GPUFLIC: interactive and accurate dense visualization of unsteady flows

In this paper we present GPU-based techniques for the interactive visualization of large unsteady 3D flow fields on uniform grids. We propose a novel dual-core approach to asynchronously stream such fields from the CPU, thus enabling the efficient exploration of large time-resolved sequences. This approach decouples visualization from data handling, resulting in interactive frame rates. Built upon a previously published GPU particle engine for flow visualization we have developed new strategies to compute and to visualize path lines and streak lines on the GPU. To provide additional visual cues, focus+context techniques for polygonal meshes have been integrated. The proposed techniques are used in the visual analysis of the Terashake 2.1 earthquake simulation data, and they have been shown to be very effective in revealing the relevant information in this data.

We propose unsteady flow advection-convolution (UFAC) as a novel visualization approach for unsteady flows. It performs time evolution governed by pathlines, but builds spatial correlation according to instantaneous streamlines whose spatial extent is controlled by the flow unsteadiness. UFAC is derived from a generic framework that provides spacetime-coherent dense representations of time dependent-vector fields by a two-step process: 1) construction of continuous trajectories in spacetime for temporal coherence; and 2) convolution along another set of paths through the above spacetime for spatially correlated patterns. Within the framework, known visualization techniques-such as Lagrangian-Eulerian advection, image-based flow visualization, unsteady flow LIC, and dynamic LIC-can be reproduced, often with better image quality, higher performance, or increased flexibility of the visualization style. Finally, we present a texture-based discretization of the framework and its interactive implementation on graphics hardware, which allows the user to gradually balance visualization speed against quality.

We propose a scheme for modeling point sample geometry with statistical analysis. In our scheme we depart from the current schemes that deterministically represent the attributes of each point sample. We show how the statistical analysis of a densely sampled point model can be used to improve the geometry bandwidth bottleneck and to do randomized rendering without sacrificing visual realism. We first carry out a hierarchical principal component analysis (PCA) of the model. This stage partitions the model into compact local geometries by exploiting local coherence. Our scheme handles vertex coordinates, normals, and color. The input model is reconstructed and rendered using a probability distribution derived from the PCA analysis. We demonstrate the benefits of this approach in all stages of the graphics pipeline: (1) orders of magnitude improvement in the storage and transmission complexity of point geometry, (2) direct rendering from compressed data, and (3) view-dependent randomized rendering.

In this paper a fast and robust method is proposed to search a large video collection for given short clips. Compared with existing video searching methods which use visual features only, our scheme performs a two-phase hierarchical matching technique using visual and audio features successively. Considering that video sampling rate (25 or 30 fps) is much lower than that of audio (8 to 48 kHz), a coarse search is implemented with sub-sampled video frames first, and then potential matches are verified and accurately located using fine audio features. Both features are extracted directly from MPEG compressed video for computational efficiency. Experiments have been conducted on over 10.5 hours of video to search for re-occurrences of 83 TV commercials and one news lead-out clip. All the 220 instances are correctly detected with no false alarm. Our experiments also show that the proposed method is robust to variations of video bit rate, frame rate, frame size and color shifting.

With the growing interest of integrating robotics into everyday life and industry, the requirements towards the quality and quantity of applications grows equally hard. This trend is profoundly recognized in applications involving visual perception. Whereas visual sensing in home environments tend to be mainly used for recognition and localization, safety becomes the driving factor for developing intelligent visual control algorithms. More specifically, a robot operating in a human environment should not collide with obstacles and executed motion should be as smooth as possible. Furthermore, as the environment is not known on beforehand, a high demand on the robustness of visual processing is a necessity. On the other hand, in an industrial setting, the environment is known on beforehand and safety is mainly guaranteed by excluding a human operator. Despite these reasons, and the fact that visual servoing has gained much attention from industry to become a standard solution for robotic automation tasks, applications are highly simplified. For example, methods such as visual fault detection are already a mature technique in industrial manufacturing, where a fixed camera observes a product (e.g., on a conveyor belt) and checks whether it meets certain requirements. These operations can be executed at a fairly high rate due to the simplicity of the system (e.g., static camera) and the simplification of the processing task (e.g., binary images). For both areas the identified difficulties are similar. Foremost, this is the slow nature of (robust) visual processing, in respect to the ever growing demand of increasing speed and reducing delay. These two application areas with analogous limitations motivate the design of more direct approaches of vision in visual control systems. Therefore, in order to meet the requirements for next generation visual control systems, this thesis presents approaches which employ visual measurements as a direct feedback to design constrained motion. First, for industrial robotics, in order to obtain the required positioning accuracy, the measurement and fixation system have to be highly rigid and welldesigned, implying high cost and long design time. By measuring the position of objects directly with a camera, instead of indirectly by motor encoders, the requirements of the measurement and fixation system are less demanding. Moreover, this motivates the miniaturization of the complete control system. The approach is validated in experiments on a simplified 2D planar stage (i.e., considerable friction, poor fixation), which attains similar performance compared to encoder-based positioning systems. Secondly, in a human-centred environment, this direct sensing can improve traditional visual control systems, when subject to certain disturbances. More specifically, a method is proposed that uses an image-based feedforward controller on top of traditional position-based visual servo control to overcome disturbances such as friction or poorly designed local motor controllers. This visual feedforward control action is only active when an image-based error is present and vanishes when that error goes to zero. The method is validated on an anthropomorphic robotic manipulator with 7 degrees of freedom, intended for operation in the human care environment. Third, sensing the product directly gives rise to designing motion directly. Whereas in traditional approaches the motion trajectory is designed offline and can not be changed at runtime, direct trajectory generation computes the motion of the next step based on current state and events. This means that at any instance in time, the trajectory of a motion system can be altered with respect to certain desired kinematic or dynamic constraints. For industrial applications this makes manufacturing on near-repetitive or non-rigid structures (e.g. flexible displays) possible. When applied to a robotic manipulator, this enables obstacle avoidance to no longer be on path planning level, but on trajectory planning level, where kinematic or dynamic constraints can be taken into account. This results in a motion that is smoother than when obstacle avoidance with path planning is employed. For both application areas this direct trajectory generation method is implemented and shows high flexibility in constrained motion trajectory design.

The near-wake region over the rear of sedan automobiles is characterised by unsteady flows. Until now, a comprehensive model for the structure of the near-wake has not been found. This thesis will provide a novel near-wake flow model for sedan automobiles. It will also provide both qualitative and quantitative evidence that the near-wake flow structure, over the rear of sedan automobiles has many similar characteristics to basic two-dimensional separating/reattaching flows. Three-dimensional flow in the near-wake region of automobiles provides many challenges for researchers. Investigation of the near-wake region required a novel approach in order to record useful, high quality data. Implementation of a wide range of experimental procedures, and several novel experimental techniques, allowed the determination of the unsteady near-wake structure. Time-averaged skin friction patterns over various sedan automobiles were analysed, and through the application of critical point theory the time-averaged near-wake structure was determined. Detailed time-dependent flow visualisation was performed using real­ time recording techniques of seeded flow and tuft patterns. Time-dependent flow visualisation provided the basis for the construction of an unsteady near-wake flow model. Quantitative measurements included high-frequency simultaneous surface pressure measurements, synchronised with unsteady wake probe measurements. These measurements defined the unsteady characteristics of the near-wake. The unsteady near-wake was found to consist of a large vortex. This vortex is characterised by its hairpin shape and is regularly shed from the near-wake at a Strouhal frequency of approximately 0.41. The separation region was also found to have a low­ frequency unsteadiness at a Strouhal frequency of approximately O.11. The normalisation length of both these Strouhal frequencies is the horizontal separation length. Hence, a new method of separation length determination over sedan automobiles was found. The near-wake flow was also found to consist of reverse flow directed toward the separation location. The near-wake structure, periodicity and characteristic length dimension were found to closely match those found in other separating reattaching flows. The two-dimensional backward facing step, bluff leading edge separations and separating flow from low-aspect ratio aerofoils were all found to consist of similar wake topologies. Direct similarities were also found with time-averaged fastback automobile near-wakes. Hence, suggesting a universal near-wake model. Determination of the near-wake structure over the rear of automobiles will provide the framework for efficient and advanced development of automobile shapes. Minimisation of automobile drag, increased ride comfort and improved automobile stability can now be approached from a position of knowledge. The work contained in this thesis will provide the basis for further detailed investigation, and provide a benchmark for validation of computational codes.

The solution of tridiagonal system of equations using graphic processing units (GPU) is assessed. The parallel-Thomas-algorithm (PTA) is developed and the solution of PTA is compared to two known parallel algorithms, i.e. cyclic-reduction (CR) and parallel-cyclic-reduction (PCR). Lid-driven cavity problem is considered to assess these parallel approaches. This problem is also simulated using the classic Thomas algorithm that runs on a central processing unit (CPU). Runtimes and physical parameters of the mentioned GPU and CPU algorithms are compared. The results show that the speedup of CR, PCR and PTA against the CPU runtime is 4.4x,5.2x and 38.5x, respectively. Furthermore, the effect of coalesced and uncoalesced memory access to GPU global memory is examined for PTA, and a 2x-speedup is achieved for the coalesced memory access. Additionally, the PTA performance in a time dependent problem, the unsteady flow over a square, is assessed and a 9x-speedup is obtained against the CPU.

Objective To observe the changes in visual field defect before and after treatment in patients with acute solitary occipital lobe cerebral infarction. Methods From January 2017 to May 2019, 59 patients with hemianopsia who were diagnosed as acute occipital lobe cerebral infarction in Henan Provincial People's Hospital were selected. There were 35 males (59.3%) and 24 females (40.7%); aged from 50 to 72 years, with an average age of 62.86±6.10 years. There were 23 patients of right occipital cerebral infarction and 36 patients of left occipital cerebral infarction. Lesions involved 41 patients in the striated area, 8 patients involved the occipital pole, and 23 patients involved visual radiation. All patients underwent standard medical treatment. All patients underwent visual field examination before treatment, and modified rankin scale (mRS) was used to evaluate the level of visual disability after cerebral infarction. At 1, 3, and 6 months after treatment,54 patients underwent at least one visual field examination in outpatient or inpatient follow-up visits, and 5 patients were lost to follow-up; 49 patients received repeated mRS scores. The visual field defect and mRS score of patients before and after treatment were compared and analyzed. The improvement of visual field defect in the horizontal direction exceeding 10°or the vertical direction exceeding 15°was defined as improvement, otherwise it was defined as no improvement. According to the type of visual field defect, the patients were divided into two groups: complete homonymous hemianopia and incomplete homonymous hemianopia. The cumulative visual field improvement rate of the two groups of patients was calculated. An mRS score of 0 to 2 was defined as a good prognosis, and >2 was defined as a poor prognosis. Results Before treatment, of the 59 patients, 47 were complete homonymous hemianopsia and 12 were incomplete. Of the 47 patients with complete homonymous hemianopia, 26 patients had hemianopia on the right side of both eyes, 21 patients had hemianopia on the left side of both eyes; 32 patients with macular avoidance (72.3%). Among the 12 patients of incomplete homonymous hemianopia, 10 patients of quadrant blindness included 6 patients of upper quadrant and 4 patients of lower quadrant; 2 patients of partial isotropic hemianopia on one side. Of the 54 patients reviewed after treatment, the visual field improved at the last follow-up of 25 patients (46.3%), and there was no improvement in 29 patients (53.7%). The cumulative visual field improvement rate of 47 patients with complete hemianopia hemianopia before treatment was 37.2% (16/43). The cumulative visual field improvement rate of 11 patients with incomplete isotropic hemianopia before treatment was 81.8% (9/11). There was a statistically significant difference in cumulative visual field improvement between the two groups of patients (χ2 = 7.011, P<0.05). Before treatment, 59 patients had mRS scores of 1 to 2 points in 15 patients (25.4%), and 44 patients with 2 points or more (74.6%). Of the 49 patients reviewed after treatment, 28 (57.1%) had a good prognosis and 21(42.9%) had a poor prognosis. Conclusions The visual field defect of patients with homonymous hemianopsia after acute occipital infarction may be improved after treatment. The improvement mostly occurs within 1 m after treatment, and patients with incomplete homonymous hemianopsia have more significant improvements than those with complete homonymous hemianopsia. Key words: Occipital lobe; Cerebral infarction; Visual fields; Hemianopsia

Visual orientation is precise and accurate, when the observer is upright, in the absence of any visual surround cues. Lateral tilt of the body relative to gravity results in a close approximation of the visual and gravitational reference axes. There are, however, relatively small, systematic differences between them. For body tilts less than 70° the visual vertical is located on the opposite side of the gravitational vertical to tilt, whereas the reverse occurs with greater degrees of tilt. These are referred to as the E- and A-effects, respectively. The precision of visual orientation with body upright was confirmed by experiments reported in this thesis, and it was not changed by variations in the stimulus or procedural conditions. However, the visual vertical was influenced by the eye used for observation. The hypothesis that visual orientation is a function of retinal orientation was examined. This hypothesis was rejected because stimulation of various postural systems, while maintaining the head upright, resulted in systematic variations in visual orientation. It was considered that the accuracy of visual orientation with body upright is due to the precise postural information for this orientation. [...]

We propose a new technique to visualize dense vector fields associated with unsteady fluid flows. This technique is based on a Lagrangian-Eulerian Advection (LEA) scheme, and it enables animations with high spatio-temporal correlation at interactive rates. We demonstrate the efficiency and efficacy of the technique in applications to numerical simulation of a shock interacting with a longitudinal vortex, and of ocean circulation in the Gulf of Mexico. The simplicity of the data structures and the facility of implementation suggest that LEA could become a useful component of any scientific visualization toolkit concerned with the display of unsteady flows.

Ubiquitous access to internet has resulted in more and more people going online to get their daily dose of news. In a 2010 survey conducted by the Pew Project for Excellence in Journalism, 41% of the respondents said they get most of their news online, 10% more than those who said they got most of their news from a newspaper. A lot of socio-technical factors have contributed to this phenomenal rise in adoption of online news in recent years. One of the biggest reasons why people are increasingly reading news online is because it facilitates discussion with peers (Nguyen 2010), offering different viewpoints which aid in forming a rounded personal opinion about the news story. The Pew survey found that 37% of online news users (and 51% of 18-29 year olds) think that commenting on news stories is an important feature to have. A lot of people tend to shape their opinion by reading discussion comments, reflective articles, blogs and even tweets about the news. Hence, an increasing number of people rely on online sources of news – be it news websites or news aggregator services like Digg, Reddit, Google Reader, Flipboard, Pulse etc. The problem with these news websites and aggregators is that the only way people can gather public opinion is by actively searching through the endless stream of comments and feeds, filtering out spam (which is a growing problem) and then reading the relevant posts. A top trending story on Twitter will typically see multiple tweets per second, and keeping up with the rapid flow of incoming tweets is quite cumbersome and cognitively taxing. Hence it becomes increasingly difficult and time consuming for someone who wants to get the pulse of the people affected by a news story. Furthermore, in certain scenarios people might want to look at more fine grained opinions. Currently, there is no elegant way to extract geographic and demographic impact of a news story. What is the public sentiment in Indonesia about the Arab Spring? How did the public opinion about the Wikileaks disclosures change as the story unfolded during the course of a year? It is very difficult and tedious to observe such patterns using the currently available news providers. This work attempts to solve these problems by proposing a news aggregator platform which pulls news stories from various sources and also aggregates public responses, reflections, opinions and sentiments associated with those stories. This data is presented in ways that are easily understandable so readers can make better sense of the stories unfolding across the globe. Such a news aggregator platform that gathers and display public opinion and sentiments about a story, must deal with various challenges – 1. Opinions are very subjective. Different people feel about a story in different ways. With such an enormous amount of diverse opinions and subjectivity, how can we possibly aggregate the responses into something that makes sense as a whole? ________________________________ Acknowledgements: Prof. Yardi, S. for the guidance Sethi, P. (2013). Public opinion aggregation by annotation and tagging of online news stories. iConference 2013 Proceedings (pp. 891-894). doi:10.9776/13453 Copyright is held by the author. iConference 2013 February 12-15, 2013 Fort Worth, TX, USA 892 2. There isn’t really a unified web standard for expressing opinion (in textual form). Some people tweet in 140 characters, while others write elaborate blog posts. Some websites employ tags which a reader can use to define and classify their public opinion, while others rely on threaded comments and comment ranking systems. How can a platform be flexible enough to adapt to all these varied standards so that it can extract valuable data from various sources? Perhaps the platform can create a new standard of expression on the web which is flexible and comprehensive enough to be used to express diverse views about every news story in the world. 3. How to filter out spam while extracting public opinion? 4. Once the platform has access to the data it needs, how should it be displayed to the reader in a way that makes sense? What forms of visualizations, illustrations and graphical representations can be employed to give the reader a holistic view of how people feel about a story? 5. How can the platform determine and convey effects of geographical, demographic and temporal variations as the story unfolds? These are just a few out of possibly many issues which must be dealt with. Previous research on similar public opinion aggregation services has greatly focused on natural language processing, data mining and text categorization and clustering. Xiaojun (2010) proposed a framework for crawling the web for comments and applying various data mining algorithms on the data to extract relevant information. Diakopoulos and Shamma (2010) used tweets posted in conjunction with the live presidential debate between Barack Obama and John McCain to gauge public opinion. Brody and Diakopoulos (2011) studied the use of word lengthening to detect sentiment in microblogs. This research proposes a solution – The Opinionated Reader, which relies on sentiment tags and annotations associated with a news story. The essential idea is to create a commenting, discussion and sharing plug-in which can be used by news websites and aggregators as a commenting solution for their news pages. Users wanting to share or comment on a news story through the plug-in are asked to tag the news story with sentiment tags and annotate the story with their reaction (happy/positive or sad/negative). These tags and annotations are stored, aggregated and linked to each news story. A mobile application provides the front-end interface for users to access the news stories and the aggregated sentiment associated with each story. The basic architecture is explained as follows: The Opinionated Reader – Mobile/Tablet App The app fetches news articles from various web sources, based on the interests and preferences configured by the user. In every news article, a portion of the screen real estate is reserved for Opinions which shows graphical visualizations and illustrations of the public opinion surrounding the news story. These visualizations include: A Sentiment Graph indicating the popular tags associated with the story (E.g.: “Shocking”, “Inspiring”, “Amusing” etc.). See Figure 1 for example visualization. A Positivity Graph which plots the level of positivity associated with the story on a time scale from when the news broke. See Figure 2 for example visualization. Figure 1. Example Sentiment Graph Figure 2. Example Positivity Graph iConference 2013 February 12-15, 2013 Fort Worth, TX, USA 893 The user can choose to see these visualizations for a particular time period in the evolution history of the news story, or for a specific country. The app also facilitates people to tag and annotate news articles from within its interface. The Opinionated Reader – Commenting and Sharing Web Plug-in These days, a common way of adding discussion and commenting functionality to news websites is by using 3 rd party services (like DISQUS). The Opinionated Reader is a similar service which can be embedded into the news articles of various news websites to enable commenting and sharing. When someone wishes to comment on an article, the comment is directed through this plug-in, which allows the users to annotate the article with the sentiment tags and reactions along with their comments. The Opinionated Reader saves this information along with the commenter’s location and date of comment (See Figure 3). Figure 3. The Opinionated Reader Web Plug-in 'Add Comment' dialog mockup The Opinionated Reader – Back-end The Back-end maintains a database of news items extracted from RSS feeds of various news websites. Each news article is linked with the sentiment tags and reaction/positivity annotations extracted from the comments and annotations gathered by the commenting plug-in. This data is used by the mobile/tablet app to generate visualizations (Sentiment Graph and Positivity Graph). The back-end also performs data mining on the tags and annotations for geographies and tracks the opinions across time. The back end system responds to queries received from the mobile app with the news story and associated tags and annotations, which are then rendered by the mobile app for the user. iConference 2013 February 12-15, 2013 Fort Worth, TX, USA 894 Discussion and Conclusion This design idea is still in a nascent state and has long hours of research, brainstorming, designing and development to go before it can be realized into something tangible. Twitter has grown exponentially in importance as a news source and it would be vastly valuable to integrate Twitter with The Opinionated Reader. Possibilities include use of special hash tags and natural language processing of tweets to extract public sentiment. The current design supports only two reaction annotations – positive and negative. Not every news story fits this annotation paradigm. Further research about human reactions to news stories might unveil interesting insights which would help zero in on a more robust annotation rubric. Lastly, since this service is envisioned to be non-curated and non-moderated, the value served by the app depends on the users themselves. Greater adoption will lead to more annotations and tags, which translates into a more accurate public opinion as presented to the user.

Objective To investigate the visual field characteristics of patients with anterior ischemic optic neuropathy (AION) and idiopathic optic neuritis (ION) , and explore the occurrence mechanism. Methods The visual field data of patients with AION and idiopathic demyelinating optic neuritis (ION) diagnosed and treated in the Ophthalmology Department of Zhengzhou People’s Hospital from January 2015 to June 2018 were compared. The patient’s gender, age composition, best corrected visual acuity (BCVA), visual field date, pupil size at the time of examination, visual field defect type, location, visual field mean defect (MD), and mode defect (PSD) were recorded. Results There were 36 cases (40 eyes) with AION and 29 cases (33 eyes) with ION. There were significant differences in the mean age, the gender composition, BCVA, the visual field testing duration, the pupil sizes, MD and PSD between these two groups (P<0.05). Conclusions AION and ION are similar in clinical symptoms, but the visual field of the two is more diverse. It is closely related to the pathogenesis of the disease, so it differential diagnosis of the two diseases can be achieved by visual field examination. Key words: Anterior ischemic optic neuropathy; Idiopathic optic neuritis; Visual field

This paper proposed an organization method of laser point cloud data for the efficient management and rapid visualization of the massive point cloud data of vehicle-mounted laser scanner. In this paper, both the original point cloud data and its trajectory are sectioned for the fast indexing firstly, then the LOD(levels of details) index of each section is build based on octree structure. With a tile type and multiresolution storage mode based on folder system, the depth of octree structure is represented by the level of folder directory, and in every node folder, the corresponding point cloud data file and its node properties file are both include. The storage method of this paper decreases the preprocessing time greatly and can support concurrent access owing to mutually independence of each node. Moreover, with the application of view frustum culling technology and multi-thread dynamic dispatch technology, the rendering and roaming of massive point cloud can realize real time updating according to viewpoint change, which significantly improves the dispatch efficiency of vehicle-mounted laser point cloud data. In the experiment, our method was compared with several popular software of point cloud data processing (e.g. XGRT, Quick Terrain Reader) on the data dispatch. The results show our method has obvious advantage on storage capacity, data access time, memory footprint, rendering frame rate and so on, it indicates our method is effective for the management of vehicle-mounted laser point cloud data and can improve the production efficiency for indoor-work of vehicle-mounted laser point cloud data processing.

The graphics processing unit (GPU) has evolved from configurable graphics processor to a powerful engine for high performance computer. In this paper, we describe the graphics pipeline of GPU, and introduce the history and evolution of GPU architecture. We also provide a summary of software environments used on GPU, from graphics APIs to non-graphics APIs. At last, we present the GPU computing in computational fluid dynamics applications, including the GPGPU computing for Navier-Stokes equations methods and the GPGPU computing for Lattice Boltzmann method.

In contradiction to the crossing of all retinal fibers in the lateral-eye species, the retinal fibers of binocular vision in frontal-eye species run either ipsilaterally or cross the midline twice to terminate the ipsilateral cerebral hemisphere.[1][1] It is hypothesized that carrying separated