Tycho crater is the most prominent crater of Copernican era. In this paper, the spatial and temporal features of the microwave thermal emission (MTE) at Tycho area are studied with the microwave sounder (CELMS) data combined with TiO2abundance, surface slope and roughness, rock abundance data of lunar regolith. The results indicate that MTE at the south part of Tycho crater (Region A) is strongly affected by the surface temperature, and the temperature difference between the exterior and interior of the lunar regolith layer is fairly large. While MTE at the north part of Tycho crater floor (Region B) is weakly affected by the surface temperature, and the temperature difference between the exterior and interior is rather small. Moreover, the vertical structure of the lunar regolith at the east part of Region B is different from that at the west. Furthermore, the radiation here reaches the thermal equilibrium state after 3 A.M. in the morning, which is of essential significance to study the thermal structure characteristic of the Moon. The lunar regolith at the ejecta blanket is similar to that at Region B, while its thermal storage capacity is much higher than that of other places. The correlation analysis presents that the surface roughness and rock abundance have the largest impact on the MTE, followed by surface slope and TiO2abundance.

As Mare Orientale is the youngest and best preserved multiring impact basin on the Moon, it is of essential importance to study its composition and structure for current Moon research. In this paper, the CELMS data from Chang'E-2 satellite are employed to reveal the microwave thermal emission features of the Mare Orientale. The results indicate that the regions with high TBand high TBdifference are strongly influenced by FTA, but FTA is not the only factor. Moreover, the lunar regolith structure is not even at the mare basin. Furthermore, there exist abundant abnormal TBand high TBdifference regions which could hardly be explained by the current Moon research.

Reflection symmetry detection receives increasing attentions in recent years. The state-of-the-art algorithms mainly use the matching of intensity-based features (such as the SIFT) within a single image to find symmetry axes. This paper proposes a novel approach by establishing the correspondence of locally affine invariant edge-based features, which are superior to the intensity based in the aspects that it is insensitive to illumination variations, and applicable to textureless objects. The locally affine invariance is achieved by simple linear algebra for efficient and robust computations, making the algorithm suitable for detections under object distortions like perspective projection. Commonly used edge detectors and a voting process are, respectively, used before and after the edge description and matching steps to form a complete reflection detection pipeline. Experiments are performed using synthetic and real-world images with both multiple and single reflection symmetry axis. The test results are compared with existing algorithms to validate the proposed method.

We propose robust affine-invariant contour descriptor and measure for shape matching under nonlinear deformations. The descriptor is formed by orthonormal configuration matrix of local contour. The geodesic distance on Grassmann manifold is used to measure similarities of shapes under locally affine transformations, which can approximate complex deformations like articulations. A rigorous perturbation analysis proves that condition numbers of configuration matrices are critical for robustness. Then a method to improve matching stability using the condition numbers is deduced. Commonly used contour matchers, e.g., dynamical programming and others, are all applicable to the descriptor to obtain satisfied matching. Experimental evaluations are given using both synthetic and real-world images.

The Chang'e orbiter has successfully operated for more than 1 year. The exploration data sent back by Chang'e has been distributed to registered research institutes and universities after the pre-processing in National Astronomical Observatories of China (NAOC). This talk will introduce the processing and visualization of Chang'e-1 Lunar Exploration Data in Macau University of Science and Technology collaboratively with NAOC, CSSAR and Tsinghua University in the past few months. In this talk, the scientific objectives and its related data of Chang'e-1 will be firstly introduced. In order to study the topology of Lunar surface, the enhancement and automatic seamless stitching of the images from CCD camera will be shown and the data processing and its visualization of the laser altimeter will be discussed, then, followed by the comparison with the results of other countries. For the purpose to analyze the abundance of different elements and its distribution on lunar surface, the analysis of γray spectrum and the distribution of Thorium will be presented. To probe the space environment in the vicinity of the moon, the preliminary results for visualization of measurement data of sonar wind will also be shown. At last, future works will be discussed.

This paper presents a new concept of texture image method for displaying divergent-free vector field on surfaces, sine modulated potential (SMP) map. A scalar potential for such vector field is first defined. Field vectors are then mapped to a grayscale image through its scalar potential modulated with a sine function. The image visualizes a soft appearance of flux tubes instead of flux lines, whose orientation and width reflect the direction and amplitude of field vectors respectively. Animated SMP images can identify the exact "flow" direction inside each flux tube for the vector field at a specific moment, which is often missed in other visualization techniques. SMP images can also be animated for visualization of time-varying field, in which the variation of the field in space and the variation with time can be revealed simultaneously.

A new image synthesis method, which is called foreground-distortion, is presented in this paper. In this method, foreground extraction procedure is used to get the interesting part from the texture sample, and many-knot spline interpolation distortion method is used to generate similar texture foregrounds. These similar texture foregrounds are extracted and copied onto a larger background image and a new output image will be synthesized. Compared with other methods, this method is simple and fast, texture seam problem can be avoided and, fewer texture samples even only one will be used to generate a large synthesized image. The sheltering effect between texture foregrounds can be implemented in this method while the texture foregrounds are overlapped. The results for synthesizing natural scenes and random textures are shown. We also demonstrate how this method can be used to interactively merge different images to generate new pictures.

Demonstrations play a major role in education process. Although many specimens are readily available, particularly in medicine and biology, demonstrations are commonly performed by showing these static specimens to medical or biological students. Interactive demonstrations can significantly impacts learning. An interactive system for visualizing 3D human organ models can fulfil this need. In this paper, we present techniques to realize such a system which can let the user select and view one or several major organ models extracted from segmented visible human dataset interactively through a simple graphical user interface. The stereoscopic views of these organ models are also achieved with this system running on a PC-based stereo-ready system. In our system, the marching cubes algorithm is used but new implementation we proposed to greatly improve both the speed and quality of surface rendering results is performed. This new implementation can generate the marching cubes cases on-the-fly within the surface extraction process of the models by considering the relationship of the vertices, borders, and surfaces of each voxel. We also describe a new method for specifying the normals for the extracted triangles without the need of physical information (such as intensity values stored in a medical computed tomography (CT) dataset) stored in the voxels. These normals will be used for lighting the extracted models later. Furthermore, a memory arrangement scheme is designed to enhance the usability of the system.

This paper introduces the research project of robot assisted minimally invasive neurosurgery. Using visualization technology, the system reconstructs and displays the 3D model of the patient's inner structure in the computer. Thus the surgeons can plan the surgery on the model in the computer. Marker registration is used to create the mapping between the patient's head and the 3D-brain model. Robot arm is used as a navigator to direct the surgery planning and as an instrument platform to assist surgeons to accomplish the operation. The results of the clinical application are given to show that the robotic system is effective.

The level-of-detail modeling method is an effective approach for the interactive visualization of complex models. In this paper, we propose a hierarchical tree structure based on the fractal dimension to organize a 3D terrain mesh model and to realize view-dependent continuous level-of-detail rendering of terrain data with a restricted quadtree triangulation method. The total algorithm can be divided into two stages: pre-processing and rendering. In pre-processing, it builds an adaptive hierarchical structure by considering the flatness of the terrain surface evaluated by the fractal dimension. Then it can generate a triangular approximation mesh by dynamically determining preserved data points according to the view-related parameters and performing a restricted quadtree triangulation. Some experiments demonstrate that it is simple and efficient and can be used to support the interactive dynamic rendering of terrain models.

A new kind of NURBS representation for periodic curves is introduced. The method for periodic curves is extended to derive a compact and symmetric representation of the sphere or the ellipsoid using a piecewise bi-quadratic NURBS surface with only eight distinct control vertices.

A fast algorithm for large scale scattered data approximation is described. The algorithm exploits a coarse-to-fine hierarchical control lattice to fit the scattered data. In this algorithm, the refinement process is only located in the regions where the error between the scattered data and the resulting surface is greater than a specified tolerance. A recursive algorithm is used to find these regions. In order to ensure the C/sup 2/-continuity of the resulting surfaces, we introduce an additional method to get the boundary control points around the subcontrol lattice. Experimental results are included to show that this method can approximate large scale scattered data sets quickly.

A new stick text segmentation method based on sub connected area analysis is introduced in this paper. The foundation of this method is the sub connected area representation of a text image that can represent all connected areas in an image efficiently. This method consists mainly of four steps: sub connected area classification; finding the initial boundary following point; finding the optimal segmentation point by boundary tracing; and text segmentation. This method is similar to the boundary analysis method but is more efficient.

Direct volume rendering techniques use semi-transparency to visualize much more important features in the three-dimensional scalar sample volumes than isosurface rendering methods. However, they are computationally expensive and far from interactive manipulation. In fact, on the base of the boundary representation scheme for the volumetric data, the 3D spatial coherence can be fully exploited to drastically reduce the rendering time and the memory space for arbitrary viewing orientation. A PC-based rendering algorithm using the boundary scheme is proposed in this paper, which produces results visually similar to the volume rendering techniques, but speedups at least an order of magnitude. Examples from medical CT studies are given in contrast to the results from ray casting method both in image quality and in processing time.

In this paper, a boundary element method and a finite element method with the static condensation technique are respectively applied to real-time animation of deformable objects. First, a finite element model in conjunction with the static condensation technique for eliminating internal nodes of the deformable object is introduced to simulate in real time deformation of the objects. Then, a Boundary Element Method (BEM) is given to accelerate solution to the dynamic deformation problem and to simplify data preparation. Finally, the above methods have respectively been applied to the anatomical or surgical simulation. A pituitary model in the human brain, which is reconstructed from a set of anatomical sections, is selected to be a deformable object under the action of a virtual tool such as scalpel or probe. It produces fair graphic realism and high speed performance. The results show that the BEM not only has less computational expense than the FEM, but also can be convenient to combine with the 3D reconstruction and surface modeling as it enables the reduction of the dimensionality of the problem by one and simplifies data preparation.

A method based on connected area detection is developed to segment and recognize dimension texts in engineering drawings. First we propose an effective algorithm to find all connected areas from drawing image. Then we use size criteria to find out character candidates from all connected areas and use collinear criteria to group separate character candidates into text strings. Finally we analyze text strings according to text patterns summarized from dimension texts and give out the recognition result.

The second international conference on Computer Graphics around the Pacific area-Pacific Graphics '94-was held in August 1994 at Beijing, China.In order to share the contributions from the authors in this conference and to improve the mutual communication among researchers and developers with common interests, four papers have been selected from this conference for publication in this special issue.In recent years, the animation of the human body has been a hot topic for research.The paper 'A Dynamic Wrinkle Model in Facial Animation and Skin Ageing' describes a dynamic model to simulate expressive wrinkles in 3D facial animation and skin ageing.In this model, action units in the facial action coding system are used to define facial expressions, and the skin is specified as a nonlinear and inelastic material.The system produces distinctive expressive wrinkles corresponding to different faces with the dynamic model.Generating an image for high qyality with volume rendering is extremely expensive and far from interactive.The time complexity of the volume rendering is determined by the number of cells.In the paper 'Subvolume Projection: A Full Exploitation of Function Coherence for Volume Rendering', the spatial coherence of a function distribution is fully exploited by partitioning a volume into a number of subvolumes.Each subvolume can be considered as containing a single material and treated as the smallest unit instead of cells in the processing.Theoretical analysis and the experimental results show that the new approach improves image quality and reduces rendering time.Fractal geometry provides an outstanding mathematical tool for simulating natural phenomena.However, the recursive process of stochastic modelling in generating random fractals results in difficult problems in the rendering.In the paper on 'A Radiosity Solution for Random Fractal Surfaces', a radiosity solution for rendering random fractals is given.The recursive process of fractal generation is naturally incorporated into the progressive refinement procedure of radiosity solution.Some examples show that this method is efficient.In the paper 'Modelling Radiative Properties of Light Sources and Surfaces', a

Abstract Direct volume rendering techniques present a huge potential for displaying a great amount of information in 3D data sets within one image. However, generating such an image is extremely expensive, and rendering for high quality pictures is far from interactive. Traditional volume rendering approaches are based on a cell‐by‐cell model. They consider cells as the smallest manipulation object. The time complexity of the volume rendering is determined by the number of cells, and the image quality, to some extent, is affected by the cell tessellation of volumes. Many scientists and technicians rarely venture to research the exploitation of coherence of function distribution over scalar fields through partition of data volumes. This paper proposes a new volume rendering approach: subvolume projection. It not only exploits the spatial coherence of cells but employs fully the spatial coherence of function distribution to partition a volume into a number of subvolumes, so that the function varies slowly over each subvolume. Each newly generated subvolume can be considered as containing a single material and treated as the smallest unit instead of cells in the processing. Based on the subdivision of the volume, this paper discusses the calculation of intensity contributed by the subvolumes in detail. Theoretical analysis and a variety of experimental results show that the new approach improves image quality and reduces rendering time period. (Usually the new algorithm is three to four times faster than the traditional volume rendering algorithms).

An algorithm for recognizing and understanding dimensions in engineering drawings is presented. The dimensions are classified into 27 patterns and 48 subpatterns. The concept and algorithm of arrowhead-match is presented. A DFA is used to detect and recognize dimensions and rectify their rationality.>

It is essential and pressing to improve reliability of Boolean operations in geometric modelling systems. The Boolean operations in commercial systems now available are not reliable enough because of numerical calculation errors. Numerical calculation errors hinder us from determining set membership classifications exactly. Some classifications are ambiguous because they are dependent on adopted computing tolerance. Thereby interrelated classifications may conflict with each other and it is very difficult to get correct results of Boolean operations In many cases. We introduce a reliable Boolean operation algorithm which solves the conflicts among interrelated classifications before implementation of Boolean operation by use of reasoning technique. The algorithm has replaced the modelling module of the geometric modelling system GENS 2.0 to form a new system GENS 2.1 on Apollo and Sun workstations. According to tests and compared with Geomod 3.9 and I/ENS, GENS 2.1 is much more reliable.

Conversion algorithms between different object representations have become Increasingly important In soIid modeling system. In this paper, an algorithm for converting boundary representation of 3D object to octree structure is presented. This algorithm Is based on the transformation of Cartesian coordinates of voxels in the object universe to octant addresses or to node addresses of octree. The surface coherence, edge coherence, voxel coherence are used to speed up the transformation. In order to save memory space, Iinear octree Is used and the Intermediate resulting octant addresses are condensed as early as possible. The resolution of octree structure may also be controled by defining the number of levels of octree. This Is the bottom-up algorithm for converting boundary representation of 3D object to octree structure.

Abstract An algorithm for automatic reconstruction of 3D objects from their orthographic projections is presented in this paper. It makes some improvements to, and complements the, Wesley‐Markowsky algorithm, which is a typical hierarchical reconstruction algorithm limited to polyhedral objects, and extracts the idea of pattern recognition expressed in the Aldefeld algorithm. It is shown in theory by analysis and in practice by implementation that the proposed algorithm successfully rejected pathological cases and found all solutions with the same set of orthographic views. Compared with the existing algorithms presented in references, this algorithm covers some more complex cases of objects incorporating cylinders.