Search

In this paper, we propose a new human computer interface which offers an alternative to traditional mouse and direct manipulation interfaces. This interface enables a user to specify commands and additional parameters by drawing single intuitive gestures with his finger. Most gesture-based interfaces researched so far have needed a mouse or stylus pen as a gesture input device. However, we believe that the idea of making gestures with a human finger appeals more to not only experienced users but also novice users who are usually not accustomed to using computer devices. This paper describes the finger mouse system (FMS) and finger gesture recognition system(FGRS). FMS emulates the functions of a mouse by capturing the image of a hand and analyzing its motion and shape. FGRS provides the user with the capabilities of command input and direct manipulation by recognizing the gesture input by FMS. We utilized Kalman filter-based tracking and syntactic pattern recognition techniques for implementing FMS and FGRS. In addition, we introduce an example drawing program in order to demonstrate the practicality of our approach.

New developments in 3-D volume acquisitions are creating a rapidly increasing demand for integrating multimodality 3-D visualization. In order to accomplish routine clinical multimodality visualization, many issues have to be dealt with, such as techniques for accurate spatial registration, integrated representation, suitable graphical user interfaces, and obtaining adequate rendering speeds. The aim of this experience paper is 2-fold. First, it presents various results from our research on multimodality visualization/registration. Second, this paper explicitly addresses practical problems and findings related to software development and multimodality registration/visualization. We hope that this will give colleagues a better understanding in some of these issues based on our experience, including notably our mistakes.

This paper develops a sophisticated approach to a method for fitting of complex 3-D shapes to unsegmented sets of data. The approach features dynamic models consisting of parametrically defined solid primitives (such as superquadrics), global geometric transformations, global deformations and local finite element deformations. Our technique deals with a deformable model consisting of multiple primitives (parts) that can be used to represent even more complex shapes than are common in the natural world. The deformable model is extended to the case of unsegmented data, incorporating an extended version of a fuzzy clustering technique. The image or range data are transformed into forces acting on the model that deform and conform to the given data set while continually synthesizing nonrigid motion. An adaptive procedure updates a damping factor in accordance with the largest possible step in an implemented iteration process. We demonstrate the fitting process in experiments involving the extraction of the shape of the mouse embryo's organs from microscopic sections.

In the framework of Visualization in Scientific Computing (ViSC) the definition of reference models appears to be an especially promising research area. In this paper we propose a unified approach to the analysis of reference models based on keyword classification. We analyze several models representing either visualization systems or complex computational and visual processes. We propose grouping the reference models in two sets called Reference Models in Scientific Visualization and Reference Models of Visual Computational Simulations respectively. For each of these two sets we present a general overview of reference models belonging to, we identify the main concepts and keywords characterizing the reference model definitions, and we present the result characterization organized in lists. We propose definitions of the structure of each of the reference model and representative keyword sets. To characterize specific models, and underline either their commonalties or distinctions, we label for instance two- or three-dimensional and one- or multilevel structures. We start to develop a comparative analysis of separate approaches and we identify elements significant for further advances in reference model design.

Space deformations or free-form deformations techniques are a powerful tool to manipulate and to animate objects. Various extensions of these techniques allow a user to intuitively deform objects, but none of these propose a solution to preserve the volume of objects throughout the deformation. This paper introduces a new method to deform an object, its volume being preserved. Our method is based on the space deformation model called DOGME. We use a distinctive feature of DOGME to solve the problem of volume preservation. Polyhedral objects which are currently used in geometric modeling are considered and we obtain excellent results in a fully intuitive and interactive environment.

In this paper, a new method for computing the intersection of a ray and a NURBS surface is presented. The method is based on Newton iteration for a system of nonlinear equations, but its convergence is accelerated by using the polynomial extrapolation. Additionally, a ray is defined to be the intersection of two planes, which are usually non-orthogonal, so that theoperations are significantly reduced. A trapezoid prism is adopted for the bounding box enclosing the patch as tightly as possible. It can be used both for getting a good start point for the Newton iteration and for efficiently detecting whether a ray intersects a patch. The method proposed for speeding up ray tracing NURBS surfaces can reduce both the iteration steps and arithmetic operations, thus much CPU time is saved. The new method is faster than the previous methods for which published performance data allow reliable comparison. The acceleration techniques with extrapolation presented for solution to a system of nonlinear equations can also be used to speed up tracing the intersection of two parametric surfaces as well as others that need Newton iteration.

Although there is a great deal of work on facial animation, there is not much research on the effect of jaw motion on the movement of the face. The complex nature of the jaw bones makes it difficult to implement all the motions the jaw can do. The human jaw has two widely separated identical joints behaving like a single joint. Widely separated joints of the mandible (lower jaw bone) allow it to translate in any direction and/or rotate about any axis in three-dimensional space although its movements are somewhat restricted by physical constraints and patterns of muscle activity. A simplified jaw model which covers the major movements of the jaw is proposed in this paper. The lower jaw in the model can rotate around the axis connecting the two ends of the jaw and make small translational motions in any direction in 3-D space. The face is modeled as a two layer model which is attached to the jaw. The inner layer of the face moves kinematically as dictated by the jaw. The outer layer moves with the effect of the springs connecting it to the inner layer. The motion of the outer layer is calculated using spring-mass equations. Eating and chewing actions are simulated as applications of the model.

Sweeping is a very important, powerful, and widespread method in geometric modelling. In this paper, we consider only sweep surfaces, generated by sweeping one curve (cross-section) along the other curve (trajectory), and their existing construction methods: the Frenet frame method, the discrete approach, the offset method, and the projection technique. All these methods are extended so that they now include non-homogeneous scaling and twisting of the cross-section, which enable the generation of complex twisted-profiled sweep surfaces.

In this paper we generalize the method of sweeping, which may be used for both object representation and object visualization, to objects in E4. The generalized sweeping method involves a trajectory in E4, and a three-dimensional cross-section orthogonal to the trajectory. Three alternatives are considered for specifying the relationship between the trajectory and the cross-section, namely the Frenet frame, modified Frenet frames, and the standard viewing-reference coordinate (VRC) frame, where each of these is generalized to the case of four dimensions. We have implemented the method using the four-dimensional VRC frame, and the method is illustrated here by means of two examples involving visualization of objects embedded in E4.

In this paper we present a 3-D model with physical properties which simplifies the analysis and the synthesis of deformable faces and solids. Our model presents three relevant particularities. First, it describes the external envelope of faces with 1-D finite elements assembled with a new 3-connected mesh topology. Second, the mesh deformations are analysed with a modal analysis. Because our model associates these two particularities, the number of rigid modes given by the modal analysis is equal to the number of 1-D finite elements, which is also the half of the number of Degrees of Freedom (DOF). This number of rigid modes is a basic characteristic of our model. The second half of modes constitutes the nonrigid modes. Third, we use these rigid modes and the first nonrigid mode to synthesize a mean face named a photo-fit identikit or class, around which we synthesize face varieties by action on secondary nonrigid modes. Our physical 3-D model allows compression of face data structures because a greater number of secondary nonrigid modes can be suppressed to define a class or its varieties, and because the synthesis of varieties does not need more information storage than their classes. Our physical 3-D model allows classification of face data structures because we can associate an objective measure to each synthesized face. We can measure the deformation between a variety and its photo-fit identikit.

Today's software systems for medical visualization still suffer from a shortage of practical applications due to their lack of usability with respect to a large variety of users with different computer-skills and experiences. Furthermore, progress is often hampered by the lack of adequate software tools that allow research ideas to be rapidly accomplished, evaluated, and brought into routine. We developed an integrated software environment that is distinct because it, on the one hand, provides an application-builder toolbox for medical diagnosis and therapy. And, on the other hand, it allows for the development, integration, and user-centered evaluation of existing and new interaction techniques in 2-D, 3-D, and Virtual Reality (VR). The environment's interaction support is based on communicating application objects that employ a sophisticated message-based inter-object communication. In addition, the system contains a component for user-adapted interaction and system support. The system has been used for several clinical applications which are briefly described at the end of this paper.

In this paper, we present a technique for simulating different facial gestures and speech. The distinguishing features of this work are 2-fold. First, we adopt a four-level hierarchical, non-uniform rational B-spline (NURBS) based face model. The use of NURBS surface representation of the face has the advantages of increased smoothness and ease of reshape over other forms of geometric representation. Second, the mouth movement animation and sound production in speech are phoneme based and an English text to phoneme parser is used to translate any English text in speech into its phoneme equivalent. As phoneme is the basic unit of mouth movement and sound production, a phoneme based approach of speech animation resembles actual speech and allows arbitrary English text rather than a restricted set of tokens be spoken. A Facial Action Coding System is also adopted to control the modification of the face model as it describes the basis of facial expression. Further, a user interface is developed which allows the user to edit interactively or load in a text script describing the animation sequence in terms of facial gesture names and English text. The system parses the English text in the text script to phoneme strings. The animation sequence described by the ccript can then be generated and played back in a flexible way.

This paper presents an intuitive method to simulate architectural space and objects by using gesture modeling. This method applies hand movements to retrieve data and generate objects under circumstances allowing larger tolerance. Communication between gesture (actor) and computer (listener) is conducted with a set of basic components like gestures, regulations, and interfaces. The components are used as theoretical models to assist gesture-aided 3-D modeling. Gesture is analyzed by both surface and deep structures in syntactic structure. At the outset, persons of different backgrounds were requested to model a virtual building. Several basic gesture types were concluded based on experiment categorization. The test result was used to build a theoretical model and conduct subsequent simulation. A 3-D digitizer associated with software is applied as a communication interface between user and computer. Gestures are simulated by moving a stylus held by one hand.

This paper presents a new vector interpolation method for Phong shading, referred to as binary interpolation. It can calculate the reflection model by a scalar method. A pre-defined table is used to convert scan lines into segments, each of which is a power of two in length. Then binary interpolation is carried out in each segment. The new method has been tested in two situations; firstly with various sizes of right angled triangles, secondly with the Utah teapot. The results show that, excluding plot to screen time, binary interpolation can decrease the calculation time for a reflection model by about 20%.

Image-guided, computer-assisted surgery systems require a common reference between the preoperative image data and the corresponding patient pathology. Therefore, the problem of an accurate and reliable 3-D patient registration and referencing has to be solved. Considering that during image data acquisition patient misalignment and movement can arise in three dimensions, an automatic image registration method must be based on a three-dimensional approach. The method presented in this paper provides accurate 3-D patient registration for correction of these movement errors during data acquisition and active patient referencing to update the position of the head during surgery. Experimental data concerning the accuracy of repeated positionings of our patient registration and reference system demonstrated a high degree of accuracy with mean spatial errors of 0.82 mm ± 0.31 mm in a plastic skull and 1.56 ± 0.76 mm in patients, respectively. Results suggest that non-invasive 3-D patient registration for image-guided surgery may be a precise and useful method for computer-assisted identification of anatomical structures.

In this short paper, we illustrate the emergence of complex structures from a simple model of life at the “edge of chaos”. The visualization of the generated patterns provides a good way for understanding the self-organized critical dynamics of the model.