William P. Horn

Progressive forest split compression

In this paper we introduce the Progressive Forest Split (PFS) representation, a new adaptive refinement scheme for storing and transmitting manifold triangular meshes in progressive and highly compressed form. As in the Progressive Mesh (PM) method of Hoppe, a triangular mesh is represented as a low resolution polygonal model followed by a sequence of refinement operations, each one specifying how to add triangles and vertices to the previous level of detail to obtain a new level. The PFS format shares with PM and other refinement schemes the ability to smoothly interpolate between consecutive levels of detail. However, it achieves much higher compression ratios than PM by using a more complex refinement operation which can, at the expense of reduced granularity, be encoded more efficiently. A forest split operation doubling the number n of triangles of a mesh requires a maximum of approximately 3:5n bits to represent the connectivity changes, as opposed to approximately (5 + log2(n))n bits in PM. We describe algorithms to efficiently encode and decode the PFS format. We also show how any surface simplification algorithm based on edge collapses can be modified to convert single resolution triangular meshes to the PFS format. The modifications are simple and only require two additional topological tests on each candidate edge collapse. We show results obtained by applying these modifications to the Variable Tolerance method of Gueziec. CR

Geometry coding and VRML

The virtual-reality modeling language (VRML) is rapidly becoming the standard file format for transmitting three-dimensional (3-D) virtual worlds across the Internet. Static and dynamic descriptions of 3-D objects, multimedia content, and a variety of hyperlinks can be represented in VRML files. Both VRML browsers and authoring tools for the creations of VRML files are widely available for several different platforms. In this paper, we describe the topologically assisted geometric compression technology included in our proposal for the VRML compressed binary format. This technology produces significant reduction of file sizes and, subsequently, of the time required for transmission of such filed across the Internet. Compression ratios of 50:1 or more are achieved for large models. The proposal also includes a binary encoding to create compact, rapidly parsable binary VRML files. The proposal is currently being evaluated by the Compressed Binary Format Working Group of the VRML consortium as a possible extension of the VRML standard. In the topologically assisted compression scheme, a polyhedron is represented using two interlocking trees: a spanning tree of vertices and a spanning tree of triangles. The connectivity information represented in other compact schemes, such as triangular strips and generalized triangular meshes, can be directly derived from this representation. Connectivity information for large models is compressed with storage requirements approaching one bit per triangle. A variable-length, optionally lossy compression technique is used for vertex positions, normals, colors, and texture coordinates. The format supports all VRML property binding conventions.

Simplicial maps for progressive transmission of polygonal surfaces

We present a new method for (1) automatically generating multiple Levels Of Detail (LODs) of a polygonal surface, (2) progressively loading, or transmitting, and displaying a surface, and for (3) changing interactively the LOD when displaying. We build the LODs using any algorithm that performs edge collapses and certain vertex removals to simplify surfaces, and provides an ordered list of ordered vertex pairs (edge collapse specifications). We propose a Surface Partition for encoding surface LODs: we define vertex and triangle levels during simplification; vertices and triangles are partitioned and sorted according to their level, and are passed to the display algorithm in decreasing level order, one level at a time, together with a vertex representatives array. Each level of vertices and triangles, together with higher levels and the vertex representatives, form a valid surface. The vertex representatives array encodes a succession of simplicial maps between the highest resolution LOD and other LODs. We propose a data structure using a Directed Acyclic Graph (DAG) for recording a partial ordering among edge collapses, and varying the LODs across the surface. We describe an implementation of our method in VRML. Key-words : Simplicial Map, Edge Collapse, Vertex and Triangle Levels, Surface Levels of Detail, Surface Partition, Progressive Transmission and Display, Dynamic Simplification.

Workload characterization of selected JEE-based Web 2.0 applications

Web 2.0 represents the evolution of the web from a source of information to a platform. Network advances have permitted users to migrate from desktop applications to so-called Rich Internet Applications (RIAs) characterized by thin clients, which are browser-based and store their state on managed servers. Other Web 2.0 technologies have enabled users to more easily participate, collaborate, and share in web-based communities. With the emergence of wikis, blogs, and social networking, users are no longer only consumers, they become contributors to the collective knowledge accessible on the web. In another Web 2.0 development, content aggregation is moving from portal-based technologies to more sophisticated so-called mashups where aggregation capabilities are greatly expanded. While Web 2.0 has generated a great deal of interest and discussion, there has not been much work on analyzing these emerging workloads. This paper presents a detailed characterization of several applications that exploit Web 2.0 technologies, running on an IBM Power5 system, with the goal of establishing, whether the server-side workloads generated by Web 2.0 applications are significantly different from traditional web workloads, and whether they present new challenges to underlying systems. In this paper, we present a detailed characterization of three Web 2.0 workloads, and a synthetic benchmark representing commercial workloads that do not exploit Web 2.0, for comparison.

A theorem to determine the spatial containment of a point in a planar polyhedron

Abstract A theorem is presented which addresses the containment of a point within a polyhedron composed of planar faces. The theorem provides a basis for a point-in-polyhedron algorithm. The algorithm uses information contained in a winged-edge representation of the polyhedron. If the test point is closer to a face of the polyhedron than to any other face, vertex, or edge, then the test is based on the orientation of the face. If the point is closer to an edge (vertex) than to any other face, vertex, or edge, then the test is based on the classification of the edge (vertex). The classification of edges and vertices can be performed in a preprocessing step. The resultant algorithm has the advantages of being simple and robust.

Graph programming interface (GPI): a linear algebra programming model for large scale graph computations

Graph processing is becoming a crucial component for analyzing big data arising in many application domains such as social and biological networks, fraud detection, and sentiment analysis. As a result, a number of computational models for graph analytics have been proposed in the literature to help users write efficient large scale graph algorithms. In this paper we present an alternative model for implementing graph algorithms using a linear algebra based specification. We first specify a set of linear algebra primitives that allows users to express graph algorithms by composition of linear algebra operations. We then describe a high performance implementation of these primitives and its integration with the Spark framework to achieve the scalability we need for large shared-memory systems. We provide an overview of our implementation and also compare and contrast the expressiveness and performance of various algorithms implemented with our approach with that of the current Spark GraphX implementation of those algorithms.

An advanced accounting service for AIX Systems

Resource usage is important input for a number of IT processes including those related to: financial management, capacity planning; service level management; and configuration management. Accounting systems in traditional UNIX/Linux environments generate a usage record at the end of each process. Administrators periodically use standard accounting system utilities to summarize resource usage using the user and application data recorded with each of these records. Recent advances in dynamic LPAR technologies and service oriented architectures have placed new requirements on the metering of resource usage. In a Dynamic LPAR environment, allocations must be measured and processed to obtain accurate information on resource usage. Transactions performed using service oriented architectures deployed on heterogeneous, distributed systems introduce new challenges for metering resource usage based on transaction classes. In this paper we present the design and implementation of a J2EE-based accounting service which exposes manageability and reporting interfaces for the AIX advanced accounting system. The reporting interface can be used to generate process-based, LPAR-based and transaction-based usage reports.

Graph Programming Interface (GPI): A Linear Algebra Programming Model for Large Scale Graph Computations

Graph processing is becoming a crucial component for analyzing big data arising in many application domains such as social and biological networks, fraud detection, and sentiment analysis. As a result, a number of computational models for graph analytics have been proposed in the literature to help users write efficient large scale graph algorithms. In this paper we present an alternative model for implementing graph algorithms using a linear algebra based specification. We first specify a set of linear algebra primitives that allows users to express graph algorithms by composition of linear algebra operations. We then describe a high performance implementation of these primitives using C

Simplification of surface annotations

++