Extended specifications and test data sets for data levelcomparisons of direct volume rendering algorithms

Direct volume rendering (DVR) algorithms do not generate intermediate geometry to create a visualization, yet they produce countless variations in the resulting images. Therefore, comparative studies are essential for objective interpretation. Even though image and data level comparison metrics are available, it is still difficult to compare results because of the numerous rendering parameters and algorithm specifications involved. Most of the previous comparison methods use information from the final rendered images only. We overcome limitations of image level comparisons with our data level approach using intermediate rendering information. We provide a list of rendering parameters and algorithm specifications to guide comparison studies. We extend Williams and Uselton's rendering parameter list with algorithm specification items and provide guidance on how to compare algorithms. Real data are often too complex to study algorithm variations with confidence. Most of the analytic test data sets reported are often useful only for a limited feature of DVR algorithms. We provide simple and easily reproducible test data sets, a checkerboard and a ramp, that can make clear differences in a wide range of algorithm variations. With data level metrics, our test data sets make it possible to perform detailed comparison studies. A number of examples illustrate how to use these tools     

Time and Space Optimal Data Parallel Volume Rendering Using Permutation Warping

In this paper we present a data parallel volume rendering algorithm that possesses numerous advantages over prior published solutions. Volume rendering is a three-dimensional graphics rendering algorithm that computes views of sampled medical and simulation data, but has been much slower than other graphics algorithms because of the data set sizes and the computational complexity. Our algorithm usespermutation warpingto achieve linear speedup (run time is O(S/P) forPprocessors whenP\= O(S/logS) forS\=n³samples), linear storage (O(S)) for large data sets, arbitrary view directions, and high-quality filters. We derived a new processor permutation assignment of five passes (our prior known solution was eight passes), and a new parallel compositing technique that is essential for scaling linearly on machines that have more processors than view rays to process (P>n²). We show a speedup of 15.7 for a 16k processor over a 1k processor MasPar MP-1 (16 is linear) and two frames/second with a 128³volume and trilinear view reconstruction. In addition, we demonstrate volume sizes of 256³, constant run time over angles 5 to 75°, filter quality comparisons, and communication congestion of just 19 to 29\%.     

2D and 3D Optimal Parallel Image Warping

Spatial image warping is useful for image processing and graphics. In this paper, we present concurrent-read-exclusive-write (CREW) and exclusive-read-exclusive-write (EREW) parallel-random-access-machine (PRAM) algorithms that achieve O(1) asymptotic run time. The significant result is the creative processor assignment that results in an EREW PRAM algorithm. The forward algorithm calculates any nonscaling affine transform including arbitrary skewings, translations, and rotations. The EREW algorithm is the most efficient in practice, and the MasPar MP-1 with 16K processors rotates a 4-million-element image in under a second and a 2-million-element volume in one-half of a second. This high performance allows interactive viewing of volumes from arbitrary viewpoints and illustrates linear speedup. This practical efficiency is analyzed and illustrated by using a bridging model of computation. We develop the mixed cost communication machine (MCCM) to quantify the communication costs and correlate these costs to the MasPar MP-1. The forward algorithm has provable N = 1 congestion on the MCCM, while the backward algorithm has congestion N > 1 which varies with the transform. There are also important quality advantages using our direct warping techniques; empirical measurements are given to provide comparisons to multipass warps.     

Identification of group VS116 strains among Borrelia burgdorferi sensu lato grown from the hard tick, Ixodes ricinus (Linnaeus, 1758) by off-coupled restriction fragment length polymorphism analysis

The degree of chemical shift similarity for homologous proteins has been determined from a chemical shift database of over 50 proteins representing a variety of families and folds, and spanning a wide range of sequence homologies. After sequence alignment, the similarity of the secondary chemical shifts of C alpha protons was examined as a function of amino acid sequence identity for 37 pairs of structurally homologous proteins. A correlation between sequence identity and secondary chemical shift rmsd was observed. Important insights are provided by examining the sequence identity of homologous proteins versus percentage of secondary chemical shifts that fall within 0.1 and 0.3 ppm thresholds. These results begin to establish practical guidelines for the extent of chemical shift similarity to expect among structurally homologous proteins.     

Spontaneous prejudice in context: Variability in automatically activated attitudes.

The goal of the research reported in this article was to examine whether automatic group attitudes and stereotypes, commonly thought to be fixed responses to a social category cue, are sensitive to change in the situational context. Two experiments demonstrated such variability of automatic responses due to changes in the stimulus context. In Study 1 White participants' implicit attitudes toward Blacks varied as a result of exposure to either a positive (a family barbecue) or a negative (a gang incident) stereotypic situation. Study 2 demonstrated similar context effects under clearly automatic processing conditions. Here, the use of different background pictures (church interior vs. street corner) for Black and White face primes affected participants' racial attitudes as measured by a sequential priming task. Implications for the concept of automaticity in social cognition are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proteus: A reconfigurable computational network for computer vision

The Proteus architecture is a highly parallel, multiple instruction, multiple data machine (MIMD) optimized for large granularity tasks such as machine vision and image processing. The system can achieve 20 gigaflops (80 gigaflops peak). It accepts data via multiple serial links at a rate of up to 640 MB/S. The system employs a hierarchical reconfigurable interconnection network with the highest level being a circuit-switchedenhanced hypercube, serial interconnection network for internal data transfers. The system is designed to use 256 to 1024 RISC processors. The processors use 1-MB externalread/write allocating caches for reduced multiprocessor contention. The system detects, locates, and replaces faulty subsystems using redundant hardware to facilitatefault tolerance. The parallelism is directly controllable through an advanced software system for partitioning, scheduling, and development. System software includes a translator for the INSIGHT language, a parallel debugger, lowand high-level simulators, and a message-passing system for all control needs. Image-processing application software includes a variety of point operators, neighborhood operators, convolution, and the mathematical morphology operations of binary and gray-scale dilation, erosion, opening, and closing.     

High order projection methods of moment- and collocation-type for nonlinear boundary value problems

Approximations to an isolated solution of a two point boundary value problem are determined by projection methods with piecewise polynomial functions. Some principles are derived which lead in a uniform way to statements of high-order convergence for a variety of moment-type methods and collocation methods with Gaussian nodes.     

Cache write generate for parallel image processing on shared memoryarchitectures

We investigate cache write generate, our cache mode invention. We demonstrate that for parallel image processing applications, the new mode improves main memory bandwidth, CPU efficiency, cache hits, and cache latency. We use register level simulations validated by the UW-Proteus system. Many memory, cache, and processor configurations are evaluated.     

Framing interethnic ideology: Effects of multicultural and color-blind perspectives on judgments of groups and individuals.

In 3 experiments, White American college students received a message advocating either a color-blind or a multicultural ideological approach to improving interethnic relations and then made judgments about various ethnic groups and individuals. Relative to a color-blind perspective, the multicultural perspective led to stronger stereotypes, greater accuracy in these stereotypes, and greater use of category information in judgments of individuals. This increase in between-category differentiation occurred both for attributes that favored the in-group and for attributes that favored the out-group and was also paired in some cases with greater overall positivity toward the out-group. The findings lead us to question the implicit assumption driving the majority of social psychological efforts at prejudice reduction: that the categorization process leads to prejudice, and that the relevance of social categories must therefore be de-emphasized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)