RBF Volume Ray Casting on Multicore and Manycore CPUs

Modern supercomputers enable increasingly large N‐body simulations using unstructured point data. The structures implied by these points can be reconstructed implicitly. Direct volume rendering of radial basis function (RBF) kernels in domain‐space offers flexible classification and robust feature reconstruction, but achieving performant RBF volume rendering remains a challenge for existing methods on both CPUs and accelerators. In this paper, we present a fast CPU method for direct volume rendering of particle data with RBF kernels. We propose a novel two‐pass algorithm: first sampling the RBF field using coherent bounding hierarchy traversal, then subsequently integrating samples along ray segments. Our approach performs interactively for a range of data sets from molecular dynamics and astrophysics up to 82 million particles. It does not rely on level of detail or subsampling, and offers better reconstruction quality than structured volume rendering of the same data, exhibiting comparable performance and requiring no additional preprocessing or memory footprint other than the BVH. Lastly, our technique enables multi‐field, multi‐material classification of particle data, providing better insight and analysis.     

Effects of prior plastic deformation on the martensitic transformation in oriented single crystals of Au-47.5 at.% Cd

Oriented single crystal samples of phase Au-47.5 at.% Cd were progressively compressed along [110], [111] and [112] axes, causing each sample to deform with a different {110} 001 slip multiplicity and, therefore, develop a different defect substructure. The effects of the existing substructure upon subsequent martensite and reverse transformation were studied as a function of deformation for each sample, using a resistance technique.It was observed that for small amounts of reduction in thickness ( 5%), the greater the work-hardening rate associated with deformation, the greater the enhancement of the martensite nucleation (increase inM _s temperature). It is suggested that {110} 1¯10 slip band intersections, produced during prior deformation, are responsible for this enhancement. For larger amounts of reduction in thickness (>5%), for the [110] and [111] samples, martensite nucleation becomes less enhanced, and finally inhibited. Deformation of the [112] sample has little effect upon martensite nucleation behaviour for any amount of reduction in thickness, because it undergoes almost single slip and presumably, few slip band intersections are formed. There is no apparent correlation between prior deformation andA _s temperature.The greater the work-hardening rate associated with deformation, the greater the increase in difficulty of propagation of both the martensite and the austenite as a function of reduction in thickness. Defect pinning of the transformation interface is suggested as a possible mechanism to explain this observation. Also, practically the same increase in difficulty of propagation is observed for the A M and M A transformations for any sample, suggesting that the defects responsible for pinning are not erased after the two cycles that the sample is subjected to during testing.Submitted in partial fulfilment of the requirements for the degree of Master of Science at the Polytechnic Institute of Brooklyn by Martin L. Green.     

THE ECOLOGY OF POLITICAL REFORM

In several studies of political behavior in Chicago, Thomas Guterbock has identified “localism,” an affectual commitment to a bounded subcommunity, as the key sentiment generating electoral support for the Democratic organization. Localistic sentiment has been linked to pro-machine voting, Guterbock suggests, because the organization is perceived as the source of valuable support for maintaining the neighborhood. A replication of the Guterbock study in Memphis finds that localism, measured by the same aggregate indicators selected by Guterbock, was a strong predictor of support for the reformers who challenged the Crump machine in elections from 1948–1955. By the postwar era, it seems, the Memphis machine was losing the will and capacity to respond to demands for community development, thereby losing its standing as a valuable resource for the neighborhood patriots whose political choices were dictated by instrumental considerations. This finding underscores that the link between localism and political behavior depended upon the nature of the political alternatives available to the electorate.     

Self-radiation damage in Gd2Ti2O7

The effects of self-radiation damage from alpha decay in Gd₂Ti₂O₇ were investigated by studying specimens doped with ²⁴⁴Cm. The radiation-induced microstructure consists of individual amorphous tracks from both the alpha-recoil particles and the spontaneous fission fragments. The eventual overlap of the tracks at higher doses leads to a completely amorphous state. The self-radiation damage increases the volume, dissolution rate, and fracture toughness. Electron-beam recrystallization of the amorphous state results in the formation of fine microcrystallites on the order of 0.05 μm in size.     

Sequential Monte Carlo Adaptation in Low‐Anisotropy Participating Media

This paper presents a novel method that effectively combines both control variates and importance sampling in a sequential Monte Carlo context. The radiance estimates computed during the rendering process are cached in a 5D adaptive hierarchical structure that defines dynamic predicate functions for both variance reduction techniques and guarantees well‐behaved PDFs, yielding continually increasing efficiencies thanks to a marginal computational overhead. While remaining unbiased, the technique is effective within a single pass as both estimation and caching are done online, exploiting the coherency in illumination while being independent of the actual scene representation. The method is relatively easy to implement and to tune via a single parameter, and we demonstrate its practical benefits with important gains in convergence rate and competitive results with state of the art techniques.     

Interactive Rendering with Coherent Ray Tracing

For almost two decades researchers have argued that ray tracing will eventually become faster than the rasterization technique that completely dominates todays graphics hardware. However, this has not happened yet. Ray tracing is still exclusively being used for off-line rendering of photorealistic images and it is commonly believed that ray tracing is simply too costly to ever challenge rasterization-based algorithms for interactive use. However, there is hardly any scientific analysis that supports either point of view. In particular there is no evidence of where the crossover point might be, at which ray tracing would eventually become faster, or if such a point does exist at all.
This paper provides several contributions to this discussion: We first present a highly optimized implementation of a ray tracer that improves performance by more than an order of magnitude compared to currently available ray tracers. The new algorithm make better use of computational resources such as caches and SIMD instructions and better exploits image and object space coherence. Secondly, we show that this software implementation can challenge and even outperform high-end graphics hardware in interactive rendering performance for complex environments. We also provide an brief overview of the benefits of ray tracing over rasterization algorithms and point out the potential of interactive ray tracing both in hardware and software.