An interactive triangle-based ODF glyph rendering for high angular resolution diffusion imaging [preprint |supplemental video]
Authors: Daniel Xavier Silva, Raphael Voltoline Ramos and Wu, Shin-Ting
Published in Special Section on SIBGRAPI 2023 of Computers & Graphics
Abstract
Diffusion magnetic resonance imaging quantifies the diffusion of water molecules. It is unique in showing white matter fiber structures and connectivity in-vivo, relying on the fact that the water molecules' displacements are more significant along with the fiber orientation than in other directions due to biological barriers. High angular resolution diffusion imaging (HARDI) acquisition enables the differentiation of multiple fiber signals passing through a voxel. Advanced methods for processing diffusion data were developed to synthesize the HARDI data of each voxel into an orientation distribution function (ODF) that relates each direction sample to its probability of water diffusion. Visualizing ODFs through glyphs helps gain insight into the local structure of the brain white matter. Because of the high dimensionality of the data, interactive glyph exploration remains a challenge for a volume containing millions of voxels. This work presents a 3D triangle-based multi-resolution rendering scheme for the ODF glyph. We explored data properties and GPU features to make the triangle-based rendering interactive. Linear performance relative to some fixed-resolution rendered glyphs was assessed using NVIDIA® Nsight Visual Studio™. A control volume, available in the Retest dataset of the WU-Minn Human Connectome Project, was used to assess the effectiveness of interactive 3D visualization over a multiplanar and curvilinear reformatted volume of ODF glyphs in voxels with multiple fibers, namely the triple crossing at the centrum semiovale, the fanning at the corona radiata, and the crossing of the cingulum and corpus callosum fiber bundles.

Interactive DTI-Based Constrained Tractography using OpenGL Pipeline [pdf |supplemental video]
Authors: Wu, Shin - Ting, Raphael Voltoline Ramos and Rodrigo Lacerda Benites
Published in Proceedings of SIBGRAPI 2023 - 36TH Conference on Graphics, Patterns and Images
Abstract
This paper addresses the limitations of the DTI-based tracking algorithms commonly applied in routine clinical practice. Interactive tracking and rendering algorithms are presented using the OpenGL pipeline, allowing experts to explore, adjust, interpret, and validate the reconstructed pathways. The key features of our algorithms are fiber tracking preprocessing and separation of tracking and rendering stages.

Interactive Individualized Neuroanatomy Labeling for Neuroanatomy Teaching [online]
Authors: Felippe T. Angelo, Raphael Voltoline, Giuliano R. Gonçalves and Shin-Ting Wu
Published in Journal of WSCG (Vol. 29, No. 1--2, ISSN 1213-6972), selected paper from the works presented at WSCG 2021
Abstract
As the imaging technology and the understanding of neurological disease improve, a solid understanding of neuroanatomy has become increasingly relevant. Neuroanatomy teaching includes the practice of cadaveric dissection and neuroanatomy atlases consisting of images of a brain with its labeled structures. However, the natural inter-individual neuroanatomical variability cannot be taken into account. This work addresses the individual gross neuroanatomy atlas that could enrich medical students' experiences with various individual variations in anatomical landmarks and their spatial relationships. We propose to deform the CerebrA cortical atlas into the individual anatomical magnetic resonance imaging data to increase students' opportunity to contact normal neuroanatomical variations in the early stages of studies. Besides, we include interactive queries on the labels/names of neuroanatomical structures from an individual neuroanatomical atlas in a 3D space. An implementation on top of SimpleITK library and VMTK-Neuro software is presented. We generated a series of surface and internal neuroanatomy maps from 16 test volumes to attest to the potential of the proposed technique in brain labeling. For the age group between 10 to 75, there is evidence that the superficial cortical labeling is accurate with the visual assessment of the degree of concordance between the neuroanatomical and label boundaries.

Multimodal visualization of complementary color-coded FA map and tensor glyphs for interactive tractography ROI seeding [online]
Authors: Raphael Voltoline and Shin-Ting Wu
Published in Computers & Graphics
Abstract
Fiber tractography is still unique in providing detailed imaging of white matter fiber bundles and connectivity between different brain regions. For finding specific fiber bundles, the most applied technique is tracking fibers from the seeds in a region of interest (ROI) within a diffusion tensor imaging (DTI) volume, or the limitation of tracking results to the ROI. Color-encoded fractional anisotropy (FA) map derived from DTI data, neuroanatomical atlas, and anatomical T1-weighted magnetic resonance imaging (MRI) data have been proposed as complementary data to improve the placement of an ROI. Mental mapping of colors in color-encoded FA map to directions requires a cognitive process. This paper addresses the fusion of shape with color to make the ROI drawing more a perceptual rather than a cognitive task. We propose the rendering of diffusion tensors as superquadric glyphs (shape) superimposed over the standard practice consisting of a color-encoded FA map (color) co-registered to a T1-weighted MRI image (anatomical constraint). A novel object-space algorithm that can efficiently render diffusion tensor glyphs is presented. A strategy for distributing the GPU hardware workload was devised to maximize its occupancy and reduce its stall. Implementations with a compute shader, and a geometry shader are detailed comparatively. We show that our proposal outperforms other rendering solutions. Preliminary quantitative comparisons of the nerve fibers reconstructed by interactive seeding strategies with and without the glyphs suggest that the first approach is more accurate in conveying directional information.

Accurate Image-guided (Re)Placement of NIRS Probes [online]
Authors: Shin-Ting Wu, José Angel Iván Rubianes Silva, Sérgio Luiz Novi, Nicholas Gabriel S.R. de Souza, Edwin Johan Forero, Rickson C. Mesquita
Published in Computer Methods and Programs in Biomedicine
Abstract
Background and Objective: Functional near-infrared spectroscopy (fNIRS) has become an attractive choice to neuroscience because of its high temporal resolution, ease of use, non-invasiveness, and affordability. With the advent of wearable fNIRS technology, on-the-spot studies of brain function have become viable. However, the lack of within-subject reproducibility is one of the barriers to the full acceptability of fNIRS. To support the validation of the claim that within-subject reproducibility of fNIRS could benefit from accurate anatomical information, we present in this paper a method to develop an image-based system that improves the placement of the sensors on the scalp at interactive rates.
Methods: The proposed solution consists of an electromagnetic digitizer and an interactive visualization system that allows monitoring the movements of the digitizer on a real head with respect to the underlying cerebral cortical structures. GPU-based volume raycasting rendering is applied to unveil these structures from the corresponding magnetic resonance imaging volume. Scalp and cortical surface are estimated from the scanned volume to improve depth perception. An alignment algorithm between the real and scanned heads is devised to visually feedback the position of the stylus of the digitizer. Off-screen rendering of the depthmaps of the visible surfaces makes spatial positioning of a 2D interaction pointer possible.
Results: We evaluated the alignment accuracy using four to eight anatomical landmarks and found seven to be a good compromise between precision and efficiency. Next, we evaluated reproducibility in positioning five arbitrarily chosen points on three volunteers by four operators over five sessions. In every session, seven anatomical landmarks were applied in the alignment of the real and the scanned head. For the same volunteer, one-way analysis of variance (ANOVA) revealed no significant differences within the five points digitized by the same operator over five sessions ( = 0.05). In addition, preliminary study of motor cortex activation by right-hand finger tapping showed the potential of our approach to increase functional fNIRS reproducibility.
Conclusions: Results of experiments suggest that the enhancement of the visualization of the location of the probes on the scalp, relative to the underlying cortical structures, improves reproducibility of fNIRS measurements. As further work, we plan to study the fNIRS reproducibility in other cortical regions and in clinical settings using the proposed system.

Integration of Spatial Information Increases Reproducibility in Functional Near-Infrared Spectroscopy [online]
Authors: Sergio Luiz Novi, Edwin Johan Forero, Jose Angel Ivan Rurianes Silva, Nicolas Gabriel S. R. de Souza, Giovani Grisotti Martins, Andres Quiroga, Shin-Ting Wu, and Rickson C. Mesquita
Published in Frontiers in Neuroscience
Abstract
As functional near-infrared spectroscopy (fNIRS) is developed as a neuroimaging technique and becomes an option to study a variety of populations and tasks, the reproducibility of the fNIRS signal is still subject of debate. By performing test-retest protocols over different functional tasks, several studies agree that the fNIRS signal is reproducible over group analysis, but the inter-subject and within-subject reproducibility is poor. The high variability at the first statistical level is often attributed to global systemic physiology. In the present work, we revisited the reproducibility of the fNIRS signal during a finger-tapping task across multiple sessions on the same and different days. We expanded on previous studies by hypothesizing that the lack of spatial information of the optodes contributes to the low reproducibility in fNIRS, and we incorporated a real-time neuronavigation protocol to provide accurate cortical localization of the optodes. Our proposed approach was validated in 10 healthy volunteers, and our results suggest that the addition of neuronavigation can increase the within-subject reproducibility of the fNIRS data, particularly in the region of interest. Unlike traditional approaches to positioning the optodes, in which low intra-subject reproducibility has been found, we were able to obtain consistent and robust activation of the contralateral primary motor cortex at the intra-subject level using a neuronavigation protocol. Overall, our findings support the hypothesis that at least part of the variability in fNIRS cannot be only attributed to global systemic physiology. The use of neuronavigation to guide probe positioning, as proposed in this work, has impacts to longitudinal protocols performed with fNIRS. The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required. The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required. The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required. The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required.

Interactive Patient-Customized Curvilinear Reformatting for Improving Neurological Planning [draft|supplemental video]
Authors: Shin-Ting Wu, Wallace Souza Loos, Dayvid Leonardo de Castro Oliveira, Fernando Cendes, Clarissa L. Yasuda, and Enrico Ghizoni
Published in International Journal of Computer Assisted Radiology and Surgery
Abstract
The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required. The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required. The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required. The curvilinear reformatting tool on the supratentorial compartment is applied to peel off the tissues to the depth of the dura-mater, revealing the cortical and vascular spatial relationships. The major advantage of our proposed tool over the known one is that co-registration of anatomical and vascular volumes is not required.

Toward Multimodal Diagnostic Exploratory Visualization of Focal Cortical Dysplasia [draft|supplemental video]
Authors: Shin-Ting Wu, Raphael Voltoline, Wallace Loos, José Angel Iván Rubianes Silva, Lionis Watanabe, Bárbara Amorim, Ana Carolina Coan, Fernando Cendes, and Clarissa L. Yasuda
Published in IEEE Computer Graphics and Applications (vol. 38, issue no. 03, 2018)
Presented in IEEE VIS 2018 - October 25 2018 - Berlin, Germany
Abstract
Focal cortical dysplasia (FCD) is a malformation of cortical development and a common cause of pharmacoresistant epilepsy. Resective surgery of clear-cut lesions may be curative. However, the localization of the seizure focus and the evaluation of its spatial extent can be challenging in many situations. For concordance assessment, medical studies show the relevance of accurate correlation of multisource imaging sequences. to improve the sensitivity and specificity of the evaluation. In this paper, we share the process we went through to reach our simple, but effective, solution for integrating multi-volume rendering into an exploratory visualization environment for the diagnosis of FCD. We focus on fetching of multiple data assigned to a sample when they are rendered. Knowing that the major diagnostic role of multiple volumes is to complement information, we demonstrate that appropriate geometric transformations in the texture space are sufficient for accomplishing this task. This allows us to fully implement our proposal in the OpenGL rendering pipeline and to easily integrate it into the existing visual diagnostic application. Both time performance and the visual quality of our proposal were evaluated with a set of clinical data volumes for assessing the potential practical impact of our solution in routine diagnostic use.

Cortical Envelope Modeling for Interactive Patient-Customized Curvilinear Reformatting in the Native Space [google books]
Authors: Wallace Souze Loos, Clarissa Lin Yasuda, Fernando Cendes and Wu, Shin-Ting
Published in Lecture Notes in Computer Science book series (LNCS, volume 10549)
Abstract
Focal cortical dysplasia is one of the most common cause of medically refractory epilepsy. Its imaging features include cortical architectural abnormalities and abnormal structural arrangement at the interface between the grey matter and the white matter. It is well-known that curvilinear multiplanar reformatting (CMPR), consisting in re-slicing the brain almost prependicular to the inward folding gyri from the view of anatomical planes, enhances the visualization of these abnormalities. In this paper, we present yet another interactive modeling of a patient-customized cortical envelope with which we can automatically re-slice the brain volume in a fashion similar to CMPR. Although our proposal requires fewer user interactions in comparison with the previous proposals, we show that the outcomes of re-slicing match those of the conceived CMPR.

A View-independent Line-Coding Colormap for Diffusion Tensor Imaging [submitted version in pdf]
Authors: Wu, Shin - Ting, Raphael Voltoline Ramos and Clarissa Lin Yasuda
Published in Special Section on SIBGRAPI 2016 of Computers & Graphics
Abstract
Diffusion Tensor Imaging is a noninvasive technique promising for assessing the integrity of white matter tracts in the brain through the measurement of the movement of water. Because of the dimensions of the data involved, visualization of slice-by-slice images is still a challenge, and the colormaps for conveying the spatial direction of the major eigenvector of the diffusivity tensors widely adopted are ambiguous. The present paper addresses the issue of how to ameliorate this ambiguity. We propose a new line-coding color scheme, contemplating human visual perception in conjunction with the classic Hue-Saturation-Value color model. Experiments with neuroimages were also conducted to assess the potential of the proposal in the perception of spatial orientations in 2D views.

Interactive Visuaization of the Cranio-Cerebral Correspondences for 10/20, 10/10 and 10/5 Systems [pdf]
Authors: José Angel Iván Rubianes Silva, Fabio Enrique Suarez Burgos and Wu, Shin - Ting
Published in Proceedings of XXIX SIBGRAPI - Conference on Graphics, Patterns and Images
Abstract
Electroencephalogram (EEG) is a method that records electrical activities of the brain. Reliable interpretation of its measurements rely on accurate correspondence of the scalp electrodes and the underlying cortical surface. To standardize comparative studies international 10/20, 10/10 and 10/5 systems for the placement of electrodes have been proposed to specify the locations of scalp EEG sensors under the assumption that there is a consistent correlation between these sites and the structure of the cerebral cortex. However, several studies have demonstrated that the cranio-cerebral correlations vary greatly. For enhancing the electrophysiological analyses, an algorithm is presented in this paper, allowing the multimodal visualization of EEG and magnetic resonance scan in the patient's native space. The key to our solution is twofold: an interactive image-based electrode placement algorithm and an extended GPU-based multimodal raycasting algorithm. Experimental results show that with the present tool one can easily assess the cranio-cerebral correspondences even when the brain tissue is displaced by structural lesions.

Pre-Alignment for Co-registration in Native Space [pdf]
Authors: Wu, Shin - Ting, Augusto C. Valente, Lionis S. Watanabe, Clarissa L. Yasuda, Ana Carolina Coan and Fernando Cendes
Published in Proceedings of XXVII SIBGRAPI - Conference on Graphics, Patterns and Images (Sibgrapi 2014 Samsung Best Paper Award in Computer Vision)
Abstract
For nonlesional patients, the correct localization of the epileptogenic foci in native space remains a great challenge. Non-invasive functional PET images that provide information about cerebral activities may reveal the origin of seizure activity, but without precise anatomical detail. Co-registration of the functional images with MR images on the basis of maximization of mutual information (MMI) has shown to be very promising in improving presurgical evaluation. Nevertheless, a mutual information (MI) function is non-convex and the convergence of an algorithm to its optimum is guaranteed only if the initial estimate lies in its convex vicinity. We present in this paper a generally applicable method that pre-aligns the DICOM images such that their relative position becomes close to an optimum. The key to our solution is a robust user-guided interactive procedure to extract valid voxels, for both the centroid estimation and the registration. Aiming at comparative analysis, we introduce a numerical condition to quantify registration errors. The results are acceptable when we consider the intrinsic problems of the MMI-based registration algorithm we implemented.

Estudo da Aceitabilidade de Usuários sobre o Uso de Wiimote como Interface de um Cursor 3D [pdf]
Authors: Roberto Scalco and Wu, Shin - Ting
Published in Proceedings of INTERTECH' 2014 - XIII International Conference on Engineering and Technology Education, Guimarães, Portugal
Abstract
Aiming at the application of Wiimote as a 3D cursor controller for accurate spatial placements, this article presents an analysis of test results of motion tracking objects and a survey with users who used the control Wiimote of the Nintendo Wii to move a 3D cursor. The time to perform the tasks and the difference between the object position and the position of the target were used to determine the characteristics of a learning curve of the pointing and motion tracking objects with the Wiimote. The survey results allow to confirm, from the previous experience of the users, such as familiarity with the use of Wiimote, experience with 3D modeling softwares or familiarity with 3D games, the points that should be improved in the proposal of this framework.

Query Tools for Interactive Exploration of 3D Neuroimages: Cropping, Probe and Lens [pdf]
Authors: Wu, Shin - Ting, José Elías Yuri Vidalón, Wallace Souza Loos and Ana Carolina Coan
Published in Proceedings of XXVI SIBGRAPI - Conference on Graphics, Patterns and Images
Abstract
Dynamic queries continuously update the data that is visualized in accordance with the user actions. They are typically applied for visual information seeking. This paper proposes to introduce this interaction style for exploring 3D medical neuroimages in its original form, enhancing visual seeking technology in a medical diagnostic procedure. More precisely, we present three dynamic query tools that allow the user to change the focus on-the-fly, while the surrounding tissue is preserved. They are a curvilinear cropper, a volumetric probe and a movable magnifying lens. Once information-preserving visualization is essential for accurate diagnosis and legal protection, the dataset is in its original form. The originality of our work relies on the input interface through which an expert can directly manipulate those tools on the raw data and the responsiveness of each displayed voxel by exploiting the power of GPUs. The proposed techniques have been integrated in a visualization prototype and were assessed by the neuroimaging experts, who were be able to identify subtle lesions in the brain.

Snapping a Cursor on Volume Data [pdf]
Authors: Wu, Shin - Ting, José Elías Yuri Vidalón and Lionis de Souza Watanabe
Published in Proceedings of 24th Brazilian Symposium on Computer Graphics and Image Processing
Abstract
In this paper we explore the architecture of GPU-based volume ray-casting to control the cursor movements on surfaces of volume data only on the basis of their sampled scalar values. This method does not rely on building a tight proxy geometry nor computing local iso-surface parametrization. In this setting only a few instructions should be included in a ray-casting shader: at every fragment the depth of the closest non-transparent voxel along each viewing ray is calculated and stored in the depth buffer. Its application in the manipulation of 3D medical images has, however, a broad spectrum. Two of them are presented. The proposed technique is very simple and fast, yet produces very nice and intuitive visual feedbacks.

Interactive Curvilinear Reformatting in Native Space [article]
Authors: Wu, Shin - Ting, Clarissa Lin Yasuda and Fernando Cendes
Published in IEEE Transactions on Visualization and Computer Graphics
Abstract
Curvilinear reformatting of 3D magnetic resonance imaging data has been recognized by the medical community as a helpful non-invasive tool for displaying the cerebral anatomy. It consists of automatically creating, with respect to a reference surface, a series of equidistant curvilinear slices at progressively deeper cuts. In comparison with planar slices, it allows more precise localization of lesions and identification of subtle structural abnormalities. However, current curvilinear reformatting tools either rely on the time-consuming manual delineation of guiding curves on 2D slices, or require costly automatic brain segmentation procedures. In addition, they extract the skin and skull, impeding a precise topographic correlation between the location of the brain lesion and skin surface. This impairs planning of craniotomy for neurosurgery, and of the appropriate implantation of electrodes for intracranial electroencephalography in presurgical evaluation. In this work, we present a novel approach based on direct manipulation of the visualized volume data. By using a 3D painting metaphor, the reference surface can be defined incrementally, according to the principle that the user interacts with what s/he sees. As a response, an animation of the reformatting process is displayed. The focus of this paper is a new volume tagging algorithm behind user interactions. It works at an interactive frame rate on current graphics hardware.

A framework for GPU-based application-independent 3D interactions [article]
Authors: Harlen Costa Batagelo and Wu, Shin - Ting
Published in The Visual Computer: International Journal of Computer Graphics
Abstract
Direct manipulation using pointing devices commonly relies on basic interaction tasks such as selection and precise cursor positioning. Traditionally, such tasks use geometric attributes computed on the basis of application-dependent intersection algorithms on the CPU. However, with the recent ability of using GPUs to perform geometry modeling tasks and even to create new primitives on-the-fly, geometric attributes computed on the CPU are often invalid. We analyze a new paradigm for correctly computing such attributes based on providing, for each pixel of the rendered models, application-defined data and elements of discrete differential geometry computed solely on the GPU. We validate this by showing how many direct manipulation tasks presented in the literature require only these data, and present an interaction framework that exploits such paradigm. Implementation results are presented.

Application-independent direct manipulation using geometry attributes computed on the GPU [pdf]
Authors: Harlen Costa Batagelo and Wu, Shin - Ting
Published in Proceedings of 20th Brazilian Symposium on Computer Graphics and Image Processing
Abstract
Direct manipulation with 3D meshes often require the computation of distinct sets of geometry attributes on the basis of local regions of the model in system memory. In this work, we present a simple yet general GPU-based framework for computing these attributes without depending on application-specific algorithms. In particular, it provides, for each pixel of the rendered model, elements of discrete differential geometry that require only the vertex data and 1-ring connectivity of each vertex stored in video memory. We validate our framework by showing how it can subsume the computation of attributes used by many direct manipulation tasks presented on the literature, and show how it can work with geometry modified on the vertex or geometry processor. Implementation results are presented.

Estimating Curvatures and their Derivatives on Meshes of Arbitrary Topology from Sampling Directions [pdf]
Authors: Harlen Costa Batagelo and Wu, Shin - Ting
Published in The Visual Computer: International Journal of Computer Graphics
Abstract
Estimation of local differential geometry properties becomes an important processing step in a variety of applications, ranging from shape analysis and recognition to photorealistic image rendering. This paper presents yet another approach to compute those properties, with comparable numerical and accuracy performances to previous works. The key difference in our approach is simplicity, allowing for direct implementation on the GPU. Experimental results are provided to support our statement.

What You See Is What You Snap: Snapping to Geometry Deformed on the GPU [pdf]
Authors: Harlen Costa Batagelo and Wu, Shin - Ting
Published in Proceedings of ACM SIGGRAPH 2005 Symposium on Interactive 3D Graphics and Game
Abstract
We present a simple yet effective snapping technique for constraining the motion of the cursor of an input device to the surface of 3D models whose geometry is arbitrarily deformed by a programmable hardware fragment and vertex processor. The technique works in image space and thus snaps the cursor to the geometry actually rendered instead of the geometry originally submitted to the rendering pipeline. We also present a method to establish a correspondence between snapped geometry in image space and object space, and an efficiency improvement based on the control of (modeless) feedback frequency for the user actions. Performance tests are conducted and compared against the standard picking and snapping algorithm used by the D3DX library of the Microsoft Direct3D API. We conclude by emphasizing the feasibility of our algorithm when facing the new advances of the graphics hardware for deforming geometry on the GPU.

Picking and Snapping for 3D Input Devices [compressed PostScript| pdf| compressed ppt|supplemental video 1|supplemental video 2]
Authors: Wu, Shin - Ting, Marcel Abrantes, Daniel Tost and Harlen Costa Batagelo
Published in Proceedings of Sibgrapi 2003
Abstract
A picking mechanism (pointing and indicating) with the cursor is essential for any direct-manipulation application. The windowing systems, under which control a direct-manipulation application runs, provide facilities that together with special utility routines allow identifying which object within the region the user is pointing at. Such picking algorithms have been widely used for selecting objects under a 2D mouse cursor. In this paper, we present a simple yet effective application-independent 3D picking algorithm for 3D input devices. We also discuss a differential geometry based surface constraint that can be applied to the 3D cursor position for improving points matching. In order to demonstrate the techniques, two sample applications using a 3D input device are shown.

Dynamic Scene Occlusion Culling using a Regular Grid [compressed PostScript| pdf]
Authors: Harlen Costa Batagelo and Wu, Shin - Ting
Published in Proceedings of Sibgrapi 2002
Abstract
We present an output-sensitive occlusion culling algorithm for densely occluded dynamic scenes where both the viewpoint and objects move arbitrarily. Our method works on a regular grid that represents a volumetric discretization of the space and uses the opaque regions of the scene as virtual occluders. We introduce new techniques of efficient traversal of voxels, object discretization and occlusion computation that strengthen the benefits of regular grids in dynamic scenes. The method also exploits temporal coherence and realizes occluder fusion in object-space. For each frame, the algorithm computes a conservative set of visible objects that greatly accelerates the visualization of complex dynamic scenes. We discuss the results of a 2D and 3D case implementation.

Interactive 3D Geometric Modelers with 2D UI [compressed PostScript| pdf]
Authors: Wu, Shin - Ting and Marcelo de Gomensoro Malheiros
Published in WSCG'2002 Conference Proceedings
Abstract
This paper presents an object-oriented framework which enhances the collaboration of three categories of experts that play fundamental role in the development of a software for interactive 3D geometric modelers. It aims at three purposes. First, it supports application developers to build a graphics interface for manipulating with 2D devices their own 3D data representations, without intimate knowledge of its internal structure. Second, it provides facilities for interface researchers to create and experiment 3D widgets from reusable draggers and 2D-3D mapping strategies. Finally, it permits graphics experts to implement sophisticated draggers and complex 2D-3D mapping strategies by overriding operations of the predefined abstract classes.

CoLab: a Co-Constructive Learning Environment (CoLab: um Ambiente de Aprendizagem Co-Construtiva) [compressed PostScript| pdf] (in Portuguese)
Authors: Paulo Henrique Fisch de Brito and Wu, Shin - Ting
Published in eletronic media by SBC 2001-WIE 2001: VII Workshop de Informática na Escola (31/07-2/08, Fortaleza-CE)
Abstract
To our knowledge, most of collaborative learning systems use generic collaboration tools, such as chat and email. They may be applied in a variety of knowledge areas, but they underuse the computers graphics power in acting as support to co-construction of knowledge in some specific areas, where the visual language is often employed for conveying an idea. This paper proposes an architecture for environments that permit co-constructive learning. A prototype of this architecture applied on the teaching of some topics in Mathematics, called CoLab, is presented.

Towards Consistency in a Heterogeneous Collaborative Geometric Modeling Environment [compressed PostScript| pdf]
Authors: Luiz Gonzaga da Silveira Jr and Wu, Shin-Ting
Published in Proceedings of Sibgrapi 2002
Abstract
This paper presents a hybrid system architecture for collaborative geometric modeling applications, as a tradeoff solution between replicated and centralized approaches. It addresses the geometric inconsistency that may be presented by a replicated-based architecture and the tight visualization coupling in the centralized one. The proposed approach provides a infrastructure to ensure the same geometric processing for a highly heterogeneous computing environment. Moreover, it allows a decoupled visualization and interaction on each user's workspace. A prototype has been implemented and evaluated concerning with geometric consistency and responsiveness.

An Object-Oriented Groupware Framework for Developing Collaborative 3D-Modelers [compressed PostScript| pdf]
Authors: Luiz Gonzaga da Silveira Jr and Wu, Shin-Ting
Published in Proceedings of Third Eurographics Workshop on Parallel Graphics and Visualization
Abstract
We present an object-oriented framework to support the development of collaborative (real-time shared) 3D modeling systems. For data integrity reasons, our research aims at enabling geographically dispersed end-users to create, to inspect, and to modify interactive and synchronously the shareable 3D geometric data in different (heterogeneous) computing environments.

MTK: A Direct 3D Manipulation Toolkit [compressed PostScript]
Authors: Marcelo de Gomensoro Malheiros, Flávio Fernandes Navarro and Wu, Shin - Ting
Published in SCCG98 Conference Proceedings
Abstract
Advances in computer technology have made interactive 3D graphics systems a common tool for a variety of areas. Notwithstanding, most of such systems relies on popular 2D devices. To relieve system developers from the burden of implementing mapping techniques between 2D devices and 3D application data, some generic libraries have been proposed. However, those libraries still present limitations, either being complex to program or being limited in its interactive flexibility. As an alternative, we present a general purpose toolkit called MTK, which provides only basic interaction tasks. We also show that these tasks may be used to build sophisticated direct 3D manipulation techniques.

Fuzzy sets on drawing fair plane curves [compressed PostScript]
Authors: Marcelo Cordeiro Bernardes and Wu, Shin-Ting
Published in Sibgrapi 1995 Proceedings
Abstract
In this paper an approach for interpolating a given sequence of points by a fair plane curve is presented. Since the fairness concept is subjective, a non-classical modeling tool - fuzzy sets - is used. The fuzzyfication and defuzzyfication techniques are explained. We show that the user can be integrated into the defuzzyfication technique in order to obtain "the most fair" curve. Some results of our implementation are included.

An approach to drawing fair planar open curves [compressed PostScript]
Authors: Marcelo Cordeiro Bernardes, Wu, Shin-Ting and Ítala M. L. D'Ottaviano
Published in WSCG1995 International Conferences in Central Europe on Computer Graphics, Visualization and Computer Vision Proceedings
Abstract
In this paper an approach for interpolating a given sequence of points by a fair planar curve is presented. Since the fairness concept is subjective, a non-classical modeling tool - fuzzy sets - is used and interactive facilities are provided. Some results of our implementation are included.