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Optimal constrained multi-degree reduction of Bézier curves with explicit expressions based on divide and conquer

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第4期10卷 577-582页

作者： Lian ZHOU Guo-jin WANG Institute of Computer Graphics and Image Processing State Key Lab of CAD & CG Zhejiang University Hangzhou 310027 China

We decompose the problem of the optimal multi-degree reduction of Bézier curves with corners constraint into two simpler subproblems, namely making high order interpolations at the two endpoints without degree reduction, and doing optimal degree reduction without making high order interpolations at the two endpoints. Further, we convert the second subproblem into multi-degree reduction of Jacobi polynomials. Then, we can easily derive the optimal solution using orthonormality of Jacobi polynomials and the least square method of unequally accurate measurement. This method of 'divide and conquer' has several advantages including maintaining high continuity at the two endpoints of the curve, doing multi-degree reduction only once, using explicit approximation expressions, estimating error in advance, low time cost, and high precision. More importantly, it is not only deduced simply and directly, but also can be easily extended to the degree reduction of surfaces. Finally, we present two examples to demonstrate the effectiveness of our algorithm.

关键词： Bezier curves Multi-degree reduction Divide and conquer

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A new method in highway route design:joining circular arcs by a single C-Bézier curve with shape parameter

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第4期10卷 562-569页

作者： Hua-hui CAI Guo-jin WANG Institute of Computer Graphics and Image Processing State Key Lab of CAD & CG Zhejiang University Hangzhou 310027 China

We constructed a single C-Bezier curve with a shape parameter for G^2 joining two circular arcs. It was shown that an S-shaped transition curve, which is able to manage a broader scope about two circle radii than the Bezier curves, has no curvature extrema, while a C-shaped transition curve has a single curvature extremum. Regarding the two kinds of curves, specific algorithms were presented in detail, strict mathematical proofs were given, and the effectiveness of the method was shown by examples This method has the following three advantages：（1） the pattern is unified; （2） the parameter able to adjust the shape of the transition curve is available; （3） the transition curve is only a single segment, and the algorithm can be formulated as a low order equation to be solved for its positive root. These advantages make the method simple and easy to implement.

关键词： Transition curve C-Bezier curve Monotone curvature Shape parameter

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Interactive simulation and visualization of fluids with surface raycasting

Interactive simulation and visualization of fluids with surf...

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23rd SIBGRAPI Conference on graphics, Patterns and images, SIBGRAPI 2010

作者： Inácio, Renan Teston Nobrega, Tiago H. C. Carvalho, Diego D. B. Von Wangenheim, Aldo LAPIX - Laboratory for Image Processing and Computer Graphics Federal University of Santa Catarina Florianópolis Brazil

ISBN: (纸本)9780769542300

We present a method to couple particle-based fluid simulation methods such as Smoothed Particle Hydrodynamics (SPH) and volume rendering in order to visualize the fluid. A volume is generated from the fluid's implicit density field so volume raycasting can be performed to render the surface on the GPU. The volume generation algorithm is also implemented in the GPU and is suitable to be used with both SPH simulations implemented on CPU and GPU. We compare different implementations of fluid simulation, demonstrating the modularity of the volume generation method and concluding that it can be used together with other particle-based simulation models and other volume rendering techniques. © 2010 IEEE.

关键词： graphics processing unit

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Simplified Simulation and Visualization of Tubular Flows with Approximate Centerline Generation

Simplified Simulation and Visualization of Tubular Flows wit...

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2009 22nd IEEE International Symposium on computer-Based Medical Systems, CBMS 2009

作者： Nobrega, Tiago H. C. Carvalho, Diego Dias Bispo Von Wangenheim, Aldo LAPIX - Laboratory for Image Processing and Computer Graphics UFSC - Federal University of Santa Catarina Florianópolis Santa Catarina Brazil

ISBN: (纸本)9781424448784

We present a method to efficiently simulate fluid flows through tubular structures such as pipes and blood vessels. The method relies on the structure's centerline and for that purpose we present an algorithm to generate an approximate centerline of a tubular structure defined by an ordinary polygonal mesh. As an additional benefit, this centerline provides approximations of measures about the tubular structure such as length of regions of interest and crosssection diameters. The fluid is simulated with the Smoothed Particle Hydrodynamics method and the fluid-structure interaction is simplified to provide interactive rates. The particles can be colored according to physical quantities to better visualize the evolution of the fluid's state in narrow and otherwise obstructed areas. © 2009 IEEE.

关键词： Fluid structure interaction

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A multi-layered development framework for medical imaging applications

A multi-layered development framework for medical imaging ap...

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2009 22nd IEEE International Symposium on computer-Based Medical Systems, CBMS 2009

作者： Silva, André Ferreira Bem Carvalho, Diego Dias Bispo Nóbrega, Tiago H. C. Inácio, Renan Teston Von Wangenheim, Aldo LAPIX - Laboratory for Image Processing and Computer Graphics UFSC - Federal University of Santa Catarina Florianópolis Santa Catarina Brazil

ISBN: (纸本)9781424448784

computer Aided Diagnostic comprises wide research areas with stability and reliability software requirements. We propose a set of libraries aiming to provide a development framework for medical applications. This framework's libraries, mostly written from scratch (e.g Core library), were developed for both medical imaging systems and general physical simulations. Their internal interactions tend to be transparent to the developer and easy to use at the same time while providing flexibility to interact with other codes. The robustness of the code is shown in complex applications like the medical workstation here exemplified, while its flexibility and fast prototyping characteristics are exemplified with some simple demonstrations. © 2009 IEEE.

关键词： Libraries

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Using acceleration data from smartphones to interact with 3D medical data

Using acceleration data from smartphones to interact with 3D...

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23rd SIBGRAPI Conference on graphics, Patterns and images, SIBGRAPI 2010

作者： De Souza, Mateus Carvalho, Diego Dias Bispo Barth, Peter Ramos, Jeferson Vieira Comunello, Eros Von Wangenheim, Aldo LAPIX - Laboratory for Image Processing and Computer Graphics Federal University of Santa Catarina Florianópolis Brazil Hochschule RheinMain Wiesbaden Germany

ISBN: (纸本)9780769542300

Accelerometers integrated in modern smartphones pave the way to intuitively use gestures for collaboratively controlling interactive applications. Using and holding smartphones has become natural and ensures user acceptance as well as intuitive handling. We focus on using accelerators in several smartphones at the same time to interactively control a medical imaging solution. To this end, we introduce a framework to collect, modify, and distribute acceleration sensor data from multiple smartphones and integrate it with a medical imaging system which results in an environment suitable for e.g. doctors reviewing and explaining diagnostic findings. We performed some experiments to evaluate the usability of this approach and present an ongoing research in adapting the smartphone interface to physical simulation applications. © 2010 IEEE.

关键词： Smartphones

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A robust color image watermarking scheme

A robust color image watermarking scheme

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IASTED International Conference on Visualization, Imaging and image processing, VIIP 2012

作者： Wahedul Islam, Md. Alzahir, Saif Computer Science Department Image Processing and Graphics Lab UNBC BC Canada

ISBN: (纸本)9780889869264

In this paper, we present an image watermarking scheme based on discrete wavelet transform and singular value decomposition (SVD) for color images. This scheme embeds the watermark into the luminance (Y) channel of YC bCR color space of the host image. The luminance image is decomposed up to four DWT levels. SVD is applied on the HL1-4 and LH1-4sub-bands of each level and pseudo random number (PRN) sequence is added to the singular values of their coefficients to produce what we call modified singular values. To obtain the modified HL and LH coefficients, we take the inverse of the SVD of the modified SVs. Finally, we perform the IDWT on the modified HL & LH coefficients as well as HH and LL coefficients to produce the watermarked Y channel image. Then, the modified luminance, Cb and Cr are combined to get the watermarked color image. Simulation results show that our watermark is robust against high JPEG compression, filtering, Gaussian-noise, resizing and other image processing attacks. In addition, this watermark is not susceptible to any false positive or detection of false reference watermark.

关键词： image watermarking

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Vehicular Perception Based on Inertial Sensing: A Structured Mapping of Approaches and Methods

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SN computer Science 2020年第5期1卷 1-24页

作者： Menegazzo, Jeferson von Wangenheim, Aldo Graduate Program in Computer Science (PPGCC) Image Processing and Computer Graphics Lab (LAPIX) Department of Informatics and Statistics (INE) Brazilian Institute for Digital Convergence (INCoD) Federal University of Santa Catarina (UFSC) Santa Catarina Florianópolis Brazil

In this paper, we present a structured literature mapping of the state-of-the-art of vehicular perception methods and approaches using inertial sensors. An in-depth investigation and classification were performed employing the results of a systematic literature review. The analysis focused on identifying methods that capture signals provided by inertial sensors such as accelerometers and gyroscopes to recognize transient or persistent events associated with the vehicle’s movement. We classified these events into vehicular exteroception, associated with potholes, cracks, speed bumps, pavement type, conservation state;and vehicular proprioception, associated with lane change, braking, skidding, aquaplaning, turning right or left. Through the comprehensive study of publications in a 7-year time window, in addition to the methods, we have also identified their dependency factors, hardware platforms and applications. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Driver behaviour Driving style Inertial sensors Intelligent transport systems Road conditions Road surface anomaly

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Speed Bump Detection Through Inertial Sensors and Deep Learning in a Multi-contextual Analysis

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SN computer Science 2023年第1期4卷 18页

作者： Menegazzo, Jeferson von Wangenheim, Aldo Graduate Program in Computer Science (PPGCC) Image Processing and Computer Graphics Lab (LAPIX) Brazilian National Institute for Digital Convergence (INCoD) Department of Informatics and Statistics (INE) Federal University of Santa Catarina (UFSC)-Florianópolis Santa Catarina Brazil

Speed bumps are vertical raisings of the road pavement used to force drivers to slow down to ensure greater safety in traffic. However, these obstacles have disadvantages in terms of efficiency and safety, where the presence of speed bumps can affect travel time and fuel consumption, cause traffic jams, delay emergency vehicles, and cause vehicle damage or accidents when not properly signaled. Due to these factors, the availability of geolocation information for these obstacles can benefit several applications in Intelligent Transportation System (ITS), such as Advanced Driver Assistance Systems (ADAS) and autonomous vehicles, allowing to trace more efficient routes or alert the driver of the presence of the obstacle ahead. Speed bump detection applications described in the literature employ cameras or inertial sensors, represented by accelerometers and gyroscopes. While camera-based solutions are mature with evaluation in different contextual conditions, those based on inertial sensors do not offer multi-contextual analyses, being mostly simple applications of proof of concept, not applicable in real-world scenarios. For this reason, in this work, we propose the development of a reliable speed bump detection model based on inertial sensors, capable of operating reliably in contextual variations: different vehicles, driving styles, and environments in which vehicles can travel to. For the model development and validation, we collect nine datasets with contextual variations, using three different vehicles, with three different drivers, in three different environments, in which there are three different surface types, in addition to variations in conservation state and the presence of obstacles and anomalies. The speed bumps are present in two different pavement types, asphalt and cobblestone. We use the collected data in experiments to evaluate aspects such as the influence of the placement of the sensors for vehicle data collection and the data window size. Afterwar

关键词： Autonomous vehicles Deep learning Inertial sensors Intelligent transport systems Road conditions Speed bump

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Simplified simulation and visualization of tubular flows with approximate centerline generation

Simplified simulation and visualization of tubular flows wit...

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Annual IEEE Symposium on computer-Based Medical Systems

作者： Tiago H. C. Nobrega Diego Dias Bispo Carvalho Aldo von Wangenheim LAPIX - Laboratory for Image Processing and Computer Graphics UFSC - Federal University of Santa Catarina Brazil LAPIX - Laboratory for Image Processing and Computer Graphics UFSC - Federal University of Santa Catarina Florianópolis Brazil

We present a method to efficiently simulate fluid flows through tubular structures such as pipes and blood vessels. The method relies on the structure's centerline and for that purpose we present an algorithm to generate an approximate centerline of a tubular structure defined by an ordinary polygonal mesh. As an additional benefit, this center-line provides approximations of measures about the tubular structure such as length of regions of interest and cross-section diameters. The fluid is simulated with the smoothed particle hydrodynamics method and the fluid-structure interaction is simplified to provide interactive rates. The particles can be colored according to physical quantities to better visualize the evolution of the fluid's state in narrow and otherwise obstructed areas.

关键词： Visualization Biomedical imaging Computational modeling computer simulation Fluid flow Mesh generation Solid modeling Medical simulation Magnetic resonance imaging Computed tomography

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