WSCG '2007: Short Communications Proceedings
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Item Object Description and Decomposition by Symmetry Hierarchies(Václav Skala - UNION Agency, 2007) Huebner, Kai; Skala, VáclavSymmetry is an important feature of visual scene exploration and interpretation. Similarly, hierarchical structures figure an important aspect of symmetry. Visual symmetries describe image regions that might naturally overlap or enclose smaller symmetries. For this reason, objects and scenes can be described in their overall shape as also in their decomposition into more detailed subordinate structures by symmetry hierarchies. Most hierarchical approaches in this area are based on structural, multi-scalar or multi-resolution hierarchies. In this paper, we propose a symmetry-oriented hierarchy with a related, but more cognitive meaning by describing a hierarchy of symmetry itself based on a range-based symmetry detector. We motivate and present an approach for symmetry hierarchy representation and show experiments towards object description and decomposition by symmetry hierarchies.
Item Contributions to Colon Segmentation Without Previous Preparation in Computer Tomography Images(Václav Skala - UNION Agency, 2007) Martinéz, David; Hernandéz, José Tiberio; Florez, Leonardo; Skala, VáclavWe propose a method to segment the lumen of the colon from computed tomography (CT) images. To do so, we use first and second order statistical moments. These moments provide us with a set of descriptors to characterize the homogeneity of regions inside the colon. The algorithm presented in this paper makes use of these values in a prediction-correction exploration process of the colonic region. We show some segmentation results on real patient images that present high nonhomogeneous colonic regions.Item Biped Cartoon Retrieval Using LBG-Algorithm Based State Vector Quantization(Václav Skala - UNION Agency, 2007) Pakdee, Siriprapa; Kanongchaiyos, Pizzanu; Skala, VáclavEfficiency of cartoon motion retrieval depends on indexing method. Keyword based indexing methods for restoring cartoon motion is simple, but sometimes the process of addressing index to the desired motion is not trivial. Although the methods based on clustering clips of motions or keyframes can be used for retrieval automatically, the complexity of time and reliability depend on size of the database. This research proposes a method for biped cartoon motion retrieval using state vectors of keyframes as the motion indexes. The state vectors derived from the input motion is quantized by our enhanced LBG Algorithm to compute the proper number of indexes for the set of input keyframes. The results show that not only the precision and recall of the cartoon motion retrieval is increased accurately but the process for restoring and retrieval is also performed automatically.Item Using Graphics Hardware for Multiple Datasets Visualization(Václav Skala - UNION Agency, 2007) Khanduja, Gaurav; Karki, Bijaya B.; Skala, VáclavWe have applied three graphics hardware-based approaches to support concurrent visualization of multiple sets of volumetric scalar data. They include volume rendering, clipping and isosurface extraction methods, which exploit 3D textures and advanced per pixel operations. These methods are expected to give better interactive frame rates for multiple datasets visualization (MDV) compared to the software-based methods. The rendering time in each case increases nonlinearly with the increasing the number (N) of the datasets being visualized. We can identify three regimes, which can be characterized by different time-N slope value. The first regime with small slope value continues up to about 5 datasets, then the second regime with medium slope value continues up to about 25 datasets, and finally the third regime with much larger slope value continues up to 35 datasets. With volume shading enabled, the rendering time increases on average whereas the transition and maximum N values decrease. We propose the dynamic-resolution approach for increasing the maximum N and frame rates for above MDV techniques.Item Comparative Navigation System for Collaborative Project(Václav Skala - UNION Agency, 2007) Oh, S.; Yeo, W.; Skala, VáclavWe investigated the concepts, strategies, and functions of a 3D virtual design environment for collaborative, real-time architectural design using our 3D comparative navigation system and virtual reality technology. The development of the ‘comparison’ concept has enabled interactive design in real time in a 3D computer environment. Since participants must be able to easily understand the proposed design systems that help them gain this understanding are required. While comparison is an effective way to gain such an understanding, comparing one proposed design to another using existing systems is difficult because the user must operate their viewpoints separately. We therefore created a prototype system that displays different contents simultaneously while controlling the viewpoints automatically to facilitate content comparison. This comparative navigation system facilitates comparison of proposed designs by displaying related parts of the designs automatically. In this paper, we describe the concepts, strategies, and functions of a 3D virtual design environment for collaborative, real-time architectural design that is based on our 3D comparative navigation system and real-time simulation technology. We also evaluate the advantages and disadvantages of using this design environment for collaborative architectural design.Item A Crowd Simulation Using Individual-Knowledge- Merge based Path Construction and Smoothed Particle Hydrodynamics(Václav Skala - UNION Agency, 2007) Tantisiriwat, Weerawat; Sumleeon, Arisara; Kanongchaiyos, Pizzanu; Skala, VáclavPrevious researches on crowd simulation are often based on pre-computed path planning to reduce computational time; however, the pattern of the crowd locomotion is usually unrealistic and the simulation itself is also inflexible. This paper presents a novel technique to model an interactive time crowd simulation by using automatic path construction and Smoothed Particle Hydrodynamics (SPH) in order that each individual can automatically search for the destination without path pre-computation. Two alternating stages approaches are used in our simulation. Firstly, the environment and crowd are set up, and crowd is then moved in accordance with SPH in order to achieve smooth locomotion without fixed pattern. Each agent from a group of crowd can create a map that contains the knowledge of local environment that it gains from perceptions. The local path can be extended and shared corresponding to the new environment or knowledge sharing with other agents. An automatic path determination is done in the next stage by using the potential field. The result from path selection is then used to set the direction of external force in SPH model. By using our method, natural crowd locomotion under a variety of conditions, such as forming and separating lane, obstacles avoidance and escape from unknown area can be represented in interactive time.Item Evaluation of Different Vibration Visualization Modes for Line Tracking(Václav Skala - UNION Agency, 2007) Wang, Yuan; Turner, Martin J.; Hewitt, W. Terry; Skala, VáclavUsing a vibration magnitude model [Wan06] established for the PHANToM haptic device, we have investigated the usability of different modes within a line tracking task. Three key questions were evaluated: (1) does vibration aid in tracking visible lines? (2) Which of the key vibration modes is preferred, either the vibration online mode where the vibration decreases with the distance from the line, or the vibration offline mode where the vibration increases away from the line? (3) And is linear or model constrained mapping more beneficial to the task? The experiment results show that although the vibration mode implemented on visible lines is actually more time-consuming than the mode without vibration, the time ratios spent in high accuracy areas with vibration are enhanced. In comparison with the online vibration, the vibration offline mode provides the more accurate performance to both visible and invisible lines. In certain cases, the vibration magnitude model mapping mode is shown to give superior results, however generally it has the similar usability with the linear mapping mode.Item Associating 6 DoF sensor data to 3D scan view registration(Václav Skala - UNION Agency, 2007) Vergeest, Joris S. M.; Kroes, Thomas; Song, Wolf; Skala, VáclavTo make 3D scanning an attractive tool for incidental or inexperienced users, the process of scan view registration should be avoided or significantly simplified. If a 6 DoF sensor is attached to the object to be scanned, additional data about each of the 3D views can be supplied to the registration software as to provide initial relative placements of pair of views, thus making automatic matching feasible. This releases the user from the tedious manual registration process. A method to apply a 6 DoF device to 3D scanning is in development. To calibrate the sensor to the scanner, the equation of similarity matrices needs to be solved. We verified numerically that this leads to ambiguities if only one sensor-to-scanner association is measured. A method based on a geometric treatment is proposed to achieve an unambiguous association between the two devices. Initial numerical results are presented.Item Feature Extraction and Simplification from colour images based on Colour Image Segmentation and Skeletonization using the Quad-Edge data structure(Václav Skala - UNION Agency, 2007) Sharma, Ojaswa; Mioc, Darka; Anton, François; Skala, VáclavRegion features in colour images are of interest in applications such as mapping, climatology, change detection, medicine, etc. This research work is an attempt to automate the process of extracting feature boundaries from colour images. This process is an attempt to eventually replace manual digitization process by computer assisted boundary detection and conversion to a vector layer in a spatial database. In colour images, various features can be distinguished based on their colour. The features thus extracted as object border can be stored as vector maps in a spatial database after labelling and editing. Here, we present a complete methodology of the boundary extraction and skeletonization process from colour imagery using a colour image segmentation algorithm, a crust extraction algorithm and our new skeleton extraction algorithm. We also present a prototype application for completely automated or semi-automated processing of (satellite) imagery and scanned maps with an application to coastline extraction. Other applications include extraction of fields, clear cuts, clouds, as well as heating or pollution monitoring and dense forest mapping among others.Item Estimating the tumor-breast volume ratio from mammograms(Václav Skala - UNION Agency, 2007) Rodríguez, J.; Linares, P.; Urra, E.; Laya, D.; Saldivia, F.; Reigosa, A.; Skala, VáclavEach year, 182,000 women are diagnosed with breast cancer and 43,300 die, only in America. Currently, more than a million of new cases will be detected around the world. One woman in eight either has or will develop breast cancer in her lifetime. Mammograms are among the best early detection methods. Most women with breast cancer have some type of surgery: Lumpectomy removes only the breast lump and a surrounding margin of normal tissue. Partial or segmental mastectomy or quadrantectomy removes more breast tissue than a lumpectomy (up to one-quarter of the breast). In a total mastectomy the surgeon removes the entire breast, including the nipple. This operation is sometimes used to treat stage 0 breast cancers. For most women with stage I or II breast cancer, breast conservation therapy (lumpectomy and radiation therapy) is as effective as mastectomy. Survival rates of women treated with these 2 approaches are the same. However, breast conservation therapy is not an option for all women with breast cancer. One of the main factors to decide which type of surgery must be used (lumpectomy, quadrantectomy or total mastectomy) is the tumor-breast volume ratio. Unfortunately, because the mammograms are two-dimensional projections of the breast, a process to measure this relationship with the needed accuracy does not exist. So, a correct decision depends on the specialist's ability to imagine the 3D reconstruction from the mammograms. In order to assist the decision making of the surgeon, in this work we have implemented a software application which allows the surgeon to input the mammograms of the patient and obtain a 3D representation of the breast and the tumor. In summary, the software groups a set of tools to segment the breast and tumor from the input mammograms in an interactive way using the intelligent scissors technique, visualize the mammograms in 3D, reconstruct the 3D representation of the breast and tumor and compute a value which represents the volumetric ratio between the breast's reconstruction and the bounding volume of the tumor. This value can be used as a less subjective indicator to decide whether a lumpectomy or quadrantectomy is advisable.Item Fuzzy mathematical morphology and its applications to colour image processing(Václav Skala - UNION Agency, 2007) Popov, Antony T.; Skala, VáclavIn image analysis and pattern recognition fuzzy sets play the role of a good model for segmentation and classifications tasks when the regions and the classes cannot be strictly defined. One of the most widely used fuzzy approaches in image processing is fuzzy mathematical morphology because of the underlaying structure of complete lattices. Thus, mathematical morphology is used mainly in processing of binary or single - valued intensity (grey - scale) images for which a partial ordering, hence a lattice structure, is apparent. However, the problem of morphological image processing of colour images is that it is not naturally clear how to define ordering in a colour space. This paper shows a possible way for solving this problem. It is based on the usage of YCrCb colour space as physically intuitive and easy to compute.Item Automatic Identification of Ambiguous Prostate Capsule Boundary Lines Using Shape Information and Least Squares Curve Fitting Technique(Václav Skala - UNION Agency, 2007) Hussein, Rania; McKenzie, Frederic D.; Skala, VáclavCurrently there are few parameters that are used to compare the efficiency of different methods of cancerous prostate surgical removal. An accurate assessment of the percentage and depth of extra-capsular soft tissue removed with the prostate by the various surgical techniques can help surgeons with determining the appropriateness of different surgical approaches. Additionally, an objective assessment can allow a particular surgeon to compare individual performance against a standard. In order to facilitate 3D reconstruction and objective analysis and thus provide more accurate quantitation results when analyzing specimens, it is essential to automatically identify the capsule boundary that separates the prostate gland tissue from its extra-capsular tissue. However the prostate capsule is sometimes unrecognizable due to the naturally occurring intrusion of muscle and connective tissue into the prostate gland. At these regions where the capsule disappears, its contour can be arbitrarily reconstructed with the generation of a continuing contour line based on the natural shape of the prostate gland. We present an algorithm based on a least squares curve fitting technique that uses a prostate shape equation to merge previously detected capsule parts with the shape equation to produce an approximated curve that represents the prostate capsule. We have tested our algorithms using three shapes on 13 prostate slices that are cut at different locations from the apex and the results are promising.Item An Image Matching Using Critical-Point Filters and Level Set Analysis(Václav Skala - UNION Agency, 2007) Thanasoontornlerk, Kittipong; Kanongchaiyos, Pizzanu; Skala, VáclavCritical-Point Filters (CPFs) are nonlinear filters which preserve intensity and location of each critical point in the image and reduce the resolution without any prior knowledge. Although CPFs can avoid blurred intensity and ambiguous location problem of previous linear filters, its computational cost is still expensive due to its complexity. We propose an enhancement of the CPFs algorithm for image matching using level set analysis. An image is analyzed and transformed to hierarchical level sets of pixel having same intensity. Connectivity of the level sets represents the image contrast invariant features. Between the corresponding level sets of the input images, two pixels are mapped based on their energy and bijectivity conditions. Finally, less computational time with precise mapping is shown in the experimental result.Item Using simplified meshes for crude registration of two partially overlapping range images(Václav Skala - UNION Agency, 2007) Márquez, Mercedes Rocío Gonzales; Shin-Ting, Wu; Skala, VáclavWe present an efficient algorithm for crude registration of two partially overlapping range images. The central focus of our work is how to filter out the wrong pairs efficiently in order to reduce the search space. Motivated by the availability of robust and efficient mesh simplification algorithms, such as the QSLIM software package, which preserve the main characteristics of the surface shape, we propose to find a good initial transformation estimate on the basis of the vertices of simplified meshes, instead of the original dense sets of range data. Promising results, that make the iterative closest point matching procedure converges to a correct final alignment, are provided.Item Virtual Environments and Human-Computer Interaction Anxiety: An Experimental Study(Václav Skala - UNION Agency, 2007) Nassiri, Nasser; Powell, Norman; Moore, David; Skala, VáclavIn a world where interaction is a significant part of everyday life, personal space (PS) – an invisible bubble surrounding human body - is important. This is because PS functions as a comfort zone during interaction, a factor in designing physical environments, and invading such space produces anxiety and discomfort. Little is known, however, about how personal space might operate in virtual environments and what features the interface model of these environments should incorporate in order to reduce the anxiety produced by the invasions of such space in these environments. To begin to address this, we have conducted two experiments concerning personal space invasions (PSI) in collaborative virtual environments (CVE). Results suggest that reactions to PSI in CVE tend to differ in various ways from reactions to PSI in the physical world though some participants experienced anxiety when their avatar personal space was invaded. Recommendations to incorporate some features in the interface model of these environments are presented.Item Physically Realistic Interface for a user inside VR(Václav Skala - UNION Agency, 2007) Hashimoto, Masahide; Miyamoto, Kenji; Skala, VáclavInteraction between a user inside a virtual space and virtual objects is described. Incorporating a user's live image into a virtual space enables him/her to exist in the same place as objects and to interact with them. There are, however, the lack of guideline to design interaction style makes users confused about how to use it. This article proposes a common implementation framework that forces the interaction to be physically realistic. As a result, the look & feel of interaction becomes uniform. In a ball game application and virtual electronic controllers made by this framework, a user manipulated/played in the same way as those in the real world. This framework could provide novice-friendly or hands-free interface ubiquitous around public or daily places.Item Measuring and segmentation in CT data using deformable models(Václav Skala - UNION Agency, 2007) Krajíček, Václav; Pelikán, Josef; Horák, Martin; Skala, VáclavWe investigated the concepts, strategies, and functions of a 3D virtual design environment for collaborative, real-time architectural design using our 3D comparative navigation system and virtual reality technology. The development of the ‘comparison’ concept has enabled interactive design in real time in a 3D computer environment. Since participants must be able to easily understand the proposed design systems that help them gain this understanding are required. While comparison is an effective way to gain such an understanding, comparing one proposed design to another using existing systems is difficult because the user must operate their viewpoints separately. We therefore created a prototype system that displays different contents simultaneously while controlling the viewpoints automatically to facilitate content comparison. This comparative navigation system facilitates comparison of proposed designs by displaying related parts of the designs automatically. In this paper, we describe the concepts, strategies, and functions of a 3D virtual design environment for collaborative, real-time architectural design that is based on our 3D comparative navigation system and real-time simulation technology. We also evaluate the advantages and disadvantages of using this design environment for collaborative architectural design.Item Occlusion detection and surface completion in 3D reconstruction of man-made environments(Václav Skala - UNION Agency, 2007) Pospíšilová, Radka; Skala, VáclavThis paper presents the methods for the quality improvement of the man-made environments reconstruction. The 3D model is created from the set of images without any user interaction. Some generic assumptions about the scene geometry are used; for example continuity of surfaces, piecewise planar scene or frequent parallelism and orthogonality between planes and lines. This information is employed to reduce the ambiguity of the 3D reconstruction and for the occlusion recovery. Method for the completion of the occluded surfaces is presented. First, the position of missing parts of the scene is detected and then the gaps are filled by the most suitable shape.Item Viewpoint Selection Based on Fechner Type Information Quantities for 3D Objects(Václav Skala - UNION Agency, 2007) Oba, Satoshi; Ikai, Takeo; Aoki, Shigeki; Yamashita, Takuya; Izumi, Masao; Fukunaga, Kunio; Skala, VáclavThis paper proposes several algorithms for selecting viewpoints, based on information quantities, which provide representative views expressing a whole feature of 3D object. By defining a novel information quantity of Fechner type based on Fechner’s law in psychophysics, we introduce shape information quantities depend on an area of face and depend on a length and sharpness of edge line in a polyhedral object. We then define viewpoint information quantities of several types obtained by summing up shape information quantities of the visible surface form a viewpoint. Representative views are obtained from viewpoints at local maximum of the viewpoint information quantity of each type. The face type and the edge type of algorithms are derived that compute viewpoint information quantities obtained from all visible faces and all visible edge lines respectively. Experimental results and estimation on polyhedral objects and triangular mesh representations of curved objects are presented.Item Rapid Development of Virtual Environments: A systematic approach for interactive design of 3D graphics(Václav Skala - UNION Agency, 2007) Qian, Xuelei; Zhao, Zhengxu; Thorn, Richard; Skala, VáclavIt has long been a bottleneck for VE popularity that the development of VE normally acquires heavy time, labour and monetary investment. Although so-called high-level, abstracted graphical libraries which have been delivered by third parties based on industrial standard like OpenGL speed up the VE development to certain extent, the involved engineering process which largely relies on the system computing approach is by all means not developer-oriented but application-specific, thus it remains technically difficult and expensive to create VE application from scratch. This research attempts to propose an ultimate solution for VE rapid development by exploring the boundary between system programming, interpretative computing, interfaces wrapping, abstracted scene-graph libraries, grouping and database technology. The convergence of ideas from these technological fields has formed a systematic approach by which developers are encouraged to design and implement 3D interactive graphics via making necessary reconfiguration to both graphical content and rendering context take place at system runtime. The whole development cycle of VE application can be further accelerated by using similar existing drawings from the database as reconfigurable VE templates. In this way, the developers can avoid creating graphical application completely from scratch by making runtime changes to retrieved VE template in terms of its rendered graphics, user interfaces and related functional modules.
