Shadow Volume Research Articles

Web-based simulation and motion planning for human-robot and multi-robot applications

ABSTRACT This paper introduces the human-robot and multi-robot programming and simulation capabilities of a web-based, open-source robot programming and simulation tool called Assembly. The tool supports scenarios with up to three robots and provides support for simulating human arms working closely with a robot. To facilitate the simulation of scenarios involving human-robot and robot-robot collaboration, the paper proposes an improved version of the neural network-based Adaptive Simplex Motion Planner, which is capable of performing motion planning at a rate of over 3500 Hz. The improved toolpath planner uses an obstacle avoidance approach that leverages ray casting and shadow volume teachniques. The new planner is evaluated on the basis of two human-robot and multi-robot simulation scenarios and the results are compared to those of the original algorithm.

Reconstructing 3D Human Pose from RGB‐D Data with Occlusions

AbstractWe propose a new method to reconstruct the 3D human body from RGB‐D images with occlusions. The foremost challenge is the incompleteness of the RGB‐D data due to occlusions between the body and the environment, leading to implausible reconstructions that suffer from severe human‐scene penetration. To reconstruct a semantically and physically plausible human body, we propose to reduce the solution space based on scene information and prior knowledge. Our key idea is to constrain the solution space of the human body by considering the occluded body parts and visible body parts separately: modeling all plausible poses where the occluded body parts do not penetrate the scene, and constraining the visible body parts using depth data. Specifically, the first component is realized by a neural network that estimates the candidate region named the “free zone”, a region carved out of the open space within which it is safe to search for poses of the invisible body parts without concern for penetration. The second component constrains the visible body parts using the “truncated shadow volume” of the scanned body point cloud. Furthermore, we propose to use a volume matching strategy, which yields better performance than surface matching, to match the human body with the confined region. We conducted experiments on the PROX dataset, and the results demonstrate that our method produces more accurate and plausible results compared with other methods.

Incidence and risk factor analysis for swelling after apical microsurgery.

BACKGROUNDSwelling after apical microsurgery is a postoperative reaction and may reduce quality of life during healing.AIMTo evaluate periapical swelling after apical microsurgery and determine potential risk factors.METHODSNinety-eight apical microsurgery patients were selected for this study. Before surgery, bone shadow volume and density of pathological tissue were measured by cone beam computed tomography. The other variables (age, gender, operative teeth number, fistula, preoperative swelling, drug use and preoperative root canal treatments) were assessed during examination. Swelling degree was confirmed by questionnaires for patients on postoperative days 1, 7, 14 and 21. Statistical analyses were performed to identify predictors for swelling.RESULTSMajority of patients reported moderate (45.9%) or severe (34.7%) swelling on day 1, and moderate (44.9%) or mild (45.9%) on postoperative day 7. Ninety-nine percent of patients had no or mild swelling on postoperative day 14. The average swelling level peaked on day 1 postoperatively and gradually decreased. Of statistical significance, age, bone shadow volume and density of pathological tissue acted as predictors of swelling (P < 0.05). However, there was no significant difference in gender, tooth number, fistula, preoperative swelling, drug use, or preoperative root canal treatments (P > 0.05).CONCLUSIONYounger patients with larger shadow volume and density were significantly more likely to develop swelling after apical microsurgery.

Comparison of Modern Omnidirectional Precise Shadowing Techniques Versus Ray Tracing

AbstractThis paper presents an in depth comparison of state‐of‐the‐art precise shadowing techniques for an omnidirectional point light. We chose several types of modern shadowing algorithms, starting from stencil shadow volumes, methods using traversal of acceleration structures to hardware‐accelerated ray‐traced shadows. Some methods were further improved – robustness, increased performance; we also provide the first multi‐platform implementations of some of the tested algorithms. All the methods are evaluated on several test scenes in different resolutions and on two hardware platforms – with and without dedicated hardware units for ray tracing. We conclude our findings based on speed and memory consumption. Ray‐tracing is the fastest and one of the easiest methods to implement with small memory footprint. The Omnidirectional Frustum‐Traced Shadows method has a predictable memory footprint and is the second fastest algorithm tested. Our stencil shadow volumes are faster than some newer algorithms. Per‐Triangle Shadow Volumes and Clustered Per‐Triangle Shadow Volumes are difficult to implement and require the most memory; the latter method scales well with the scene complexity and resolution. Deep Partitioned Shadow Volumes does not excel in any of the measured parameters and is suitable for smaller scenes. The source codes of the testing framework have been made publicly available.

Detection of Suspicious Timestamps in NTFS using Volume Shadow Copies

When a computer gets involved in a crime, it is the mission of the digital forensic experts to extract the left binary artifacts on that device. Among those artifacts, there may be some volume shadow copy files left on the Windows operating system. Those files are snapshots of the volume recorded by the system in case of a needed restore to a specific past date. Before this study, we did not know if the valuable forensic information hold within those snapshot files can be exploited to locate suspicious timestamps in an NTFS formatted partition. This study provides the reader with an inter-snapshot time analysis for detecting file system timestamp manipulation. In other words, we will leverage the presence of the time information within multiples volume shadow copies to detect any suspicious tampering of the file system timestamps. A detection algorithm of the suspicious timestamps is contributed. Its main role is to assist the digital investigator to spot the manipulation if it has occurred. In addition, a virtual environment has been set up to validate the use of the proposed algorithm for the detection.

Effect of early whole lung lavage at different time-points for promoting the removal of depleted uranium from the lung

Purpose This study compared the effect of whole lung lavage (WLL) at different time-points early after exposure of the respiratory system to insoluble radioactive particles. Materials and methods Forty adult beagles were randomized into a control group and the 3-h, 8-h, 24-h, and 48-h lavage groups (n = 8). A canine model of acute lung injury was established by spraying a depleted uranium (DU) suspension using a superfine fiber bronchoscope, at a dose of 20 mg/kg. The lavage groups were subjected to WLL at 3 h, 8 h, 24 h, and 48 h post-DU exposure, while the control group received no treatment after exposure. Measurement of U in serum was performed using inductively coupled plasma mass spectrometry; measurements in the lavage fluid and left lung tissue were performed using inductively coupled plasma atomic emission spectrometry. The color of the lavage fluid was analyzed using colorimetry, and shadow changes in the lung were observed using chest computed tomography (CT). Results The lavage groups showed similarly increasing trends for serum U levels from DU exposure to 3 and 7 days after exposure; however, these values were significantly lower than those in the control group (p < .01). The U content in the lavage fluid was significantly higher in the 3-h group than in the 8-h, 24-h, and 48-h groups (p < .01), while that in the 8-h group was markedly higher than those in the 24-h and 48-h groups (p < .05). The average clearance rate of DU in the lungs varied in the range of 0.63‒7.06%. The U content in the left lung tissue of each lavage group was significantly lower than that in the control group (p < .01), while the content in the 8-h, 24-h, and 48-h groups was significantly higher than that in the 3-h group (p < .05). The colorimetric score of the lavage fluid in the 3-h group was significantly lower than those in the 8-h, 24-h, and 48-h groups (p < .05). Chest CT showed different degrees of consolidation and ground glass shadow changes in all groups. The score of the left lung shadow volume in the 3-h group was significantly lower than in the control, 8-h, 24-h, and 48-h groups (p < .01), while the score in the 8-h group was significantly higher than those in the 48-h and control groups (p < .05). Conclusions The best effect of WLL after exposure of the respiratory system to insoluble radioactive particles was achieved at 3 h, followed by 8 h; there was no difference in the effectiveness of lung lavage at 24 h and 48 h.

The ways of solving the problem of Ukraine's economy de-shadowing

Shadow economy is very common in the modern economy and inherent in any state, regardless of its level of socio-economic development. &#x0D; The underground economy refers to economic transactions that are deemed illegal, either because the goods or services traded are unlawful in nature, or because transactions fail to comply with governmental reporting requirements.&#x0D; Also called the underground, informal, or parallel economy, the shadow economy includes not only illegal activities but also unreported income from the production of legal goods and services, either from monetary or barter transactions. Hence, the shadow economy comprises all economic activities that would generally be taxable were they reported to the tax authorities.&#x0D; A precise definition of the shadow economy, however, is quite difficult because the shadow economy develops all the time, adjusting to changes in taxation and regulations.&#x0D; Shadow economy is a complex phenomenon that has become significant in Ukraine. This phenomenon in Ukraine is one of the main barriers to European integration, increasing competitiveness in the world market, improving living standards within the country. The presence of a shadow economy indicates the activity of illegal economic activity in the country, a high level of corruption in the public sector, a low level of legal and tax morality in society. Ukraine still has a significant volume shadow economy, which significantly impairs the socio-economic development of the state. Shadow economy has become one of the most acute economic and socio-political problems in Ukraine and poses a threat to the economic and national security of the state. &#x0D; The shadow economy is present unevenly in different sectors of the economy. Determining the level of the shadow economy allows the government to identify which sectors have to be given priority.&#x0D; The work based on the analysis of a significant array of analytical and statistical material. The problem of a significant level of shadowing of the economy in Ukraine is considered. The article describes the method of calculating the level of the shadow economy and compares the levels of the shadow economy in Ukraine from 2010 to 2020.&#x0D; Authors study the causes and consequences of shadowing a country's economy and describe possible ways to overcome the negative phenomenon.

Addressing Crypto-Ransomware Attacks: Before You Decide whether To-Pay or Not-To

ABSTRACT Crypto-ransomware attacks have forced victims to part away with millions of dollars using various intimidation and scare tactics. Victims have made hasty decisions of whether to pay or not without adequate information. In this paper, we explore options to address ransomware attacks before considering whether to pay or not. We propose a ransomware categorization framework that classifies the virulence of a ransomware attack using a proposed classification algorithm that is based on data deletion and file encryption attack structures. The categories that increase in severity from CAT1 to CAT8 classify the technical prowess and the overall effectiveness of potential ways of retaining the data without paying the ransom demand. The framework provides an avenue for a deeper comprehension of potential inadequacies and flaws to be exploited for data recovery. Results show that poorly implemented attack structures make recovery of data possible via system volume shadow copies or third-party software without paying.

Simulating Shadow Interactions for Outdoor Augmented Reality With RGBD Data

In augmented reality, interactive shadow casting between virtual and real objects is crucial for the consistency of the appearance of integrated scenes. Since real shadow-casting objects may not be fully visible in live videos, simulating the shadows that they cast onto virtual objects based on 3D reconstruction will fail. To address this issue, we propose a framework for simulating shadow interactions in live outdoor videos based on shadow edges. The simulation framework consists of two components: real-time casting shadow detection from live videos with moving viewpoints and generation of shadow volumes. First, we propose a novel split-based shadow detection framework that accounts for moving viewpoints. Then, a visual-perception-guided adaptive sampling strategy is developed to generate high-quality shadow volumes. The experimental results demonstrate that our algorithm achieves visually consistent shadow interactions for live outdoor videos, which significantly enhances the photorealism of the generated scenes for augmented reality (AR) applications.

Detection of Timestamps Tampering in NTFS using Machine Learning

During a digital investigation, the recorded time of activity on the system is crucial for solving the case. But file times may be subject to user manipulation for deceptive reasons. Detecting such timestamps change, in a none-automatic way, will come to finding a needle in a haystack. Many ways can lead to timestamps manipulation: the presence of anti-forensics tools, unusual timestamp differences in the volume shadow copies, the system restore points and the filesystem metadata, inconsistencies in the filesystem timestamps or with the established rules of normal time behavior, timeline analysis, etc. However, while reviewing the literature, we found little use of the capabilities of machine learning algorithms in such detection. In this paper, a machine learning approach for the automatic detection of timestamps tampering is proposed to reduce the required manual search for such manipulation. Put differently, the approach predicts a classification of input files in whether they have been timestamp tampered or not. Furthermore, the process of a synthetic dataset collection, features engineering and extraction, dataset manipulation, training, and model evaluation is presented. To recapitulate, the held experiment generates the synthetic dataset from a virtual controlled environment, apply a machine learning algorithm on a subset of the dataset, predict on the other subset of the dataset and present the results using confusion matrix, receiver operating characteristic curves, precision-recall curves, accuracy, and log_loss.

Mitigating the effects of boom occlusion on automated aerial refueling through shadow volumes

In-flight refueling of unmanned aerial vehicles (UAVs) is critical to the United States Air Force (USAF). However, the large communication latency between a ground-based operator and his/her remote UAV makes docking with a refueling tanker unsafe. This latency may be mitigated by leveraging a tanker-centric stereo vision system. The vision system observes and computes an approaching receiver’s relative position and orientation offering a low-latency, high frequency docking solution. Unfortunately, the boom – an articulated refueling arm responsible for physically pumping fuel into the receiver – occludes large portions of the receiver especially as the receiver approaches and docks with the tanker. The vision system must be able to compensate for the boom’s occlusion of the receiver aircraft. We present a novel algorithm for mitigating the negative effects of boom occlusion in stereo-based aerial environments. Our algorithm dynamically compensates for occluded receiver geometry by transforming the occluded areas into shadow volumes. These shadow volumes are then used to cull hidden geometry that is traditionally consumed, in error, by the vision processing and point registration pipeline. Our algorithm improves computer-vision pose estimates by 44% over a naïve approach without shadow volume culling.

ReLiShaft: realistic real-time light shaft generation taking sky illumination into account

Rendering atmospheric phenomena is known to have its basis in the fields of atmospheric optics and meteorology and is increasingly used in games and movies. Although many researchers have focused on generating and enhancing realistic light shafts, there is still room for improvement in terms of both qualification and quantification. In this paper, a new technique, called ReLiShaft, is presented to generate realistic light shafts for outdoor rendering. In the first step, a realistic light shaft with respect to the sun position and sky colour in any specific location, date and time is constructed in real-time. Then, Hemicube visibility-test radiosity is employed to reveal the effect of a generated sky colour on environments. Two different methods are considered for indoor and outdoor rendering, ray marching based on epipolar sampling for indoor environments, and filtering on regular epipolar of z-partitioning for outdoor environments. Shadow maps and shadow volumes are integrated to consider the computational costs. Through this technique, the light shaft colour is adjusted according to the sky colour in any specific location, date and time. The results show different light shaft colours in different times of day in real-time.

Deformation Factors of the Entrepreneurship Development in the Industry Segments of the Economy of the Russian Federation

The article identifies the reasons for deformation of small business in the timber sector of the economy in the cross-section of three groups - social, ecological and economical (lack of financial resources, imperfect government regulation; high tax burden).The evidence for such factors is seen in the increase of shadow volumes of timber flow, decrease in the quality and volumes of forest recreating activities and forest protection, decrease in tax revenues and payments, decrease in business and innovation activity in the sector. Stable business performance in the wood sector depends on the economic, ecological and social factors.It is proven, that decreases in the scale of business deformation in the timber sector is possible, via forming a differentiated government policy to support entrepreneurship and organizational-economical tools.

In-Class Exercises for Shadow Volume Algorithms

This article describes a simple course exercise to deepen the understanding of real-time shadow volume algorithms. The exercise takes less than 10 minutes to perform during lecture time, leads to a profounder understanding of the topic, and serves as a basis for further discussions of improvements for the shadow mapping algorithm. Using this exercise, the authors noticed an increase in students implementing shadow algorithms for later real-time graphics projects.

Partitioned Shadow Volumes

AbstractReal‐time shadows remain a challenging problem in computer graphics. In this context, shadow algorithms generally rely either on shadow mapping or shadow volumes. This paper rediscovers an old class of algorithms that build a binary space partition over the shadow volumes. For almost 20 years, such methods have received little attention as they have been considered lacking of both robustness and efficiency. We show that these issues can be overcome, leading to a simple and robust shadow algorithm. Hence we demonstrate that this kind of approach can reach a high level of performance. Our algorithm uses a new partitioning strategy which avoids any polygon clipping. It relies on a Ternary Object Partitioning tree, a new data structure used to find if an image point is shadowed. Our method works on a triangle soup and its memory footprint is fixed. Our experiments show that it is efficient and robust, including for finely tessellated models.

Methods of Isolation for Application Traces Using Virtual Machines and Shadow Copies

To improve the user's experience, almost all applications save usage data: web browsers save history and cookies, chat programs save message archives and so on. However, this data can be confidential and may compromise the user's privacy. There are third party solutions to automatically detect and wipe these traces, but they have two problems: they need a constantly updated database of files to target, and they wipe the data after it has been written to the disk. Our proposed solution does not need a database and it automatically reverts the application to its initial (clean) state, leaving no traces behind. This is done by using a monitoring process developed by us and the Volume Shadow Copy Service that takes snapshots when the application runs and restores them at the end of the run. Keywords—security; privacy; application traces; data wiping;

Adaptive sampling approach for volumetric shadows in dynamic scenes

Ray marching is an important technique to generate volumetric lighting effects. However, it is very expensive for each pixel on the screen, especially in dynamic scenes. The authors propose an adaptive approach to reduce samples for volumetric shadows in the time domain. In dynamic scenes, shadow volumes of moving objects are created and are rasterised to decide pixels that cannot be reused. The authors use a stencil buffer to maintain the information of screen pixels by recomputing or just using the previous information. Experimental results show that the proposed approach is simple to implement. Moreover, compared to the previous method, the proposed approach achieves a specific speedup and maintains similar visual quality.

Accurate Shadow Modeling Algorithm for Simulation of Fringe Projection System

We present some new idea to implement shadow modeling which is an important process for simulation of fringe projection system: The dot product between normal vector of object’s surface and vector that connecting projector lens centre and point on object’s surface, and the dot product between normal vector of object’s surface and vector that connecting camera lens centre and point on object’s surface are used to model the shadow on object’s surface. Our algorithm do not need to implement the calculation of the silhouettes of the occluders. Simulation result validates that the accuracy of our shadow modeling algorithm is same as shadow volumes algorithm, but our algorithm runs faster than shadow volumes algorithm.

The Value of Measuring Food Availability on the Ground for a Semiterrestrial Frugivore, the Tana River Mangabey (Cercocebus galeritus) of Kenya

Collecting phenological data, seasonal availability of plant resources that primates feed on, allows us to understand feeding ecology better. A number of primates are terrestrial or semiterrestrial frugivores, yet phenology is generally measured only in the canopy. I hypothesized that combining measurements of food availability on the ground with canopy measurements would more strongly correlate with diet than canopy measurements alone for a semiterrestrial frugivore, the Tana River mangabey (Cercocebus galeritus). From July 2005 until June 2006, I conducted monthly follows on a mangabey group. Phenology was measured in 105 individuals of their top seven food tree species. I measured canopy phenology on a 0–5 scale and counted fruits in three 1 m3 areas of the canopy, and measured ground phenology by counting fruits and seeds in four 1 m2 quadrats under the canopy. I calculated each tree’s canopy volume and canopy shadow, and each species’ mean fruit weight, mean seed weight, and density. Monthly biomasses were calculated as kilograms per hectare. Spearman correlations were performed between diet contribution and canopy biomass, ground biomass, and total biomass. The hypothesis was not supported for seven species individually or combined. The hypothesis was supported for 3 of 12 diet items, although canopy biomass was also significant for 2 of those items. Two diet items correlated only with ground biomass. Studies of the Tana River mangabey may benefit from measuring ground phenology only for those items eaten exclusively on the ground. Primatologists studying terrestrial or semiterrestrial frugivores should consider feeding height when deciding on phenology methods.

A sweep and translate algorithm for computing voxelized 3D Minkowski sums on the GPU

Computing the Minkowski sum of two arbitrary polyhedra in R3 is difficult because of high combinatorial complexity. We present an algorithm for directly computing a voxelization of the Minkowski sum of two closed watertight input polyhedra for applications such as path planning that do not require a boundary representation as output. We introduce a new decomposition formula for computing the Minkowski sum and prove its correctness. We describe an efficient Graphics Processing Unit (GPU) implementation of the algorithm using stencil shadow volumes to create a solid voxelization of the Minkowski sum.