. This improvement leads to enhanced accuracy in the representation of tree trunk curvature and reduced computational complexity. The study utilized 146 sample trees from 13 plots in Jixi, Anhui Province, which were collected and pre-processed by TLS. The study combines point cloud segmentation, manual labeling of actual curvature and dual-factor experiments, and uses quadratic polynomials and simulated annealing algorithms to determine the optimal model factors. The validation results demonstrate that the enhanced method exhibits a greater degree of concordance between the predicted and actual curvature values within the validation set. In the regression equation, the coefficient of the two-factor method for fitting a straight line is 0.95, which is substantially higher than the 0.75 of the one-factor method. Furthermore, the two-factor model has an R2 of 0.21, indicating that the two-factor optimization method generates a significantly smaller error compared to the one-factor model (with an R2 of 0.12). In addition, this study discusses the possible reasons for the error in the results, as well as the shortcomings and outlook. The experimental results demonstrate the augmented method’s capacity to accurately reconstruct the 3D curvature of tree trunks in most cases. This study provides an efficient and accurate method for conducting fine-grained forest resource measurements and tree bending studies.

An Innovative Stepwise C-Means Clustering Approach for Classification of Adolescent Idiopathic Scoliosis.

Existing 3D classification systems for scoliosis primarily guide surgical treatment, with limited application in conservative management. This study aims to establish a preliminary 3D classification system for moderate adolescent idiopathic scoliosis patients in China, providing a theoretical foundation for the standardization and automation of conservative treatment plans. Data from 404 adolescent idiopathic scoliosis patients who did not undergo surgery were retrospectively collected from 2022 to 2025. EOS imaging technology was used to perform 3D reconstruction for each patient. The parameters included the 3D centroid coordinates of the vertebrae and vertebral angular displacement. A total of 102 features were extracted per model, and dimensionality reduction yielded 30 final features by the Stacked Autoencoder method. Fuzzy C-means clustering with two classification approaches is used: direct clustering and iterative clustering. Iterative clustering was performed based on coronal plane parameters for initial classification, followed by further clustering. Direct classification involved immediate clustering without further subdivision. Clustering identified 8 distinct 2D curve types, which were further subdivided into 13 3D subtypes. A comparison of the 13 clusters from direct classification with those obtained from iterative clustering was made using Euclidean and Mahalanobis distances between cluster centers and clinical data. The difference in similarity was higher for direct classification, indicating greater variability. EOS imaging technology combined with Fuzzy C-Means iterative clustering enables a preliminary 3D classification of AIS by capturing more detailed and individualized morphological features. Compared to direct clustering, the iterative method not only improves geometric interpretability but also enhances classification accuracy by better identifying subtle variations in spinal curvature. It further improves specificity, particularly in distinguishing sagittal and axial plane deformities, which are often overlooked in 2D systems. This enhanced resolution provides a stronger basis for developing personalized conservative treatment plans, such as brace design and rehabilitation strategy. Although the proposed method shows promise, further clinical validation is needed to confirm its effectiveness in guiding conservative treatment decisions.

3DStrainOrientationCalculator: a 3D diffraction data analysis tool for single-crystal substructure information extraction

Neutron diffraction is a crucial non-destructive technique for obtaining statistical information on the bulk properties of engineering materials. The program 3DStrainOrientationCalculator (3DSOC) is an innovative analytical tool designed to extract substructure information, including lattice strain and subgrain orientation, from single crystals (SCs) using monochromatic neutron diffractometer data. By separating subgrain diffraction via rocking curve analysis and employing 2D curve fitting on original diffraction data, 3DSOC accurately determines the diffraction intensity of individual subgrains while minimizing the impact of scanning step size on the final fitting results. It reduces the standard deviation of the fitting result's statistical error from the order of 10−3 to around 10−5. Additionally, 3DSOC extends its capabilities to the analysis of dual-phase SCs, where the lattice parameters of both phases are maintained with an accuracy of 10−4 nm, comparable to conventional methods. This study applies 3DSOC to SiC SCs and Ni-based SC superalloys, measured using two different diffractometers, and discusses the resulting improvements.

An adaptive hexahedral mesh generation method for industrial CT images

This article presents a method for the direct generation of an adaptive hexahedral mesh from industrial computed tomography (CT) images. First, the two-dimensional (2D) Shi-Tomasi algorithm is extended to the three-dimensional (3D) space to extract the 3D curvature feature points of the workpiece, and the initial non-uniform core mesh is obtained by adaptive partitioning of the octree based on the feature points information. Subsequently, to address the issue of hanging nodes within the initial non-uniform core mesh, a search template for hanging node transition chain is devised to locate these nodes, and the template method is employed to eliminate the hanging nodes from the transition chain. Then, to enhance the quality of the boundary mesh, the vector projection method is introduced for surface fitting of the core mesh, and the Laplace algorithm of vector projection optimization is combined to optimize the boundary mesh. Finally, the adaptive hexahedral mesh is generated directly from the industrial CT images obtained through actual scanning. Quality evaluation results demonstrate that the scaled Jacobian of the hexahedral mesh exceeds 0, which confirms the correctness and effectiveness of the proposed method.

IMPLICIT CURVES AND SURFACES MODELING WITH PSEUDOGAUSSIAN INTERPOLATION

Context. With the contemporary development of topological optimization, and parametric and AI-guided design, the problem of implicit surface representation became prominent in additive manufacturing. Although more and more software packages use implicit modeling for design, there is no common standard way of writing, storing, or passing a set of implicit surfaces or curves over the network. The object of the study is one of the possible ways of such representation, specifically: modeling implicit curves and surfaces using pseudo-Gaussian interpolation.Objective. The goal of the work is the development of a modeling method that improved the accuracy of the implicit object representation wothout significant increase in memory used or processing time spent.Method. One of the conventional ways to model an implicit surface would be to represent its signed distance function (SDF) with its values defined on a regular grid. Then a continuous SDF could be obtained from the grid values by means of interpolation.What we propose instead is to store not SDF values but the coefficients of a pseudo-Gaussian interpolating function in the grid, which would enable picking the exact interpolation points before the SDF model is written. In this way we achieve better accuracy in the regions we’re interested the most in with no additional memory overhead.Results. The developed method was implemented in software for curves in 2D and validated against several primitive implicit curves of different nanture: circles, sqaures, rectangles with different parameters of the model. The method has shown improved accuaracy in general, but there were several classes of corner cases found for which it deserves further development.Conclusions. Pseudo-Gaussian interpolation defined as a sum of radial basis functions on a regular grid with points of interpolation defined in the proximity of the grid points generally allows to model an implicit surface more accurately than a voxel model interpolation does. The memory intake or computational toll isn’t much different in these two approaches. However, the interpolating points selection strategy and the choice of the best modeling parameters for each particular modeling problem remain an open quesition.

A novel method for analyzing foot motion during circumduction using an electromagnetic tracking system.

Circumduction of the hindfoot does not occur primarily in one of the traditional anatomic planes and can be difficult to describe precisely. The purpose of this study was to measure foot bone motion quickly and objectively to subsequently characterize differences among feet of varying shapes. As such, we have developed a quantitative characterization of foot bone motion during circumduction using electromagnetic tracking sensors. Five of these sensors were attached to the foot on specific bony landmarks, and one was attached to a footplate. The lower leg was held by padded clamps in a custom non-ferrous jig, and the foot was moved through a full range of circumduction. To describe the motion of the bones of the foot during circumduction, the sensor positions were fitted to 2D ellipses and 3D curves. A repeatability study on multiple feet (n = 7) demonstrated that multiple raters (n = 3) introduced more error than a single rater; therefore, a single rater was used for all subsequent data collection. Results from five neutrally aligned subjects demonstrated that bone motion was quantifiable by fitted ellipse parameters. Additional modeling with a paraboloid surface described the motion with improved accuracy. A further reduction in error was obtained using a 3D eighth-order Fourier series expansion fit. This method holds promise as a means for characterizing differences in foot bone motion among foot types during a clinical exam.

Aero-propulsive coupling performance and design of distributed propulsion wing

Aero-propulsive coupling performance and design of distributed propulsion wing

Quantitative Analysis of 3D Anatomy to Inform Planning of Ductal Arteriosus Stenting.

Ductus arteriosus stenting (DAS) is used to palliate infants with ductal-dependent pulmonary blood flow (DD-PBF), however patent ductus arteriosus (PDA) anatomy can be complex and heterogenous. We developed custom, open-source software to model and quantify PDA anatomy. We retrospectively identified 33 neonates with DD-PBF with a CTA before DAS. A novel custom workflow was implemented in 3D Slicer and SlicerHeart to semi-automatically extract centerlines of the course of the PDA and surrounding vessels. 3D ductal length, diameter, curvature and tortuosity were automatically calculated (3D automatic) and compared to manually adjusted 3D measurements (3D semi-automatic), and manual measurements of PDA dimensions in 2D projectional angiograms before and after stent angioplasty. Ductal anatomy was successfully modeled and quantified in all subjects. 3D automatic and semi-automatic measurements of straight-line aortic to pulmonary artery length were not significantly different than 2D measurements. Semi-automatic 3D measurements were similar to 2D measurements of the total length. Minimum and maximum ductal diameters were not significantly different by 3D automatic and 2D measurements, however semi-automatic 3D diameters were significantly larger. Inter-reader reliability of ductal length and diameter was higher with manual adjustment of 3D centerlines compared to standard measurement of 2D angiograms. These differences were consistent across PGE doses between CTA and DAS. Automatic PDA modeling is feasible and efficient, enabling reproducible quantification of ductal anatomy for procedural planning of DAS in patients with DD-PBF. Further development is needed as well as investigation of whether 3D modeling-derived measurements influence procedural duration or outcome.

HoldTabSketch: Enhancing Bimanual Interaction Realism in VR Sketching Using a Graphics Tablet as a Seamless Touch-Sensitive Physical Proxy

Current Virtual Reality (VR) sketching systems lack natural bimanual interactions for drawing curves on 3D models. This article introduces HoldTabSketch, a VR sketching system that uses a tracked graphics tablet as a touch-sensitive physical proxy to enable realistic bimanual interactions for 3D curve drawing. The system features a Reoriented Bounding Boxes (ROBB) haptic redirection technique that automatically aligns virtual pen and hand movements with various virtual objects while maintaining tactile feedback. The system supports two additional bimanual interaction modes: 1) bare-hand object manipulation with pen-based sketching using visual feedback, and 2) tablet-assisted tangible interactions combining grasp support and surface drawing. A 12-user comparative study showed the tablet-based physical proxy significantly improved the realism of 3D object manipulation and surface drawing, yielding higher user preference and usability compared to vision-only or basic tangible approaches. The system demonstrates how hybrid physical-digital proxies can enhance 3D creative workflows in VR.

High accuracy calibration method for 3D curve reconstruction based on a twisted multicore fiber.

A high accuracy calibration method for three-dimensional (3D) curve reconstruction based on a twisted multicore fiber (MCF) is proposed and experimentally investigated. The core spacing, core azimuth, and twist bias of the twisted MCF are decoupled and calibrated according to the amplitude, phase, and period information derived from the strain curves. A 3D curve reconstruction experimental system based on the twisted MCF and optical frequency domain reflectometry (OFDR) is established, and the curve reconstruction performance is evaluated before and after calibration. The results show that, with a reconstruction length of 25 cm, the average tip position error is reduced from 28.12 to 2.50 mm.

Agomelatine Transdermal System Product Cycle: Development, Material/Process Screening, Optimization, Characterization, Delivery Mechanics and Irritation study on Rat.

Agomelatine (AGT) is used for the treatment of major depressive disorder in adults. Agomelatine is highly susceptible to first-pass metabolism, and it has less than 5% oral bioavailability. Therapy for major depressive disorder extends for a long period and every time, additional caregivers are required to remind and manage the timely dosing of oral medicine to patients. In such cases, once a week, administration of agomelatine via transdermal patch dosage form provides major patient benefits and lowers overall therapy costs. An agomelatine transdermal patch was prepared using the solvent evaporation method using the LTE-S Werner Mathis AG coater and dryer. A patch was prepared using silicon adhesive after screening different pressure-sensitive adhesives like acrylate, polyisobutylene, and silicon. To make a crystal-free patch, the concentration of povidone k-29/32 was optimized in preliminary trials. To deliver the drug over a 7-day period, propylene glycol monolaurate (PGML) was identified from different penetration enhancers. Three factors optimization was carried out, like the concentration of povidone k-29/32, the concentration of PGML, and the mixing time of the blend using the Box Behnken design. 3D surface response curves and contour plots were derived using Design Expert and Minitab software. From overlay plots, design spaces were identified. The optimized AGT patch has good adhesion properties along with a desirable flux of 4.63 μg/cm2/h on human cadaver skin along with a lower residual drug. There was no impact of heat flux studies on normal conditions, hence justifying the in-use condition of the patient population during hot showers, baths, and saunas. AGT Patch was also non-irritating in skin irritation studies performed on Wistar albino rats. It was concluded that agomelatine transdermal patches can be manufactured using silicon adhesive, povidone k-29/32, and propylene glycol monolaurate for the treatment of major depressive disorder and will be the most convenient and cost-effective therapy for the patient.

Exploring the Factors Affecting the Injury Severity of Crashes on Mountainous Freeways with High Proportions of Heavy Vehicles Considering Their Heterogeneous and Interactive Effects

Freeway transportation safety issues have attracted public concern in China for decades. This study aims to identify the factors influencing the injury severity of freeway crashes and to quantify their effects on the likelihood of various crash severity levels, with consideration of heterogeneity and interactions. The empirical analysis is based on three years of crash data from two mountainous freeways in Guangdong, China, covering the years of 2021 to 2023. A random parameters logit model with interaction terms is developed for the analysis. Goodness-of-fit indicators reveal that accommodating the interactive effects can significantly improve model fit performance. The estimation results of the parameters and marginal effects indicate that the factors related to vehicle type, time of day, crash season and cause, 3D curvature, and traffic volume have significant effects on crash severity. Notably, interactive effects are revealed between spring and evening, autumn and fixed objects, and non-local vehicles and improper driving. According to the findings, some countermeasures on safety education, traffic management, and freeway design are provided for preventing freeway crash injury, which is helpful for the development of sustainable transportation systems.

Quantifying radiotherapy beam quality: an analysis using gamma passing rates

Purpose. PDD and profile curves play a crucial role in analyzing the beam quality and energy stability of accelerators. The aim of this study was to assess the efficacy of GPR in machine QA and compare it with traditional methods for analyzing dose outputs.Methods. GPRs were employed to assess the quality of radiation beams by comparing 1D and 2D Profile metrics and PDD data against commissioning data. The data used were obtained from the ASCII data files derived from the water tank. GPRs were calculated for all plots with a lower percentage dose cutoff of 10%. The local GPRs and dose influence for the 2D PDD metrics and dose influence were calculated for an open field 10×10 cm2photon beam at SSD = 100 cm. In both 1D and 2D GPRs analyses, criterion of 1%/1 mm was adopted, as this approach allows for the capture of more subtle variations in the data. To substantiate the viability of the study, a comparative analysis was conducted by comparing the outcomes of the gamma analysis with those derived from traditional methods, such as manual machine quality assurance checks.Results. GPRs demonstrated a superior capability for comprehensive data analysis compared to traditional methods. For the 1D curves, the passing rates (γ≤ 1) are 96.19%, 100%, and 93.46%, respectively. With respect to the 2D dose influence, the PDD image passing rate was 99.57%, and significant dose differences were observed at the four corners of the open field, indicating areas that require further investigation.Conclusions. Compared to traditional methods, GPRs are more sensitive to subtle changes in the data, providing valuable insights into the accelerator beam status.

Inverse Design of Three-Dimensional Variable Curvature Pneumatic Soft Actuators

Abstract The inverse design of soft actuators refers to a design methodology that derives the actuator's geometric and material parameters based on the desired target shape. This approach offers an efficient solution for developing soft actuators with complex geometries, enabling the precise matching of intricate deformation targets. Furthermore, it facilitates personalized customization and design optimization for complex application scenarios. In this article, we present a novel inverse design method for three-dimensional (3D) variable curvature pneumatic soft actuators and incorporate buckling deformation to improve shape matching. By analyzing variable cross-sectional actuators, we demonstrate that cross-sectional curvature is determined solely by its shape, enabling specific curvatures to be achieved by adjusting the cross-sectional geometry. To process input 3D point coordinates and calculate curve curvatures, we introduce cubic spline interpolation and the three-point circle method. Additionally, a minimum discretization method is proposed to identify the helical axis for helical curves. Finally, based on the actuator's deformation model, we develop an inverse design program to achieve the desired actuator shape. Finite element simulations and experimental validation confirm the effectiveness of this approach, demonstrating that the fabricated actuators can precisely match complex 3D variable curvature shapes. The proposed approach has broad potential applications in situations that require specific, repetitive use, such as specific object grasping and customized medical rehabilitation devices.

Warpage mitigation through infill sectioning in fused filament fabrication

This study addresses the warpage issues in Fused Filament Fabrication (FFF) processes by strategically dividing infills to redistribute shrinkage forces, thereby mitigating warpage. The efficacy of these adjustments is evaluated quantitatively through 3D scanning and curvature assessment, coupled with an experimental design approach to optimize sectioning criteria. This sectioning method is particularly beneficial for translational studies where FFF is used to fabricate parts. Our case study focuses on two sample types—round cap parts and long wrench parts—to exemplify challenges related to their geometric characteristics when printed with desktop FFF 3D printers. Results show significant reductions in mean and maximum curvature and height deviations, indicating improvements in print quality and geometric fidelity. However, increased printing times and potential compromises in mechanical strength are noted as drawbacks. These findings enhance the understanding of the interplay between print parameters, part geometry, and designing for additive manufacturing, underscoring the need for further research to balance efficiency and structural integrity in additive manufacturing applications. Future research should explore the benefits of this sectioning strategy in other additive manufacturing processes beyond FFF.

A Novel Depth Information‐Guided Multi‐View 3D Curve Reconstruction Method

ABSTRACTCurve features, being more versatile than line segment features, are better suited for scene abstraction. However, obtaining three‐dimensional (3D) curves with high scene coverage from multi‐view images is a challenging task. In this study, we proposed a 3D curve reconstruction method guided by depth information. By utilizing depth information to narrow the search range of candidate two‐dimensional (2D) curve matches, we mitigate the interference of non‐corresponding curves on 2D curve matching, thereby improving the accuracy and recall rate of 2D curve matching. This results in reliable 3D curves with high scene coverage. For a curve on the reference image, we use depth information to project it onto the search image and design a purely geometric similarity measurement based on the projected curve to obtain 2D curve correspondences. Then, we generate 3D hypotheses based on the two‐view matching results and design a robust geometric similarity measurement to obtain concise and reliable 3D curves from the redundant 3D hypotheses. Finally, we provide a curve‐based bundle adjustment to achieve 3D curves with higher positional accuracy. We tested our method on five open‐source datasets, demonstrating its effectiveness in generating 3D curves with high scene coverage, particularly in curved structure areas. Our method reconstructs 3.69 times more 3D lines on average than the best comparison method on five datasets, while also achieving higher positional accuracy.

Curvature Perception of Mesenchymal Cells on Mesoscale Topographies.

Cells can sense geometrical cues with sizes of several tens of micrometers in their vicinity. Recent in vitro studies show that cells can adapt their shape, align along specific directions, or regulate other cellular functions when grown on surfaces with curvatures larger than their size. Although possible mechanisms for such responses like the alignment along axial cues have been suggested, a detailed understanding of the involved cellular processes remains open. This work addresses this gap by systematically investigating mesenchymal cell and nucleus orientation responses using a low-cost model surface platform, the CurvChip. Using an array of cylindrically curved topographies with radii of curvatures ranging from tens to hundreds of micrometers, the contact guidance response of cells and nuclei is quantified in dependence on substratum curvature and manipulation of cytoskeletal components. Results suggest a desired perceived curvature for the investigated cells, and a very sensitive and robust curvature perception mechanism, as the effect of pharmacological manipulation of cytoskeletal components is relatively small. Furthermore, a comparison with previously published work strengthens the hypothesis of an involvement of the nucleus in the cell response to three-dimensional (3D) curvatures.

Quasi-conformal versus Hertz superposition: a comparison for two-dimensional contact

Hertz contact theory results in a relation between the normal contact force and the rigid indentation of the contact surfaces, the force is proportional to the indentation to the power of 3/2, and a semi-ellipsoidal traction distribution. It is a valid theory for non-conformal contact between smooth surfaces (curves in 2D) of elastic bodies. This force model can be derived by considering the Taylor polynomials of degree 2 at the contact point as approximations for the surfaces/curves. In the 2D case, it depends only on the curvature radii of the curves and is undefined when they are equal, the equality of radii violates the non-conformality.The Hertzian force is usually applied to the contact of solid particles as a model compensating for the small local deformations that occur in the contact region. We consider the 2D contact of a rigid convex particle with a rigid concavity enforcing the contact constraint with a barrier method, an approach that prevents overlapping of the bodies, resulting in a force that acts on the contact point. The geometries and the motion are specially designed to show the coalescence of two contact points into one. It illustrates two possible issues with convex-concave contact, the non-uniqueness of contact points and the conformality. We compare the results with a deformable finite element model for equivalent bodies and motion showing that there is a transition between a Hertzian and a non-Hertzian behavior. We conclude that a criterion for the conformality of curves must include the ever-present gap when a barrier method is used to enforce the constraint and the Hertzian force is not suitable for the coalescence of contact points.

Robust Approach Estimates Effective Length for Lateral Vibrations

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 217755, “To What Extent Can the Notion of an Effective Length Be Reliable To Assess the BHA Lateral Behavior?” by Mohamed Mahjoub, SPE, Ngoc-Ha Dao, SPE, and Khac-Long Nguyen, Helmerich & Payne, et al. The paper has not been peer reviewed. _ Many models in the industry use the notion of an effective length to make predictions about the bottomhole assembly (BHA). A criterion is chosen to cut the drillstring at a certain distance from the bit and use only that part for the computations. Though this method is computationally efficient, no consensus exists regarding what criteria should be chosen or a perfect method regarding the computation of that length. This study aims to compensate for the lack of in-depth analysis on this important subject. It shows the importance of understanding the strengths and limits of frequency-based models compared with more-complex time-domain modeling. Introduction The notion of effective length is widely used in the industry for various types of drillstring mechanical models, whether for directional purposes, survey corrections, or assessment of vibration behavior of the BHA. The drillstring is cut at a given distance from the bit, known as the effective length (see example in Fig. 1, where an approximately 45-m effective length is used for a computation to predict the BHA build and turn rates). Ideally, the choice of this length should reflect the independence of what is happening close to the bit from the rest of the drillstring. This approach has the obvious advantage of reducing computation time significantly but has the shortcoming of being insufficiently well defined. The study of BHA lateral dynamics is more challenging because of the transient nature of the external forces that act on the drillstring. In the complete paper, different computations are conducted on several types of BHAs in order to examine when the notion of an effective length is valid and reliable and to determine the primary factors that make it challenging to isolate BHA behavior from the rest of the drillstring. Models and Data The BHA model used in this paper was used in the literature to study the microtortuosity of well trajectories. The model combines bit directional characteristics with the BHA design, namely stabilizer placement, in order to predict BHA preferential or equilibrium 3D curvature. The effective length can affect the results of this type of computation by changing the distribution and intensity of contact forces, thereby changing the overall preferential curvature. For BHA dynamics, the simplest type of modeling is frequency-based and consists of predicting the natural frequencies of the system, which can be translated into critical or forbidden rotation speeds that should be avoided to prevent resonance. An intermediary approach, also based on frequency domain, is the use of forced vibration computations. Both frequency-based models are considered linear models and, thus, cannot account for the nonlinearities related to the contact and friction forces. The most complex type of dynamics study is carried out in time domain. In this case, the nonlinearities related to the contact and friction forces are taken into consideration in addition to other transient external excitations.

Automated extraction method of STM for 3D topology optimization based on moving morphable components

Automated extraction method of STM for 3D topology optimization based on moving morphable components