Methods to implement stochastic simulations on the graphics processing unit (GPU) have been developed. These algorithms are used in a simulation of microassembly and nanoassembly with optical tweezers, but are also directly compatible with simulations of a wide variety of assembly techniques using either electrophoretic, magnetic, or other trapping techniques. Significant speedup is possible for stochastic particle simulations when using the GPU, included in most personal computers (PCs), rather than the central processing unit (CPU) that handles most calculations. However, a careful analysis of the accuracy and precision when using the GPU in stochastic simulations is lacking and is addressed here. A stochastic simulation for spherical particles has been developed and mapped onto stages of the GPU hardware that provide the best performance. The results from the CPU and GPU implementation are then compared with each other and with well-established theory. The error in the mean ensemble energy and the diffusion constant is measured for both the CPU and the GPU implementations. The time taken to complete several simulation experiments on each platform has also been measured and the speedup attained by the GPU is then calculated.

This paper describes a computational framework for constructing point clouds using digital projection patterns. The basic principle behind the approach is to project known patterns on the object using a digital projector. A digital camera is then used to take images of the object with the known projection patterns imposed on it. Due to the presence of 3D faces of the object, the projection patterns appear distorted in the images. The images are analyzed to construct the 3D point cloud that is capable of introducing the observed distortions in the images. The approach described in this paper presents three advances over the previously developed approaches. First, it is capable of working with the projection patterns that have variable fringe widths and curved fringes and hence can provide improved accuracy. Second, our algorithm minimizes the number of images needed for creating the 3D point cloud. Finally, we use a hybrid approach that uses a combination of reference plane images and estimated system parameters to construct the point cloud. This approach provides good run-time computational performance and simplifies the system calibration.

Inspection of machined objects is one of the most important quality control tasks in the manufacturing industry. Ideally, inspection processes should be able to work directly on scan point data. Scan data, however, are typically very large scale (i.e., many points), unorganized, noisy, and incomplete. Therefore, direct processing of scanned points is problematic. Many of these problems may be reduced if reconstruction methods exploit diverse scan data , that is, information about the properties of the scanned object. This paper describes this concept and proposes new methods for extraction and processing of diverse scan data: (1) extraction (detection of a scanned object’s sharp features by the sharp feature detection method) and (2) processing (scan data reduction by the geometric bilateral filter method). The proposed methods are applied directly on the scanned points and are completely automatic, fast, and straightforward to implement. Finally, this paper demonstrates the integration of the proposed methods into the computational inspection process.

A two-dimensional (2D) graphics hierarchical representation framework and an on-demand content delivery mechanism for facilitating mobile engineering collaboration are presented in this paper. Multi-level graphics content sub-division is utilized to transform large engineering graphics into multiple levels of Scalable Vector Graphics (SVG) content. The hierarchical structure of the SVG content that maintains the relationship between the sub-divided content is formed during the process of sub-division. The divided content is selectively delivered and rendered on the mobile devices in an on-demand fashion. A prototypical system of the proposed approach is implemented and the performance of the framework is evaluated.

This paper describes recently developed procedures for local conformal refinement and coarsening of all-hexahedral unstructured meshes. Both refinement and coarsening procedures take advantage of properties found in the dual or “twist planes” of the mesh. A twist plane manifests itself as a conformal layer or sheet of hex elements within the global mesh. We suggest coarsening techniques that will identify and remove sheets to satisfy local mesh density criteria while not seriously degrading element quality after deletion. A two-dimensional local coarsening algorithm is introduced. We also explain local hexahedral refinement procedures that involve both the placement of new sheets, either between existing hex layers or within an individual layer. Hex elements earmarked for refinement may be defined to be as small as a single node or as large as a major group of existing elements. Combining both refinement and coarsening techniques allows for significant control over the density and quality of the resulting modified mesh.

Parameterization of 3D meshes is important for many graphic and CAD applications, in particular for texture mapping, remeshing, and morphing. Current parameterization methods for closed manifold genus- g meshes usually involve cutting the mesh according to the object generators, adjusting the resulting boundary and then determining the 2D parameterization coordinates of the mesh vertices, such that the flattened triangles are not too distorted and do not overlap. Unfortunately, adjusting the boundary distorts the resulting parameterization, especially near the boundary. To overcome this problem for genus- g meshes we first address the special case of closed manifold genus-1 meshes by presenting cyclic boundary constraints . Then, we expand the idea of cyclic boundary constraints by presenting a new generalized method developed for planar parameterization of closed manifold genus- g meshes. A planar parameterization is constructed by exploiting the topological structure of the mesh. This planar parameterization can be represented by a surface which is defined over parallel g -planes that represents g -holes. The proposed parameterization method satisfies the nonoverlapping requirement for any type of positive barycentric weights, including asymmetric weights. Moreover, convergence is guaranteed according to the Gauss-Seidel method.

An approach to modeling heterogeneous objects as multidimensional point sets with multiple attributes (hypervolumes) is presented. Attributes given at each point represent object properties of arbitrary nature (material, physical, etc.). A proposed theoretical framework is based on a hybrid model of geometry and attributes combining a cellular representation and a functionally based constructive representation of dimensionally non-homogeneous entities. Hypervolume model components such as objects, operations and relations are introduced and outlined. We present examples of modeling a multi-layer geological structure with cavities and wells, time-dependent adaptive mesh generation, and conversion of a 3D implicit complex to the cellular representation.

In this article we review commonly used data translation software for Windows PC-based virtual reality (VR) scene graphs. The goal is efficient data input and output from various VR software. VR using Windows OS is considered because it is growing, and is likely to become significant in the years to come. Also many of Windows solutions currently operate on LINUX or UNIX, so it represents interoperability to some extent. This article does not deal with the user tracking software in VR, it however deals with software capabilities for the scene graph content creation from a rendering, navigation and animation standpoint. Among others, in particular we review Pro/Engineer-VR software interface, because such an interface is highly representative of the challenges and difficulties involved. Data conversion represents a significant challenge, e.g. according to a National Institute of Standards and Technology (NIST) study, imperfect interoperability is costing the US automotive supply chain at least one billion dollars per year [1].

Virtual reality applications are making valuable contributions to the field of product realization. This paper presents an assessment of the hardware and software capabilities of VR technology needed to support a meaningful integration of VR applications in the product life cycle analysis. Several examples of VR applications for the various stages of the product life cycle engineering are presented as case studies. These case studies describe research results, fielded systems, technical issues, and implementation issues in the areas of virtual design, virtual manufacturing, virtual assembly, engineering analysis, visualization of analysis results, and collaborative virtual environments. Current issues and problems related to the creation, use, and implementation of virtual environments for engineering design, analysis, and manufacturing are also discussed.