Getting to the Point...?

This viewpoint focuses on the utility of point primitives for computer graphics and visualization. The author analyzes recent advancements in modeling, rendering, and animation, and he compares essential properties of point primitives with those of triangles and voxels.     

Image‐Based Surface Compression

We present a generic framework for compression of densely sampled three‐dimensional (3D) surfaces in order to satisfy the increasing demand for storing large amounts of 3D content. We decompose a given surface into patches that are parameterized as elevation maps over planar domains and resampled on regular grids. The resulting shaped images are encoded using a state‐of‐the‐art wavelet image coder. We show that our method is not only applicable to mesh‐ and point‐based geometry, but also outperforms current surface encoders for both primitives.     

Extreme simplification and rendering of point sets using algebraic multigrid

We present a novel approach for extreme simplification of point set models, in the context of real-time rendering. Point sets are often rendered using simple point primitives, such as oriented discs. However, this requires using many primitives to render even moderately simple shapes. Often, one wishes to render a simplified model using only a few primitives, thus trading accuracy for simplicity. For this goal, we propose a more complex primitive, called a splat, that is able to approximate larger and more complex surface areas than oriented discs. We construct our primitive by decomposing the model into quasi-flat regions, using an efficient algebraic multigrid algorithm. Next, we encode these regions into splats implemented as planar support polygons textured with color and transparency information and render the splats using a special blending algorithm. Our approach combines the advantages of mesh-less point-based techniques with traditional polygon-based techniques. We demonstrate our method on various models.     

Synchrony vs Asynchrony in Communication Primitives

We study, from the expressiveness point of view, the impact of synchrony in the communication primitives that arise when combining together some common and useful programming features like arity of data, communication medium and possibility of pattern matching. For some primitives, we show how their synchronous version can be encoded in their asynchronous counterpart via a fully abstract encoding, thus proving that the two versions have the same expressive power. For the remaining primitives, we prove that no ‘reasonable’ encoding can exist, thus proving that synchrony adds expressiveness to the language.     

New aspect-oriented constructs for security hardening concerns

In this paper, we present new pointcuts and primitives to Aspect-Oriented Programming (AOP) languages that are needed for systematic hardening of security concerns. The two proposed pointcuts allow to identify particular join points in a program's control-flow graph (CFG). The first one is the GAFlow, Closest Guaranteed Ancestor, which returns the closest ancestor join point to the pointcuts of interest that is on all their runtime paths. The second one is the GDFlow, Closest Guaranteed Descendant, which returns the closest child join point that can be reached by all paths starting from the pointcut of interest. The two proposed primitives are called ExportParameter and ImportParameter and are used to pass parameters between two pointcuts. They allow to analyze a program's call graph in order to determine how to change function signatures for passing the parameters associated with a given security hardening. We find these pointcuts and primitives to be necessary because they are needed to perform many security hardening practices and, to the best of our knowledge, none of the existing ones can provide their functionalities. Moreover, we show the viability and correctness of the proposed pointcuts and primitives by elaborating and implementing their algorithms and presenting the result of explanatory case studies.     

基于直线段跟踪的手绘图元离线识别方法*

手绘图形是人类思维外化和表达意图的一种有效方式,如何有效地提取手绘在图纸上的图形元素是理解绘图者意图的关键问题。鉴于手绘图形是由基本图元组合构成,采用层次结构逐步实现图元提取的思想,提出了一种手绘基本图元（线段、弧、圆和椭圆）的离线识别方法。在提取图形笔画骨架像素的基础上,跟踪骨架像素得到图形的直线段描述;通过对直线段序列的分析,进行直线段序列的断开和连接处理,形成图元的曲线段描述,通过对图元曲线段描述的分析得出图元的几何参数。实验表明,该方法能够以高精确度快速识别出图像中包含的手绘图元,具有良好的稳定性     

PKR-inhibitor binds efficiently with human microtubule affinity-regulating kinase 4

MAP/microtubule affinity-regulating kinase 4 (MARK4) plays a central role in the cellular physiology, and it is inseparably linked with many human diseases including cancer, diet induced obesity, type2 diabetes and neurodegenerative disorders. Here, we studied the interaction of PKR-inhibitor with two variants of human MARK4. One variant is named as MARK4-F1 which has 59 N-terminal residues along with kinase domain while another variant is MARK4-F2 which has kinase domain only. Molecular-docking, molecular dynamics (MD) simulation and fluorescence-binding studies were undertaken to understand the role of N-terminal 59-residues in the binding of substrate/inhibitors. Molecular docking studies revealed that the PKR-inhibitor binds in the large hydrophobic cavity of the kinase domain of MARK4 through several hydrophobic and hydrogen-bonded interactions. Furthermore, MD simulation showed a stable parameters for the complexes of both MARK4-F1 and MARK4-F2 to PKR-inhibitor with marginal difference in their binding affinities. A significant decrease in the fluorescence intensity of MARK4 was observed on successive addition of the PKR-inhibitor. Using fluorescence data we have calculated the binding-affinity and the number of binding site of PKR-inhibitor to the MARK4. A significantly high binding affinity was observed for the PKR-inhibitor to the MARK4 variants. However, there is no any significant difference in the binding affinity of PKR-inhibitor to the MARK4 variants was observed, indicating that 59 N-terminal residues of MARK4-F1 are not playing a crucial role in the ligand binding. The present study will provide an insights into designing of new PKR-inhibitor derivative as potent and selective therapeutic agent against many life threatening diseases which are associated with MARK4.     

Discovery of Intrinsic Primitives on Triangle Meshes

The discovery of meaningful parts of a shape is required for many geometry processing applications, such as parameterization, shape correspondence, and animation. It is natural to consider primitives such as spheres, cylinders and cones as the building blocks of shapes, and thus to discover parts by fitting such primitives to a given surface. This approach, however, will break down if primitive parts have undergone almost‐isometric deformations, as is the case, for example, for articulated human models. We suggest that parts can be discovered instead by finding intrinsic primitives, which we define as parts that posses an approximate intrinsic symmetry. We employ the recently‐developed method of computing discrete approximate Killing vector fields (AKVFs) to discover intrinsic primitives by investigating the relationship between the AKVFs of a composite object and the AKVFs of its parts. We show how to leverage this relationship with a standard clustering method to extract k intrinsic primitives and remaining asymmetric parts of a shape for a given k. We demonstrate the value of this approach for identifying the prominent symmetry generators of the parts of a given shape. Additionally, we show how our method can be modified slightly to segment an entire surface without marking asymmetric connecting regions and compare this approach to state‐of‐the‐art methods using the Princeton Segmentation Benchmark.     

Hopfield Neural Network Based Stereo Matching Algorithm

In this paper, a neural network based optimization method is described in order to solve the problem of stereo matching for a set of primitives extracted from a stereoscopic pair of images. The neural network used is the 2D Hopfield network. The matching problem amounts to the minimization of an energy function involving specified stereoscopic constraints. This function reaches its minimum when these constraints are satisfied. The network converges to its stable state when the minimum is reached. In the initial step, the primitives to match are extracted from the stereoscopic pair of images. The primitives we use are specific points of interest. The feature extraction technique is the one developed by Moravec, and called the interest operator. Its output comprises mostly corners or feature points with high variance. The Hopfield network is represented as a N _l × N _r matrix of neurons, where N _l is the number of features in the left image and N _r the number of features in the right one. An update of the state of each neuron is done in order to perform the network evolution and then allowing it to settle down into a stable state. In the stable state, each neuron represents a possible match between a left candidate and a right one.     

New application methods for word-oriented cryptographic primitives

Modern software oriented symmetric ciphers have become a key feature in utilizing word-oriented cryptographic primitives.Using the output sequence,in the order of its generation,of a word-oriented cryptographic primitive in the same way as traditional bit-oriented primitives,we can expose the intrinsic weakness of these primitives,especially for word-oriented linear feedback shift registers,T-functions,and so on.Two new methods for using word-oriented cryptographic primitives are presented in this paper,that is,the extracted state method and cascading extracted coordinate method.Using a T-function as an example,we research the different cryptographic properties of the output sequences of the original method and the two proposed methods,focusing mainly on period,linear complexity,and k-error linear complexity.Our conclusions show that the proposed methods could enhance at low cost the cryptographic properties of the output sequence.As a result,since the new methods are simple and easy to implement,they could be used to design new word-oriented cryptographic primitives.     

Two-dimensional Potential Fields for Advanced Implicit Modeling Operators

Current methods for building models using implicit volume techniques present problems defining accurate and controllable blend shapes between implicit primitives. We present new methods to extend the freedom and controllability of implicit volume modeling. The main idea is to use a free‐form curve to define the profile of the blend region between implicit primitives. The use of a free‐form implicit curve, controlled point‐by‐point in the Euclidean user space, allows us to group boolean composition operators with sharp transitions or smooth free‐form transitions in a single modeling metaphor. This idea is generalized for the creation, sculpting and manipulation of volume objects, while providing the user with simplicity, controllability and freedom in implicit modeling. ACM CSS: I.3.5 Computational Gemoetry and Object Modeling—Curve, surface, solid, and object representations     

A representation language for behavior and function: FBRL

Although a lot of researchers have pointed out the significance of functional representation, the general relations between function and behavior are not yet fully understood. We consider the knowledge of each component in a system as consisting of two elements. One is a necessary and sufficient concept far simulation of the component which we call the behavior model. The other is the interpretation of the behavior under a desirable state which the component is expected to achieve, which we call function. By classification of the primitives necessary for the interpretation of the behavior in various domains, which we call “domain ontology”, we can capture and represent the function by selection and combination of the primitives. This paper proposes FBRL, a new language for representing behavior and function by combining the primitive we identified. Also we investigate the relation between function and behavior based on the primitives. As the primitives can represent concepts at various levels of abstraction, they will contribute to those tasks which rely on the simulations on the model of the target object, such as diagnosis, design, explanation and so on.     

The MARK III flexible automatic assembly cell

MARK III is a new concept in flexible automatic assembly (FAA) cells and has technically evolved out of the MARK II concept. The MARK III FAA cell is stepwise upgradeable and enables a major reduction in the cost of feeders and programming. It is a hybrid cell, combining automatic and manual assembly. The cell consists of a railtrack-mounted robot and adopts the sub-batch principle. Developed in order to account for the assembly of a vast range of products and variants, the MARK III allows for near-zero changeover times. By incorporating free-coupled manual assembly stations, the stepwise automation of manual operations is supported. These factors permit the automatic assembly of products with an annual volume normally too low to justify automation. Likewise, MARK III offers excellent opportunities for gradual capacity increase. Furthermore, it can account for unpredictable order schemes. The MARK III FAA cell also adopts a new programming and control system (FACE) which enables a drastic reduction in programming costs. This paper describes the evolution of this FAA cell from research to industrial launch.     

Exact Computation of Delaunay and Power Triangulations

In this paper we present a topologically correct and efficient version of the algorithm by Guibas and Stolfi (Algorithmica 7 (1992), pp. 381-413) for the exact computation of Delaunay and power triangulations in two dimensions. The algorithm avoids numerical errors and degeneracies caused by the accumulation of rounding errors in fixed length floating point arithmetic when constructing these triangulations.Most methods for computing Delaunay and power triangulations involve the calculation of two basic primitives: the INCIRCLE test and the CCW orientation test. Both primitives require the computation of the sign of a determinant. The key to our method is the exact computation of this sign and is based on an algorithm for determining the sign of the sum of a finite set of normalized floating point numbers of fixed mantissa length (machine numbers) exactly. The exact computation of the primitives allows the construction of the correct Delaunay and power triangulations. The method has been implemented and tested for the incremental construction of Delaunay and power triangulations. Tests have been conducted for different distributions of points for which non-exact algorithms may encounter difficulties, for example, slightly perturbed points on a grid or on a circle. Experimental results show that the performance of our implementation is comparable with that of a simple implementation of the incremental algorithm in single precision floating point arithmetic. For random distribution of points the exact algorithm is only 4 times slower than the inexact implementation. The algorithm is easy to implement, robust and portable as long as the input data to the algorithm remains exact.     

Labeled point pattern matching by fuzzy relaxation

A method of matching labeled point patterns is described on the basis of a fuzzy relaxation. The method is applicable to labeled point patterns which differ by geometrical transformations, such as translation, rotation and scale change. In this method, the point pairs are considered to be the pattern primitives. The pattern primitives are geometrically transformed in the process of relaxation so as to minimize a measure of mismatch between the primitive pairs. The compatible primitive pairs between the two labeled point patterns are established after only a few iterations of relaxation and the corresponding points are obtained from the primitive pairs. As an example, the method is applied to the matching of constellations.     

A collision problem in OSI standard formal specifications

A collision problem is presented which can occur between two adjacent protocol entities, a user and its local provider. We consider synchronous and asynchronous communication mechanisms at the Service Access Point between the entities; this is normally an implementation choice. It is shown that even if the problem is limited by using a synchronous communication mechanism, instead of an asynchronous one, it still occurs. We suggest that whenever this case is found, the service provided by the protocol entity must be interpreted differently by its user, ignoring some primitives. When an asynchronous communication mechanism is used, care must be taken to verify that those primitives to be ignored cannot be misinterpreted as new primitives; finally, we point out that the protocol specification could be redesigned to handle these collision cases properly.