A hallmark capability that defines a renderer as a production renderer is the ability to scale to handle scenes with extreme complexity, including complex illumination cast by a vast number of light sources. In this paper, we present Cache Points, the system used by Disney’s Hyperion Renderer to perform efficient unbiased importance sampling of direct illumination in scenes containing up to millions of light sources. Our cache points system includes a number of novel features. We build a spatial data structure over points that light sampling will occur from instead of over the lights themselves. We do online learning of occlusion and factor this into our importance sampling distribution. We also accelerate sampling in difficult volume scattering cases. Over the past decade, our cache points system has seen extensive production usage on every CG feature film and animated short produced by Walt Disney Animation Studios, enabling artists to design lighting environments without concern for complexity. In this paper, we will survey how the cache points system is built, works, impacts production lighting and artist workflows, and factors into the future of production rendering at Disney Animation.

We present a novel algorithm to denoise deep Monte Carlo renderings, in which pixels contain multiple colour values, each for a different range of depths. Deep images are a more expressive representation of the scene than conventional flat images. However, since each depth bin receives only a fraction of the flat pixel's samples, denoising the bins is harder due to the less accurate mean and variance estimates. Furthermore, deep images lack a regular structure in depth—the number of depth bins and their depth ranges vary across pixels. This prevents a straightforward application of patch‐based distance metrics frequently used to improve the robustness of existing denoising filters. We address these constraints by combining a flat image‐space non‐local means filter operating on pixel colours with a deep cross‐bilateral filter operating on auxiliary features (albedo, normal, etc.). Our approach significantly reduces noise in deep images while preserving their structure. To our best knowledge, our algorithm is the first to enable efficient deep‐compositing workflows with denoised Monte Carlo renderings. We demonstrate the performance of our filter on a range of scenes highlighting the challenges and advantages of denoising deep images.

BACKGROUND:In patients with Chiari I malformation (CMI), the occurrence of acute neurologic deficit after craniocervical trauma is rare. However, the pathologic potential of exacerbating anatomic overcrowding of the posterior fossa has immense clinical consequences and prompt recognition is essential.CASE DESCRIPTION:This case study describes a 41-year-old male who sustained a single blow to the face, fell, and struck the occiput. On admission, neurological examination revealed a profound paraparesis, upper extremity diplegia, a C4 sensory level and apnea that required intubation. On arrival, computerized axial tomography of the head showed a small amount of contrecoup left frontal traumatic subarachnoid hemorrhage. Magnetic resonance imaging (MRI) performed 19 h after admission was negative except for the presence of a CMI. He acutely declined on post injury day 2, prompting emergent decompression of the posterior fossa where anatomic overcrowding was observed. At 19 weeks post injury, his motor function had significantly improved.CONCLUSION:The constellation of severe neurologic deficit in patients with CMI after relatively minor craniocervical trauma has been previously described. In our patient, neurologic deficit disproportionate to the mechanism of injury was observed and likely in part attributed to the presence of a Chiari malformation. Unfortunately, MRI has not yet been able to clearly define the underlying pathoanatomy, help understand the mechanism of injury, and delineate when operative intervention is indicated in these patients. Here, we review similar cases from the literature, examine findings on MRI, and evaluate mechanisms of injury following craniocervical trauma in patients with CMI to help clarify these questions.

The actuation strain of an equibiaxially prestrained dielectric elastomer membrane is studied as a function of driving frequency and prestrain. Experimental data are gathered on the membrane's creep and recovery following DC actuation, as well as the steady state amplitude and phase for AC driving voltages ranging from 2 to 40 Hz. The effect of prestretch on steady state actuation was also investigated, using membranes of both 250% and 300% prestretch. A three-element generalized Kelvin-Voigt model is developed to capture the transient and steady-state actuation responses as a function of frequency and prestrain. We show that, despite its relative simplicity, this model captures the relevant timescales for the membrane behavior with good fidelity and can be used to accurately predict the actuation magnitude and phase as a function of time over a range of actuation configurations and driving conditions.

We address the problem of denoising Monte Carlo renderings by studying existing approaches and proposing a new algorithm that yields state-of-the-art performance on a wide range of scenes. We analyze existing approaches from a theoretical and empirical point of view, relating the strengths and limitations of their corresponding components with an emphasis on production requirements. The observations of our analysis instruct the design of our new filter that offers high-quality results and stable performance. A key observation of our analysis is that using auxiliary buffers (normal, albedo, etc.) to compute the regression weights greatly improves the robustness of zero-order models, but can be detrimental to first-order models. Consequently, our filter performs a first-order regression leveraging a rich set of auxiliary buffers only when fitting the data, and, unlike recent works, considers the pixel color alone when computing the regression weights. We further improve the quality of our output by using a collaborative denoising scheme. Lastly, we introduce a general mean squared error estimator, which can handle the collaborative nature of our filter and its nonlinear weights, to automatically set the bandwidth of our regression kernel.

Renderings of animation sequences with physics-based Monte Carlo light transport simulations are exceedingly costly to generate frame-by-frame, yet much of this computation is highly redundant due to the strong coherence in space, time and among samples. A promising approach pursued in prior work entails subsampling the sequence in space, time, and number of samples, followed by image-based spatio-temporal upsampling and denoising. These methods can provide significant performance gains, though major issues remain: firstly, in a multiple scattering simulation, the final pixel color is the composite of many different light transport phenomena, and this conflicting information causes artifacts in image-based methods. Secondly, motion vectors are needed to establish correspondence between the pixels in different frames, but it is unclear how to obtain them for most kinds of light paths (e.g. an object seen through a curved glass panel). To reduce these ambiguities, we propose a general decomposition framework, where the final pixel color is separated into components corresponding to disjoint subsets of the space of light paths. Each component is accompanied by motion vectors and other auxiliary features such as reflectance and surface normals. The motion vectors of specular paths are computed using a temporal extension of manifold exploration and the remaining components use a specialized variant of optical flow. Our experiments show that this decomposition leads to significant improvements in three image-based applications: denoising, spatial upsampling, and temporal interpolation.

We define our decomposition using Heckbert’s [Hec90] light path notation to classify light paths or families of similar light paths. We label the first vertex on the camera sensor E (“eye”), and denote the subsequent scattering vertices based on a classification of the underlying materials. We use the following notation: (D) diffuse, (R) specular (or glossy) reflection, (T) specular (or glossy) transmission We classify glossy light interactions (e.g. scattering off rough metal or glass) as R or T if the roughness is below a threshold (Beckmann roughness α < 0.1 in our experiments), otherwise we consider them to be diffuse D.

BACKGROUND:Cerebral microdialysis (MD) provides valuable information about brain metabolism under normal and pathologic conditions. The CMA 600 microdialysis analyzer received US Food and Drug Administration (FDA) approval for clinical use in the United States in 2005. Since then, cerebral MD has been increasingly utilized nationally in the multimodal monitoring of traumatic brain injury (TBI), stroke, aneurysmal subarachnoid hemorrhage, and brain tumors. We describe a 5-year, single-institutional experience using cerebral MD at a community-based hospital, Legacy Emanuel Medical Center (LEMC). Implications for the adoption and utility of MD in medical centers with limited resources are discussed.METHODS:This is a retrospective chart review and data analysis of 174 consecutive patients who had cerebral MD as part of multimodal brain monitoring. All cerebral MD catheters were placed by board-certified, attending neurosurgeons at LEMC. Clinical severity in the TBI patients was reported using initial Glasgow Coma Scale (GCS); radiologic severity was graded with the Marshall CT grading scale. Measures of the risks of MD placement included post-placement hemorrhage, cerebral infection, and dislodgement.RESULTS:Between July 2005 and July 2010, 248 cerebral MD catheters were placed in 174 patients undergoing multimodal brain monitoring. One hundred and eighty-five catheters were placed at the time of open craniotomy. None were associated with cranial infection. Patients ranged in age from 5 months to 90 years, with a mean of 49 years. The male to female ratio was 1.4:1. The underlying pathologies were: TBI (126), cerebral vascular accident (24), aneurysmal subarachnoid hemorrhage (17), and tumor (7).CONCLUSIONS:Cerebral MD was readily implemented in a community-based hospital. No cerebral hemorrhages or infections were attributed to cerebral MD. Examples of how MD may be a useful adjunct in the clinical decision making of patients with brain injuries are presented.

Personal use only. For copyright permission information: Published online http://www.cconline.org © 2011 American Association of Critical-Care Nurses doi: 10.4037/ccn2010226 2011;31:25-37 Crit Care Nurse Jefferson W. Chen Sandy Cecil, Patrick M. Chen, Sarah E. Callaway, Susan M. Rowland, David E. Adler and Theory to Clinical Practice Traumatic Brain Injury : Advanced Multimodal Neuromonitoring From

Thank you for your question. Normal ICP measurements can range from 0 to 15 mm Hg,1with critical values greater than 20 mm Hg. Normal CPP range is 60 to 100 mm Hg.1Our neuro-surgeon’s practice is to allow permissive CPP ranges of 50 to 60 mm Hg, depending on the patient’s pathology.In regard to hyperventilation, we use very “brief” trials of hyperventilation as a temporary measure in order to decrease ICP if it is dangerously elevated. We agree, this is not a common practice of late, but it is still (on rare occasions) used while monitoring patients. We support a PaCO2range of 35 to 40 mm Hg. We listed several references that supported the options we presented in the article.

I read “Traumatic Brain Injury: Advanced Multimodal Neuromonitoring From Theory to Clinical Practice” (April 2011:25–37) and found a few items that may need further clarification. On page 30, the authors state that baseline “normal ICP [intracranial pressure] levels range from 0 to 10 mm Hg.” According to Campbell,1(p600) normal ICP values can range from 5 to 15 mm Hg. In addition, Wiegand2(p802) and Carlson3(p554) state normal ICP is 5 to 15 mm Hg.In the same paragraph on page 30, the authors state that ideal cerebral perfusion pressure (CPP) is approximately 60 mm Hg. Although 60 mm Hg reflects the old range, the new range is between “50 and 70 mm Hg.”2(p803) Carlson3(p554) writes that the normal value is 60 to 100 mm Hg. Consequently, the ideal range for CPP has increased.The authors state that a first-tier intervention to reduce ICP is to increase the PaCO2. I believe this needs to be clarified so practitioners realize that we do not hyperventilate patients as we did in the past; rather we maintain a “controlled hyperventilation” with a goal of maintaining PaCO2 in the low end of normal, that is, 35 to 40 mm Hg.3(p561)

Traumatic brain injury accounts for nearly 1.4 million injuries and 52 000 deaths annually in the United States. Intensive bedside neuromonitoring is critical in pre- venting secondary ischemic and hypoxic injury common to patients with traumatic brain injury in the days following trauma. Advancements in multimodal neuromon- itoring have allowed the evaluation of changes in markers of brain metabolism (eg, glucose, lactate, pyruvate, and glycerol) and other physiological parameters such as intracranial pressure, cerebral perfusion pressure, cerebral blood flow, partial pressure of oxygen in brain tissue, blood pressure, and brain temperature. This article high- lights the use of multimodal monitoring in the intensive care unit at a level I trauma center in the Pacific Northwest. The trends in and significance of metabolic, physio- logical, and hemodynamic factors in traumatic brain injury are reviewed, the tech- nical aspects of the specific equipment used to monitor these parameters are described, and how multimodal monitoring may guide therapy is demonstrated. As a clinical practice, multimodal neuromonitoring shows great promise in improving bedside therapy in patients with traumatic brain injury, ultimately leading to improved neurological outcomes. (Critical Care Nurse. 2011;31:25-37)

Traumatic brain injury accounts for nearly 1.4 million injuries and 52 000 deaths annually in the United States. Intensive bedside neuromonitoring is critical in preventing secondary ischemic and hypoxic injury common to patients with traumatic brain injury in the days following trauma. Advancements in multimodal neuromonitoring have allowed the evaluation of changes in markers of brain metabolism (eg, glucose, lactate, pyruvate, and glycerol) and other physiological parameters such as intracranial pressure, cerebral perfusion pressure, cerebral blood flow, partial pressure of oxygen in brain tissue, blood pressure, and brain temperature. This article highlights the use of multimodal monitoring in the intensive care unit at a level I trauma center in the Pacific Northwest. The trends in and significance of metabolic, physiological, and hemodynamic factors in traumatic brain injury are reviewed, the technical aspects of the specific equipment used to monitor these parameters are described, and how multimodal monitoring may guide therapy is demonstrated. As a clinical practice, multimodal neuromonitoring shows great promise in improving bedside therapy in patients with traumatic brain injury, ultimately leading to improved neurological outcomes.

Novel electron-optical components and concepts aiming at improving the throughput and extending the applications of a low energy electron microscope (LEEM) are elucidated: an immersion magnetic field in the objective lens and its implications for the illumination optics, a dual electron beam illumination approach, and imaging modes with tilted illumination. In an immersion magnetic objective lens, electrons do not form a sharp crossover in the back-focal plane, which substantially reduces e-e interactions and the associated blur. The resulting limited field of view of the immersion objective lens in mirror mode can be eliminated by immersing the cathode of the electron gun in a magnetic field. A dual beam approach, where two beams with different landing energies illuminate the field of view, is used to mitigate the charging effects when the LEEM is used to image insulating surfaces. We have experimentally demonstrated that the negative charging effect, created by a partially absorbed mirror beam, is compensated by the positive charging effect of the secondary beam with a net electron yield exceeding 1. On substrates illuminated with a tilted beam near glancing incidence, large shadows are formed on even the smallest topographic features, easing their detection. On magnetic substrates, the magnetic flux leaking above the surface can be detected with tilted illumination and used to image domain walls with high contrast. (C) 2008 Elsevier B. V. All rights reserved.