Reversible Jump Metropolis Light Transport using Inverse Mappings

We study Markov Chain Monte Carlo (MCMC) methods operating in primary sample space and their interactions with multiple sampling techniques. We observe that incorporating the sampling technique into the state of the Markov Chain, as done in Multiplexed Metropolis Light Transport (MMLT), impedes the ability of the chain to properly explore the path space, as transitions between sampling techniques lead to disruptive alterations of path samples. To address this issue, we reformulate Multiplexed MLT in the Reversible Jump MCMC framework (RJMCMC) and introduce inverse sampling techniques that turn light paths into the random numbers that would produce them. This allows us to formulate a novel perturbation that can locally transition between sampling techniques without changing the geometry of the path, and we derive the correct acceptance probability using RJMCMC. We investigate how to generalize this concept to non-invertible sampling techniques commonly found in practice, and introduce probabilistic inverses that extend our perturbation to cover most sampling methods found in light transport simulations. Our theory reconciles the inverses with RJMCMC yielding an unbiased algorithm, which we call Reversible Jump MLT (RJMLT). We verify the correctness of our implementation in canonical and practical scenarios and demonstrate improved temporal coherence, decrease in structured artifacts, and faster convergence on a wide variety of scenes

Wpływ nasilenia lęku jako cechy na siłę mięśni pacjentów poddanych operacyjnej rekonstrukcji więzadła krzyżowego przedniego stawu kolanowego

Założenia: Izolowane zerwanie więzadła krzyżowego przedniego kolana ACL jest trzecim co do częstości urazem więzadłowym stawu kolanowego. Postępowanie obejmuje rekonstrukcję i rehabilitację pooperacyjną. Wyniki leczenia ocenia się m.in. na podstawie testów ortopedycznych, badań siły mięśniowej i pomiarów obwodów, porównywanych do nogi przeciwnej. Stan kliniczny operowanego więzadła nie zawsze jest zbieżny z odczuciami pacjenta co do własnego zdrowia. Wpływ na samoocenę zdrowia przez pacjenta i przebieg rehabilitacji ma między innymi nasilenie lęku. Cel: Ocena wpływu predyspozycji do reagowania lękiem na skuteczność rehabilitacji, ocenianej w oparciu o pomiary siły mięśni, po operacyjnym leczeniu przerwanego więzadła krzyżowego przedniego kolana. Materiał i metoda: Badano 201 pacjentów z rozpoznanym zerwaniem więzadła krzyżowego przedniego kolana (113 kobiet i 88 mężczyzn). Wszyscy pacjenci zostali poddani rekonstrukcji więzadła krzyżowego przedniego oraz sześciomiesięcznemu leczeniu rehabilitacyjnemu. Do oceny nasilenia lęku jako cechy badanego przed zabiegiem operacyjnym zastosowano Kwestionariusz STAI, a do dwukrotnego badania siły mięśni (tydzień przed i po 6 miesiącach od operacji) zastosowano dynamometr. Wyniki: Badani wykazujący małe nasilenie lęku-cechy (poniżej 3,5 stena) istotnie częściej niż badani wykazujący duże nasilenie lęku-cechy (powyżej 7,5 stena) uzyskiwali po rehabilitacji zwiększenie siły mięśni przywodzicieli stawu biodrowego i prostowników stawu kolanowego, oraz poprawę w teście leg press operowanej kończyny dolnej. Wnioski: Zwiększona predyspozycja do reagowania lękiem może być przyczyną gorszych wyników rehabilitacji pacjentów po operacyjnej rekonstrukcji więzadła krzyżowego przedniego. W przypadku pacjentów o nasilonym lęku, rehabilitowanych po operacyjnej rekonstrukcji więzadła krzyżowego przedniego, należy rozważyć zastosowanie indywidualnego programu rehabilitacji, uwzględniającego psychoterapię.Background: The rupture of the anterior cruciate ligament (ACL) constitutes the third most frequent ligament injury of the knee joint. The approach involves its reconstruction and post-operational rehabilitation. The results of treatment are evaluated on the basis of, among other things, orthopaedic tests, tests of muscle strength and circumference measurements when compared to the other leg. The clinical state of the ligament is not always in accordance with the patient’s perceptions as to their state of health. An influence on the self evaluation of health on the part of the patient is brought about by, among other things, an intensification in fear and anxiety. Objective: An evaluation of the influence of a predisposition for an anxiety reaction on the effectiveness of rehabilitation, evaluated in relation to the measurement of muscle strength, following operational treatment of the injured ACL. Materials and Methods: 201 patients (113 women and 88 men) were tested who had a diagnosed of the ACL injury. All the patients were subjected to a reconstruction of the ACL as well as a period of six months of rehabilitation treatment. The STAI questionnaire was used in the evaluation of the trait-anxiety prior to the operational procedure, while twice a dynamometer was used in the testing of muscle strength (a week before and six months after the operation). Results: Those patients displaying a small intensification in trait-anxiety (lower than 3.5) significantly more often than those patients displaying a large intensification in trait-anxiety (over 7.5) gained increased muscle strength following rehabilitation of the hip joint adductor and the extensors of the knee joint, as well as an improvement in the leg press test of the lower limb operated on. Conclusions: An increased predisposition for an anxiety reaction may be the reason for poorer rehabilitation results in patients following an operational reconstruction of the ACL. It may be necessary in the case of patients undergoing rehabilitation after an operational reconstruction of the ACL and who display an intensive anxiety of the said to consider the application of an individual programme of rehabilitation, one incorporating elements of psychotherapy

Real-Time Volumetric Shadows using 1D Min-Max Mipmaps

Light scattering in a participating medium is responsible for several important effects we see in the natural world. In the presence of occluders, computing single scattering requires integrating the illumination scattered towards the eye along the camera ray, modulated by the visibility towards the light at each point. Unfortunately, incorporating volumetric shadows into this integral, while maintaining real-time performance, remains challenging. In this paper we present a new real-time algorithm for computing volumetric shadows in single-scattering media on the GPU. This computation requires evaluating the scattering integral over the intersections of camera rays with the shadow map, expressed as a 2D height field. We observe that by applying epipolar rectification to the shadow map, each camera ray only travels through a single row of the shadow map (an epipolar slice), which allows us to find the visible segments by considering only 1D height fields. At the core of our algorithm is the use of an acceleration structure (a 1D minmax mipmap) which allows us to quickly find the lit segments for all pixels in an epipolar slice in parallel. The simplicity of this data structure and its traversal allows for efficient implementation using only pixel shaders on the GPU

Second-order Occlusion-aware Volumetric Radiance Caching

Accurate simulation of light transport in participating media is expensive, due to the many sca ering events. However, the band- limiting e ect of sca ering in media makes this kind of light trans- port very suitable for adaptive sampling and reconstruction tech- niques. In this work we present a novel algorithm that adaptively samples radiance from sparse points in the medium using up-to second-order occlusion-aware derivatives to determine when in- terpolation is appropriate. We derive our metric from each point’s incoming light eld. We use a proxy triangulation-based repre- sentation of the radiance re ected by the surrounding medium and geometry to e ciently compute the rst- and second-order derivatives of the radiance at the cache points while accounting for occlusion changes. We validate the quality of our approach on a self-contained two-dimensional model for light transport in media. en we show how our results generalize to practical three- dimensional scenarios, where we show much be er results while reducing computation time up to a 30% compared to previous work

Second-Order Occlusion-Aware Volumetric Radiance Caching

We present a second-order gradient analysis of light transport in participating media and use this to develop an improved radiance caching algorithm for volumetric light transport. We adaptively sample and interpolate radiance from sparse points in the medium using a second-order Hessian-based error metric to determine when interpolation is appropriate. We derive our metric from each point's incoming light field, computed by using a proxy triangulation-based representation of the radiance reflected by the surrounding medium and geometry. We use this representation to efficiently compute the first- and second-order derivatives of the radiance at the cache points while accounting for occlusion changes. We also propose a self-contained two-dimensional model for light transport in media and use it to validate and analyze our approach, demonstrating that our method outperforms previous radiance caching algorithms both in terms of accurate derivative estimates and final radiance extrapolation. We generalize these findings to practical three-dimensional scenarios, where we show improved results while reducing computation time by up to 30\% compared to previous work

Ocena częstości występowania zespołu Wolframa w populacji dzieci z cukrzycą

Introduction: Wolfram syndrome (WFS) is the most frequent syndromic form of monogenic diabetes coexisting with optic atrophy and many other disorders. The aim of this study was to estimate the prevalence of Wolfram syndrome among children with diabetes in Poland.Material and methods: These calculations were performed among Polish diabetic children, aged 0–18 years, from three administrative regions between January 2005 and December 2011. Epidemiological data was obtained by matching the results from the EURO-WABBPoland Project and the PolPeDiab Registry.Results: Throughout the study period, we confirmed genetic diagnosis of Wolfram syndrome in 13 patients from Poland. Three patients originated from the studied regions with complete epidemiological data on paediatric diabetes. The total number of patients with diagnosed diabetes in the study equalled 2,568 cases. The prevalence of Wolfram syndrome among Polish children with diabetes is 0.12% (95% Confidence Interval 0.04–0.34%).Conclusions: We estimate that Wolfram syndrome is 26 to 35 times less frequent than monogenic diabetes (MODY and neonatal diabetes) in the Polish paediatric population. (Endokrynol Pol 2014; 65 (4): 295–297)Wstęp: Zespół Wolframa (WFS) jest najczęstszą syndromiczną formą cukrzycy monogenowej, gdzie oprócz cukrzycy występuje zanik nerwów wzrokowych oraz wiele innych zaburzeń. Celem pracy była ocena częstości występowania zespołu Wolframa na tle innych rodzajów cukrzycy w populacji pediatrycznej.Materiał i metody: Ocena chorobowości została przeprowadzona wśród dzieci chorych na cukrzycę, pochodzących z trzech polskich województw (łódzkie, pomorskie i śląskie) w wieku 0–18 lat, w okresie czasu pomiędzy styczniem 2005 roku i grudniem 2011. Dane epidemiologiczne uzyskano poprzez połączenie danych pochodzących z Rejestru EURO-WABB dla Polski oraz Rejestru PolPeDiab.Wyniki: W badanym okresie czasu potwierdzono genetycznie rozpoznanie zespołu Wolframa u 13 pacjentów na terenie Polski. Do niniejszej analizy włączono 3 pacjentów z zespołem Wolframa pochodzących z badanego regionu. Całkowita liczba przypadków cukrzycy zdiagnozowanych w tym okresie czasu wyniosła 2568. Prewalencję zespołu Wolframa wśród pacjentów pediatrycznych z cukrzycą oszacowano na 0.12% (95% Przedział Ufności 0.04–0.34%).Wnioski: Oceniono, że zespół Wolframa występuje w polskiej populacji pediatrycznej 26- do 35-krotnie rzadziej niż pozostałe typy cukrzycy monogenowej (MODY i cukrzyca noworodkowa). (Endokrynol Pol 2014; 65 (4): 295–297

Electrochemical oxidation of Ti15Mo alloy : the impact of anodization parameters on surface morphology of nanostructured oxide layers

It is well-known that the structure and composition of the material plays an important role in the processes occurring at the surface. In this paper, a surface morphology of nanostructured oxide layers electrochemically grown on Ti15Mo, tuned by applying different anodization parameters, was investigated in detail. The one-step anodization of Ti15Mo alloy was performed at room temperature in an ethylene glycol-based electrolyte containing 0.11 M NH4F and 1.11 M H2O. Different anodization times (ranging from 5 to 60 min) and applied potentials (40–100 V) were tested, and the surface morphology, elemental content, and crystalline structure were monitored by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffractometry (XRD), respectively. The results showed that contrary to the multistep anodization of titanium foil, the surface morphology of anodic oxide obtained via the one-step process contains the nanoporous outer layer covering the nanotubular structure. What is more, the pore diameter (Dp) and interpore distance (Dint) of such layers exhibit different trends than those observed for anodization of pure titanium. In particular, at a certain potential range, a decrease in both Dp and Dint with increasing potential was observed. However, independently on the used anodization conditions, the elemental content of oxide layers remained similar, showing the amount of molybdenum at c.a. 15 wt.%. Finally, the amorphous nature of as-anodized layers was confirmed, and their optical band-gap was determined from the diffuse reflectance UV–Vis spectra. It was found that Eg is tunable to some extent by changing the anodizing potential. However, further thermal treatment in air at 400 °C resulted in the anatase phase formation that was accompanied by a significant Eg reduction. Therefore, we believe that the presented results will greatly contribute to the understanding of anodic formation of nanostructured functional oxide layers with tunable properties that can be applied in various fields

A radiative transfer framework for non-exponential media

We develop a new theory of volumetric light transport for media with non-exponential free-flight distributions. Recent insights from atmospheric sciences and neutron transport demonstrate that such distributions arise in the presence of correlated scatterers, which are naturally produced by processes such as cloud condensation and fractal-pattern formation. Our theory accommodates correlations by disentangling the concepts of the free-flight distribution and transmittance, which are equivalent when scatterers are statistically independent, but become distinct when correlations are present. Our theory results in a generalized path integral which allows us to handle non-exponential media using the full range of Monte Carlo rendering algorithms while enriching the range of achievable appearance. We propose parametric models for controlling the statistical correlations by leveraging work on stochastic processes, and we develop a method to combine such unresolved correlations (and the resulting non-exponential free-flight behavior) with explicitly modeled macroscopic heterogeneity. This provides a powerful authoring approach where artists can freely design the shape of the attenuation profile separately from the macroscopic heterogeneous density, while our theory provides a physically consistent interpretation in terms of a path space integral. We address important considerations for graphics including energy conservation, reciprocity, and bidirectional rendering algorithms, all in the presence of surfaces and correlated media

An augmented reality sign-reading assistant for users with reduced vision

People typically rely heavily on visual information when finding their way to unfamiliar locations. For individuals with reduced vision, there are a variety of navigational tools available to assist with this task if needed. However, for wayfinding in unfamiliar indoor environments the applicability of existing tools is limited. One potential approach to assist with this task is to enhance visual information about the location and content of existing signage in the environment. With this aim, we developed a prototype software application, which runs on a consumer head-mounted augmented reality (AR) device, to assist visually impaired users with sign-reading. The sign-reading assistant identifies real-world text (e.g., signs and room numbers) on command, highlights the text location, converts it to high contrast AR lettering, and optionally reads the content aloud via text-to-speech. We assessed the usability of this application in a behavioral experiment. Participants with simulated visual impairment were asked to locate a particular office within a hallway, either with or without AR assistance (referred to as the AR group and control group, respectively). Subjective assessments indicated that participants in the AR group found the application helpful for this task, and an analysis of walking paths indicated that these participants took more direct routes compared to the control group. However, participants in the AR group also walked more slowly and took more time to complete the task than the control group. The results point to several specific future goals for usability and system performance in AR-based assistive tools.Peer reviewed: YesNRC publication: Ye