3D Primitives Research Articles

Human shape recognition performance for 3D tactile display

The paper describes the relationship between the pin-matrix density of a tactile display and the recognition performance of displayed 3D shapes. Three types of pin-matrix tactile display, that generate 3D shapes, were used for the experiment. The pitch of pins was 2 mm, 3 mm, 5 mm each. We assumed that surfaces, edges, and vertices were primitive 3D shape information, so tested shapes were classified into these three categories. We assumed two types of finger touching mode: 1) fingertip-only, allowed full use of spatial shape information given to the fingertip; and 2) allowed tracing of the object. Recognition time and the classified error rate were measured. We obtained results on the relationship between pin pitch and recognition performance data. Regression curves for pin pitch and recognition time were plotted. A significance test of recognition time versus pin pitch was done. The error rate of identification versus pin pitch was described. Our results provide basic knowledge for developing tactile presentation devices.

Virtual reality publication of spiral ct-derived three-dimensional models: or, creation of spiral, CT-derived, three-dimensional VRML objects.

Three-dimensional models can be generated from slice images, such as those obtained from computed tomography (CT) and magnetic resonance imaging (MRI) using a variety of techniques. A popular method for rendering 3D anatomical models is the creation of polygonal mesh surfaces representing the boundary between tissues. Mesh surfaces can be rendered extremely quickly using conventional personal computers, without recourse to more expensive graphic workstations. The dissemination of three-dimensional (3D) models across the Internet has been made significantly easier by the definition of the Virtual Reality Markup Language (VRML) format. The VRML definition allows the parameters and relationships of 3D objects to be described in a text format. The text file can be transfered from a host computer to a remote client computer through the World Wide Web and viewed using readily available software (See Appendix). VRML is based on the definition of primitive 3D objects such as polygons and spheres. Consequently, the transition from a mesh surface derived from a clinical image data set to a VRML object is relatively simple, allowing for convenient and cost-effective dissemination of 3D clinical models across the internet.

Methods for updating the environment's geometric database in telerobotics

Abstract The paper deals with tools a human operator (HO) can use to complete, on-line, the 3D geometric database of the remote environment, even in case of bad condition of vision. The HO provides the system with the 3D geometric primitive of the object's model and the 2D data from the video image. The sensing system: a monocular video camera and a time of flight IR range finder, provides the system with figures relating to the 3D primitives (location, pose, size). Methods for location and pose determination of known objects and for modelling of unknown ones are presented and assessed. These methods are available for polyhedral and cylinder shaped objects, which represent the bases of most of industrial environments.

Obtaining Generic Parts from Range Images Using a Multi-view Representation

We describe a system for obtaining a "generic" parts-based 3D object representation. We use range image data as the input, obtaining a 3D object representation based on 12 geon-like 3D part primitives as the output. The 3D parts-based representation consists of parts detected in the image and their identities. Unlike previous work, we do not make simplifying assumptions such as the availability of perfect line drawings, perfect segmentation, or manual segmentation.We propose a novel method of specifying "generic" 3D parts, i.e., by means of surface adjacency graphs (SAGs). Using the SAGs, we derive an extremely compact multi-view representation of the part primitives, consisting of a total of only 74 views for all 12 primitives. Based on the multi-view representation of parts, we present a method of performing part segmentation from range images, given a good surface segmentation. This method for partsegmentation is more general than common approaches based on Hoffman and Richards′ "principle of transversality." We present two approaches for identifying the parts as one of the 12 3D part primitives. The first approach applies statistical pattern classification methods using parameters estimated by superquadric fitting. Five features derived from the estimated superquadric parameters are used to distinguish between the 12 part primitives. Classification error rates are estimated for k-nearest-neighbor and binary tree classifiers, for real as well as for synthetic range images. The second approach for part identification draws inferences from the distribution of angles between surface normals and the principal axis of a part.We show that intensity data can be used to recover from some misclassifications yielded by the purely range-based methods of part identification. A simple test is applied to check the concavity or convexity of the part silhouette in the intensity image. This serves as a reliable test of whether the part axis is straight orcurved.Results of part segmentation and identification are presented for real range images of several multi-part objects. Our system successfully performs part segmentation and identifies the parts.

3D geometrical features of anatomic structures: the example of the ulna and radius bones

This paper addresses two important issues of three-dimensional (3D) natural shape analysis. The first concerns the segmentation of these shapes into 3D primitives and the second deals with their geometric characterisation by means of intrinsic features. Restricting ourselves to 3D objects formed from two-dimensional (2D) cross-sectional adjacent slices (i.e., long bones), we present a method of contextual classification and results concerning the ulnar bone. With respect to the second issue, a curvature-torsion analysis of the medullar axis is introduced and the results are represented by means of torsion images. A first application to ulnar structures is given. It is shown that radius bones have zero torsion and that their curvatures can be studied in 2D. A preliminary statistical study of the 2D curvature of the radius is also presented.

A three-dimensional primitive extraction of long bones obtained from bi-dimensional Fourier descriptors

We propose a method for a 3D primitive extraction of long bones using a set of 2D Fourier descriptors. This set is shown to be stable, complete and endowed with geometrical invariancy properties. A polar diagram representation allowing a segmentation of 3D primitives is deduced. The method is illustrated in the case of ulna and radius bones.

Three‐dimensional hydrodynamics on finite elements. Part II: Non‐linear time‐stepping model

AbstractThe development and application of a non‐linear 3D hydrodynamic model are described. The model is based on the wave equation rearrangement of the primitive 3D shallow water equations with a general eddy viscosity formulation for the vertical shear. A Galerkin procedure is used to discretize these on simple sixnode elements: linear triangles in the horizontal with linear variations in the vertical. Resolution of surface, bottom and interfacial boundary layers is facilitated and total flexibility is preserved for specifying spatial and temporal variations in the vertical viscosity and density fields. A semi‐implicit time‐stepping algorithm allows the solutions for elevation and velocity to be uncoupled during each time step. The elevation solution is essentially a 2D wave equation calculation with a stationary sparse matrix representing the gravity waves. With nodal quadrature the subsequent velocity calculation is achieved by factoring only a tridiagonal diffusion matrix representing the vertical viscous terms. As a result the overall calculation scales computationally as only a 2D problem but provides the full 3D solution. Application to field‐scale problems is illustrated for the English Channel/Southern Bight system and the Lake Maracaibo system.

Recovering partial 3D wire frames descriptions from stereo data

The design of modules in the current version of the TINA stereo based 3D vision system responsible for the recovery of geometric descriptions and their subsequent integration into partial wire frame models are described. The approach differs considerably from that described in an earlier version of the TINA system 1,2. The strategy for the construction of partial wire frame descriptions is broken into the following three processing stages: 1. 1 Stereo processing: this is edged-based, and uses camera calibration information to provide a restriction on allowable matches between edges extracted from the left and right images. The algorithm does not, however, at this stage recover an accurate estimate of disparity of each pair of matched edges. 2. 2 Geometrical description: this relies on the identification of higher level 2D primitives from the edge strings in one, other or both images and their subsequent combination with stereo matching, and calibration data to allow the recovery of 3D primitives. 3. 3 Wire frame generation: based upon 2D and 3D proximity and connectivity heuristics potential wire frame components are identified.

The Pions Graphics System

During 1979, CERN began to evaluate how interactive computer graphics displays could aid the analysis of high-energy physics experiments at the new Super Proton Synchrotron collider. This work led to PIONS, a 3D graphics system, which features the ability to store and view hierarchical graphics structures in a directed-acyclic-graph database. It is possible to change the attributes of these structures by making selections on nongraphical information also stored in the database. PIONS is implemented as an object-oriented message-passing system based on Small Talk design principles. It supports multiple viewing transformations, logical input devices, and 2D and 3D primitives. The design allows full use to be made of display hardware that provides dynamic 3D picture transformation.

Graphics abstraction model for SEICAD

The data abstraction approach to design of a Graphics Abstraction Model (GAM) for 3D solid objects and 2D picture views is described. The main idea is to represent graphical objects including instances of certain views by abstraction data types and data abstraction models using functional dependencies, which basically use the algebraic approach. Compound objects constructed by several ACTION operations (ASSEMBLE, UNION, etc.) on primitive 3D entities can be handled as compound entities. Points, lines, and faces are defined as data abstractions. General drawing facilities such as points, lines and faces also can be used by commands under 3D coordinates data.

Virtual Geographic World: The Web-based 3DCIS

To design and implement web-based 3D GIS, the strategic linkage of Java and VRML is first regarded: 3D feature format definition in the passion of conventional GIS including aspatial attributes, 3D feature indexing, 3D analytical operations such as selection, buffering, and near, metric operation such as distance measurement and statistical description, and 3D visualization. In 3D feature format definition, the following aspects are considered: aspatial attributes, spatial information for 3D primitives, multimedia data, visualization information for VRML specification. Lantern operator is newly introduced in this 3D GIS. Because this system is implemented by Java applet, any client with Java-enable browser including VRML browser plug-in can utilize the new style of 3D GIS function in the virtual space.