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Spatial and Spectral Hybrid image Classification for Rice Lodging Assessment through UAV imagery

REMOTE SENSING 2017年第6期9卷 1-19页

作者： Yang, Ming-Der Huang, Kai-Siang Kuo, Yi-Hsuan Tsai, Hui Ping Lin, Liang-Mao Natl Chung Hsing Univ Dept Civil Engn 145 Xingda Rd Taichung 402 Taiwan Chiayi Cty Govt Dept Agr 1 Sianghe 1st Rd Taibao City 61249 Chiayi Taiwan

Rice lodging identification relies on manual in situ assessment and often leads to a compensation dispute in agricultural disaster assessment. Therefore, this study proposes a comprehensive and efficient classification technique for agricultural lands that entails using unmanned aerial vehicle (UAV) imagery. In addition to spectral information, digital surface model (DSM) and texture information of the images was obtained through image-based modeling and texture analysis. Moreover, single feature probability (SFP) values were computed to evaluate the contribution of spectral and spatial hybrid image information to classification accuracy. The SFP results revealed that texture information was beneficial for the classification of rice and water, DSM information was valuable for lodging and tree classification, and the combination of texture and DSM information was helpful in distinguishing between artificial surface and bare land. Furthermore, a decision tree classification model incorporating SFP values yielded optimal results, with an accuracy of 96.17% and a Kappa value of 0.941, compared with that of a maximum likelihood classification model (90.76%). The rice lodging ratio in paddies at the study site was successfully identified, with three paddies being eligible for disaster relief. The study demonstrated that the proposed spatial and spectral hybrid image classification technology is a promising tool for rice lodging assessment.

关键词： rice lodging unmanned aerial vehicle (UAV) image-based modeling spectral and spatial hybrid image classification decision tree classification single feature probability

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Towards scalable, multi-view urban modeling using structure priors

Towards scalable, multi-view urban modeling using structure ...

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作者： Amine Bourki Universite Paris-Est

学位级别：博士

In this thesis, we address the problem of 3D reconstruction from a sequence of cali- brated street-level photographs with a simultaneous focus on scalability and the use of structure priors in Multi-View Stereo (MVS). While both aspects have been studied broadly, existing scalable MVS approaches do not handle well the ubiquitous structural regularities, yet simple, of man-made envi- ronments. On the other hand, structure-aware 3D reconstruction methods are slow and scale poorly with the size of the input sequences and/or may even require additional restrictive information. The goal of this thesis is to reconcile scalability and structure- awareness within common MVS grounds using soft, generic priors which encourage: (i) piecewise planarity, (ii) alignment of objects boundaries with image gradients and (iii) with vanishing directions (VDs), and (iv) objects co-planarity. To do so, we present the novel "Patchwork Stereo" framework which integrates photometric stereo from a handful of wide-baseline views and a sparse 3D point cloud combining robust 3D plane extraction and top-down image partitioning from a unified 2D-3D analysis in a princi- pled Markov Random Field energy minimization. We evaluate our contributions quantitatively and qualitatively on challenging urban datasets and illustrate results which are at least on par with state-of-the-art methods in terms of geometric structure, but achieved in several orders of magnitude faster paving the way for photo-realistic city-scale modeling.

关键词： Multi-View Stereo Structure Priors 3D Reconstruction image-based modeling Scalability Top-Down image Segmentation Urban modeling

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A noninvasive method for the determination of in vivo mitral valve leaflet strains

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2018年第12期34卷 e3142-e3142页

作者： Rego, Bruno V. Khalighi, Amir H. Drach, Andrew Lai, Eric K. Pouch, Alison M. Gorman, Robert C. Gorman, Joseph H., III Sacks, Michael S. Univ Texas Austin Dept Biomed Engn Inst Computat Engn & Sci Willerson Ctr Cardiovasc Modeling & Simulat Austin TX 78712 USA Univ Penn Perelman Sch Med Dept Surg Gorman Cardiovasc Res Grp Philadelphia PA 19104 USA

Assessment of mitral valve (MV) function is important in many diagnostic, prognostic, and surgical planning applications for treatment of MV disease. Yet, to date, there are no accepted noninvasive methods for determination of MV leaflet deformation, which is a critical metric of MV function. In this study, we present a novel, completely noninvasive computational method to estimate MV leaflet in-plane strains from clinical-quality real-time three-dimensional echocardiography (rt-3DE) images. The images were first segmented to produce meshed medial-surface leaflet geometries of the open and closed states. To establish material point correspondence between the two states, an image-based morphing pipeline was implemented within a finite element (FE) modeling framework in which MV closure was simulated by pressurizing the open-state geometry, and local corrective loads were applied to enforce the actual MV closed shape. This resulted in a complete map of local systolic leaflet membrane strains, obtained from the final FE mesh configuration. To validate the method, we utilized an extant in vitro database of fiducially labeled MVs, imaged in conditions mimicking both the healthy and diseased states. Our method estimated local anisotropic in vivo strains with less than 10% error and proved to be robust to changes in boundary conditions similar to those observed in ischemic MV disease. Next, we applied our methodology to ovine MVs imaged in vivo with rt-3DE and compared our results to previously published findings of in vivo MV strains in the same type of animal as measured using surgically sutured fiducial marker arrays. In regions encompassed by fiducial markers, we found no significant differences in circumferential(P = 0.240) or radial (P = 0.808) strain estimates between the marker-based measurements and our novel noninvasive method. This method can thus be used for model validation as well as for studies of MV disease and repair.

关键词： echocardiography in vivo strains image-based modeling mitral valve patient-specific model

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PAPARAZZI: Surface Editing by way of Multi-View image Processing

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ACM TRANSACTIONS ON GRAPHICS 2018年第6期37卷 221-221页

作者： Liu, Hsueh-Ti Derek Tao, Michael Jacobson, Alec Univ Toronto 40 St George St Toronto ON M5S 2E4 Canada

The image processing pipeline boasts a wide variety of complex filters and effects. Translating an individual effect to operate on 3D surface geometry inevitably results in a bespoke algorithm. Instead, we propose a general-purpose back-end optimization that allows users to edit an input 3D surface by simply selecting an off-the-shelf image processing filter. We achieve this by constructing a differentiable triangle mesh renderer, with which we can back propagate changes in the image domain to the 3D mesh vertex positions. The given image processing technique is applied to the entire shape via stochastic snapshots of the shape: hence, we call our method Paparazzi. We provide simple yet important design considerations to construct the Paparazzi renderer and optimization algorithms. The power of this rendering-based surface editing is demonstrated via the variety of image processing filters we apply. Each application uses an off-the-shelf implementation of an image processing method without requiring modification to the core Paparazzi algorithm.

关键词： geometry processing surface editing image-based modeling geometric deformation inverse graphics

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A patient-specific aortic valve model based on moving resistive immersed implicit surfaces

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BIOMECHANICS AND modeling IN MECHANOBIOLOGY 2017年第5期16卷 1779-1803页

作者： Fedele, Marco Faggiano, Elena Dede, Luca Quarteroni, Alfio Ecole Polytech Federale Lausanne CMCS MATHICSE SB Lausanne Switzerland Univ Pavia Dept Civil Engn & Architecture CompMech Grp Pavia Italy Politecn Milan Dipartimento Matemat MOX Milan Italy

In this paper, we propose a full computational framework to simulate the hemodynamics in the aorta including the valve. Closed and open valve surfaces, as well as the lumen aorta, are reconstructed directly from medical images using new ad hoc algorithms, allowing a patient-specific simulation. The fluid dynamics problem that accounts from the movement of the valve is solved by a new 3D-0D fluid-structure interaction model in which the valve surface is implicitly represented through level set functions, yielding, in the Navier-Stokes equations, a resistive penalization term enforcing the blood to adhere to the valve leaflets. The dynamics of the valve between its closed and open position is modeled using a reduced geometric 0D model. At the discrete level, a finite element formulation is used and the SUPG stabilization is extended to include the resistive term in the Navier-Stokes equations. Then, after time discretization, the 3D fluid and 0D valve models are coupled through a staggered approach. This computational framework, applied to a patient-specific geometry and data, allows to simulate the movement of the valve, the sharp pressure jump occurring across the leaflets, and the blood flow pattern inside the aorta.

关键词： Aortic valve image-based modeling Patient-specific simulation Computational fluid dynamics Finite element method Heart modeling

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Numerical analysis of wall shear stress in ascending aorta before tearing in type A aortic dissection

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COMPUTERS IN BIOLOGY AND MEDICINE 2017年 89卷 236-247页

作者： Chi, Qingzhuo He, Ying Luan, Yong Qin, Kairong Mu, Lizhong Dalian Univ Technol Minist Educ Key Lab Ocean Energy Utilizat & Energy Conservat Dalian 116024 Peoples R China Dalian Med Univ Affiliated Hosp 1 Dept Anesthesiol Dalian 116011 Peoples R China Dalian Univ Technol Dept Biomed Engn Dalian 116024 Peoples R China

Although the incidence of many cardiovascular diseases has declined as medical treatments have improved, the prevalence of aortic dissection (AD) has increased. Compared to type B dissections, type A dissections are more severe, and most patients with type A dissections require surgical treatment. The objective of this study was to investigate the relationships between the wall shear stress (WSS) on the aortic endothelium and the frequent tearing positions using computational fluid dynamics. Five type A dissection cases and two normal aortas were included in the study. First, the structures of the aortas before the type A dissection were reconstructed on the basis of the original imaging data. Analyses of flow in the reconstructed premorbid structures reveals that the rupture positions in three of the five cases corresponded to the area of maximum elevated WSS. Moreover, the WSS at the junction of the aortic arch and descending aorta was found to be elevated, which is considered to be related to the locally disturbed helical flow. Meanwhile, the highest WSS in the patients with premorbid AD was found to be almost double that of the control group. Due to the noticeable morphological differences between the AD cases and the control group, the WSSs in the premorbid structures without vasodilation in the ascending part were estimated. The computational results revealed that the WSS was lower in the aorta without vasodilation, but the pressure drop in this situation was higher than that with vasodilation in the ascending aorta. Significant differences were seen between the AD cases and the control group in the angles of the side branches of the aortic arch and its bending degree. Dilation of the ascending aorta and alterations in the branching angles may be the key determinants of a high WSS that leads to type A dissection. Greater tortuosity of the aortic arch leads to stronger helical flow through the distal aortic arch, which may be related to tears in this region.

关键词： Aortic dissection Wall shear stress Patient-specific model Structured mesh generation Computational fluid dynamics image-based modeling

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Mitral Valve Chordae Tendineae: Topological and Geometrical Characterization

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ANNALS OF BIOMEDICAL ENGINEERING 2017年第2期45卷 378-393页

作者： Khalighi, Amir H. Drach, Andrew Bloodworth, Charles H. Pierce, Eric L. Yoganathan, Ajit P. Gorman, Robert C. Gorman, Joseph H., III Sacks, Michael S. Univ Texas Austin Inst Computat Engn & Sci Ctr Cardiovasc Simulat Dept Biomed Engn Austin TX 78712 USA Georgia Inst Technol Cardiovasc Fluid Mech Lab Wallace H Coulter Dept Biomed Engn Atlanta GA 30332 USA Univ Penn Dept Surg Gorman Cardiovasc Res Grp Philadelphia PA 19104 USA

Mitral valve (MV) closure depends upon the proper function of each component of the valve apparatus, which includes the annulus, leaflets, and chordae tendineae (CT). Geometry plays a major role in MV mechanics and thus highly impacts the accuracy of computational models simulating MV function and repair. While the physiological geometry of the leaflets and annulus have been previously investigated, little effort has been made to quantitatively and objectively describe CT geometry. The CT constitute a fibrous tendon-like structure projecting from the papillary muscles (PMs) to the leaflets, thereby evenly distributing the loads placed on the MV during closure. Because CT play a major role in determining the shape and stress state of the MV as a whole, their geometry must be well characterized. In the present work, a novel and comprehensive investigation of MV CT geometry was performed to more fully quantify CT anatomy. In vitro micro-tomography 3D images of ovine MVs were acquired, segmented, then analyzed using a curve-skeleton transform. The resulting data was used to construct B-spline geometric representations of the CT structures, enriched with a continuous field of cross-sectional area (CSA) data. Next, Reeb graph models were developed to analyze overall topological patterns, along with dimensional attributes such as segment lengths, 3D orientations, and CSA. Reeb graph results revealed that the topology of ovine MV CT followed a full binary tree structure. Moreover, individual chords are mostly planar geometries that together form a 3D load-bearing support for the MV leaflets. We further demonstrated that, unlike flow-based branching patterns, while individual CT branches became thinner as they propagated further away from the PM heads towards the leaflets, the total CSA almost doubled. Overall, our findings indicate a certain level of regularity in structure, and suggest that population-based MV CT geometric models can be generated to improve current MV repa

关键词： Mitral valve image-based modeling Curveskeleton representation Reeb graphs Full binary tree Population-representative statistics

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Multiview Visibility Estimation for image-based modeling

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Journal of Computer Science & Technology 2011年第6期26卷 1000-1010页

作者：张柳新裴明涛贾云得 CCF Beijing Laboratory of Intelligent Information Technology School of Computer ScienceBeijing Institute of Technology

In this paper, we investigate the problem of determining regions in 3D scene visible to some given viewpoints when obstacles are present in the scene. We assume that the obstacles are composed of some opaque objects with closed surfaces. The problem is formulated in an implicit framework where the obstacles are represented by a level set function. The visible and invisible regions of the given viewpoints are determined through an efficient implicit ray tracing technique. As an extension of our approach, we apply the multiview visibility estimation to an image-based modeling technique. The unknown scene geometry and multiview visibility information are incorporated into a variational energy functional. By minimizing the energy functional, the true scene geometry as well as the accurate visibility information of the multiple views can be recovered from a number of scene images. This makes it feasible to handle the visibility problem of multiple views by our approach when the true scene geometry is unknown.

关键词： visibility estimation image-based modeling multiple views level set implicit surface

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Patterns from photograph: Reverse-engineering developable products

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COMPUTERS & GRAPHICS-UK 2017年 66卷 4-13页

作者： Fondevilla, Amelie Bousseau, Adrien Rohmer, Damien Hahmann, Stefanie Cani, Marie-Paule Univ Grenoble Alpes CNRS LJK INRIA Grenoble France Univ Cote Azur INRIA Sophia Antipolis France Univ Lyon CPE Lyon Lyon France

Developable materials are ubiquitous in design and manufacturing. Unfortunately, general-purpose modeling tools are not suited to modeling 3D objects composed of developable parts. We propose an interactive tool to model such objects from a photograph. Users of our system load a single picture of the object they wish to model, which they annotate to indicate silhouettes and part boundaries. Assuming that the object is symmetric, we also ask users to provide a few annotations of symmetric correspondences. The object is then automatically reconstructed in 3D. At the core of our method is an algorithm to infer the 2D projection of rulings of a developable surface from the traced silhouettes and boundaries. We impose that the surface normal is constant along each ruling, which is a necessary property for the surface to be developable. We complement these developability constraints with symmetry constraints to lift the curve network in 3D. In addition to a 3D model, we output 2D patterns enabling to fabricate real prototypes of the object on the photo. This makes our method well suited for reverse engineering products made of leather, bent cardboard or metal sheets. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Single-view 3D reconstruction image-based modeling Sketch-based modeling Developable surfaces

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Interactive Relighting in Single Low-Dynamic Range images

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ACM TRANSACTIONS ON GRAPHICS 2017年第2期36卷 1–18页

作者： Wu, Jung-Hsuan Saito, Suguru Tokyo Inst Technol Sch Comp Meguro Ku W8-702-12-1 Oookayama Tokyo 1528552 Japan

This article addresses the relighting of outdoor and large indoor scenes illuminated by nondistant lights, which has seldom been discussed in previous works. We propose a method for users to interactively edit the illumination of a scene by moving existing lights and inserting synthetic lights into the scene that requires only a small amount of user annotation and a single low-dynamic range (LDR) image. We achieve this by adopting a top-down approach that estimates the scene reflectance by fitting a diffuse illumination model to a photograph. This approach gains stability and robustness by estimating the camera, scene geometry, and light sources in sequence and by using a confidence map, which is a per-pixel weight map. The results of our evaluation demonstrates that the proposed method can estimate a scene accurately enough for realistic relighting of images. Moreover, the experimental results of our user studies show that the synthesized images are so realistic as to be almost indistinguishable from real photographs.

关键词： image-based relighting image-based modeling

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