DevLan/vispubs huggingface dataset:
Level set segmentation from multiple non-uniform volume datasets
Authors: Ken Museth, David E. Breen, Leonid Zhukov, Ross T. Whitaker
Published at Vis, 2002

Typically 3-D MR and CT scans have a relatively high resolution in the scanning X-Y plane, but much lower resolution in the axial Z direction. This non-uniform sampling of an object can miss small or thin structures. One way to address this problem is to scan the same object from multiple directions. In this paper we describe a method for deforming a level set model using velocity information derived from multiple volume datasets with non-uniform resolution in order to produce a single high-resolution 3D model. The method locally approximates the values of the multiple datasets by fitting a distance-weighted polynomial using moving least-squares. The proposed method has several advantageous properties: its computational cost is proportional to the object surface area, it is stable with respect to noise, imperfect registrations and abrupt changes in the data, it provides gain-correction, and it employs a distance-based weighting to ensures that the contributions from each scan are properly merged into the final result. We have demonstrated the effectiveness of our approach on four multi-scan datasets, a Griffin laser scan reconstruction, a CT scan of a teapot and MR scans of a mouse embryo and a zucchini.
Maximum entropy light source placement
Authors: Stefan Gumhold
Published at Vis, 2002

Finding the "best" viewing parameters for a scene is a difficult but very important problem. Fully automatic procedures seem to be impossible as the notion of "best" strongly depends on human judgment as well as on the application. In this paper a solution to the sub-problem of placing light sources for given camera parameters is proposed. A light position is defined to be optimal, when the resulting illumination reveals more about the scene than illuminations from all other light positions, i.e. the light position maximizes information that is added to the image through the illumination. With the help of an experiment with several subjects we could adapt the information measure to the actually perceived information content. We present fast global optimization procedures and solutions for two and more light sources.
NASA's great zooms: a case study
Authors: Gregory W. Shirah, Horace Mitchell
Published at Vis, 2002

This paper examines a series of NASA outreach visualizations created using several layers of remote sensing satellite data ranging from 4-kilometers per pixel to I-meter per pixel. The viewer is taken on a seamless, cloud free journey from a global view of the Earth down to ground level where buildings, streets, and cars are visible. The visualizations were produced using a procedural shader that takes advantage of accurate georegistration and color matching between images. The shader accurately and efficiently maps the data sets to geometry allowing for animations with few perceptual transitions among data sets. We developed a pipeline to facilitate the production of over twenty zoom visualizations. Millions of people have seen these visualizations through national and international media coverage.
Non-photorealistic volume rendering using stippling techniques
Authors: Aidong Lu, Christopher J. Morris 0001, David S. Ebert, Penny Rheingans, Charles D. Hansen
Published at Vis, 2002

Simulating hand-drawn illustration techniques can succinctly express information in a manner that is communicative and informative. We present a framework for an interactive direct volume illustration system that simulates traditional stipple drawing. By combining the principles of artistic and scientific illustration, we explore several feature enhancement techniques to create effective, interactive visualizations of scientific and medical datasets. We also introduce a rendering mechanism that generates appropriate point lists at all resolutions during an automatic preprocess, and modifies rendering styles through different combinations of these feature enhancements. The new system is an effective way to interactively preview large, complex volume datasets in a concise, meaningful, and illustrative manner. Volume stippling is effective for many applications and provides a quick and efficient method to investigate volume models.
Optimized view-dependent rendering for large polygonal datasets
Authors: Jihad El-Sana, Eitan Bachmant
Published at Vis, 2002

In this paper we are presenting a novel approach for rendering large datasets in a view-dependent manner. In a typical view-dependent rendering framework, an appropriate level of detail is selected and sent to the graphics hardware for rendering at each frame. In our approach, we have successfully managed to speed up the selection of the level of detail as well as the rendering of the selected levels. We have accelerated the selection of the appropriate level of detail by not scanning active nodes that do not contribute to the incremental update of the selected level of detail. Our idea is based on imposing a spatial subdivision over the view-dependence trees data-structure, which allows spatial tree cells to refine and merge in real-time rendering to comply with the changes in the active nodes list. The rendering of the selected level of detail is accelerated by using vertex arrays. To overcome the dynamic changes in the selected levels of detail we use multiple small vertex arrays whose sizes depend on the memory on the graphics hardware. These multiple vertex arrays are attached to the active cells of the spatial tree and represent the active nodes of these cells. These vertex arrays, which are sent to the graphics hardware at each frame, merge and split with respect to the changes in the cells of the spatial tree.
Oriented tensor reconstruction: tracing neural pathways from diffusion tensor MRI
Authors: Leonid Zhukov, Alan H. Barr
Published at Vis, 2002

In this paper we develop a new technique for tracing anatomical fibers from 3D tensor fields. The technique extracts salient tensor features using a local regularization technique that allows the algorithm to cross noisy regions and bridge gaps in the data. We applied the method to human brain DT-MRI data and recovered identifiable anatomical structures that correspond to the white matter brain-fiber pathways. The images in this paper are derived from a dataset having 121/spl times/88/spl times/60 resolution. We were able to recover fibers with less than the voxel size resolution by applying the regularization technique, i.e., using a priori assumptions about fiber smoothness. The regularization procedure is done through a moving least squares filter directly incorporated in the tracing algorithm.
Out-of-core rendering of massive geometric environments
Authors: Gokul Varadhan, Dinesh Manocha
Published at Vis, 2002

We present an external memory algorithm for fast display of very large and complex geometric environments. We represent the model using a scene graph and employ different culling techniques for rendering acceleration. Our algorithm uses a parallel approach to render the scene as well as fetch objects from the disk in a synchronous manner. We present a novel prioritized prefetching technique that takes into account LOD-switching and visibility-based events between successive frames. We have applied our algorithm to large gigabyte-sized environments that are composed of thousands of objects and tens of millions of polygons. The memory overhead of our algorithm is output sensitive and is typically tens of megabytes. In practice, our approach scales with the model sizes, and its rendering performance is comparable to that of an in-core algorithm.
PMR: point to mesh rendering, a feature-based approach
Authors: Tamal K. Dey, James Hudson
Published at Vis, 2002

Within the field of computer graphics and visualization, it is often necessary to visualize polygonal models with large number of polygons. Display quality is mandatory, but it is also desirable to have the ability to rapidly update the display in order to facilitate interactive use. Point based rendering methods have been shown effective for this task. Building on this paradigm we introduce the PMR system which uses a hierarchy both in points and triangles for rendering. This hierarchy is fundamentally different from the ones used in existing methods. It is based on the feature geometry in the object space rather than its projection in the screen space. This provides certain advantages over the existing methods.
PRIMA: A case study of using information visualization techniques for patient record analysis
Authors: Donna L. Gresh, David A. Rabenhorst, Amnon Shabo, Shimon Slavin
Published at Vis, 2002

We have created an application, called PRIMA (Patient Record intelligent Monitoring and Analysis), which can be used to visualize and understand patient record data. It was developed to better understand a large collection of patient records of bone marrow transplants at Hadassah Hospital in Jerusalem, Israel. It is based on an information visualization toolkit, Opal, which has been developed at the IBM T.J. Watson Research Center. Opal allows intelligent, interactive visualization of a wide variety of different types of data. The PRIMA application is generally applicable to a wide range of patient record data, as the underlying toolkit is flexible with regard to the form of the input data. This application is a good example of the usefulness of information visualization techniques in the bioinformatics domain, as these techniques have been developed specifically to deal with diverse sets of often unfamiliar data. We illustrate several unanticipated findings which resulted from the use of a flexible and interactive information visualization environment.
Probabilistic surfaces: point based primitives to show surface uncertainty
Authors: Gevorg Grigoryan, Penny Rheingans
Published at Vis, 2002

Efficient and informative visualization of surfaces with uncertainties is an important topic with many applications in science and engineering. Examples include environmental pollution borderline identification, identification of the limits of an oil basin, or discrimination between contaminated and healthy tissue in medicine. This paper presents an approach for such visualization using points as display primitives. The approach is to render each polygon as a collection of points and to displace each point from the surface in the direction of the surface normal by an amount proportional to some random number multiplied by the uncertainty level at that point. This approach can be used in combination with other techniques such as pseudo-coloring and shading to give rise to efficient and revealing visualizations. The method is used to visualize real and simulated tumor formations with uncertainty of tumor boundaries.
QuadTIN: quadtree based triangulated irregular networks
Authors: Renato Pajarola, Marc Antonijuan, Roberto Lario
Published at Vis, 2002

Interactive visualization of large digital elevation models is of continuing interest in scientific visualization, GIS, and virtual reality applications. Taking advantage of the regular structure of grid digital elevation models, efficient hierarchical multiresolution triangulation and adaptive level-of-detail (LOD) rendering algorithms have been developed for interactive terrain visualization. Despite the higher triangle count, these approaches generally outperform mesh simplification methods that produce irregular triangulated network (TIN) based LOD representations. In this project we combine the advantage of a TIN based mesh simplification preprocess with high-performance quadtree based LOD triangulation and rendering at run-time. This approach, called QuadTIN, generates an efficient quadtree triangulation hierarchy over any irregular point set that may originate from irregular terrain sampling or from reducing oversampling in high-resolution grid digital elevation models.
Rendering the first star in the Universe - A case study
Authors: Ralf Kähler, Donna J. Cox, Robert Patterson, Stuart Levy, Hans-Christian Hege, Tom Abel
Published at Vis, 2002

For quantitative examination of phenomena that simultaneously occur on very different spatial and temporal scales, adaptive hierarchical schemes are required. A special numerical multilevel technique, associated with a particular hierarchical data structure, is so-called adaptive mesh refinement (AMR). It allows one to bridge a wide range of spatial and temporal resolutions and therefore gains increasing popularity. We describe the interplay of several visualization and VR software packages for rendering time dependent AMR simulations of the evolution of the first star in the universe. The work was done in the framework of a television production for Discovery Channel television, "The Unfolding Universe.". Parts of the data were taken from one of the most complex AMR simulation ever carried out: It contained up to 27 levels of resolution, requiring modifications to the texture based AMR volume rendering algorithm that was used to depict the density distribution of the gaseous interstellar matter. A voice and gesture controlled CAVE application was utilized to define camera paths following the interesting features deep inside the computational domains. Background images created from cosmological computational data were combined with the final renderings.
Scalable alignment of large-format multi-projector displays using camera homography trees
Authors: Han Chen, Rahul Sukthankar, Grant Wallace, Kai Li 0001
Published at Vis, 2002

This paper presents a vision-based geometric alignment system for aligning the projectors in an arbitrarily large display wall. Existing algorithms typically rely on a single camera view and degrade in accuracy as the display resolution exceeds the camera resolution by several orders of magnitude. Naive approaches to integrating multiple zoomed camera views fail since small errors in aligning adjacent views propagate quickly over the display surface to create glaring discontinuities. Our algorithm builds and refines a camera homography tree to automatically register any number of uncalibrated camera images; the resulting system is both faster and significantly more accurate than competing approaches, reliably achieving alignment errors of 0.55 pixels on a 24-projector display in under 9 minutes. Detailed experiments compare our system to two recent display wall alignment algorithms, both on our 18 Megapixel display wall and in simulation. These results indicate that our approach achieves sub-pixel accuracy even on displays with hundreds of projectors.
Sea of images
Authors: Daniel G. Aliaga, Thomas A. Funkhouser, Dimah Yanovsky, Ingrid Carlbom
Published at Vis, 2002

A long-standing research problem in computer graphics is to reproduce the visual experience of walking through a large photorealistic environment interactively. On one hand, traditional geometry-based rendering systems fall short of simulating the visual realism of a complex environment. On the other hand, image-based rendering systems have to date been unable to capture and store a sampled representation of a large environment with complex lighting and visibility effects. In this paper, we present a "sea of images," a practical approach to dense sampling, storage, and reconstruction of the plenoptic function in large, complex indoor environments. We use a motorized cart to capture omnidirectional images every few inches on a eye-height plane throughout an environment. The captured images are compressed and stored in a multiresolution hierarchy suitable for real-time prefetching during an interactive walkthrough. Later, novel images are reconstructed for a simulated observer by resampling nearby captured images. Our system acquires 15,254 images over 1,050 square feet at an average image spacing of 1.5 inches. The average capture and processing time is 7 hours. We demonstrate realistic walkthroughs of real-world environments reproducing specular reflections and occlusion effects while rendering 15-25 frames per second.
Seamster: inconspicuous low-distortion texture seam layout
Authors: Alla Sheffer, John C. Hart
Published at Vis, 2002

Surface texturing aids the visualization of polygonal meshes by providing additional surface orientation cues and feature annotations. Such texturing is usually implemented via texture mapping, which is easier and more effective when the distortion of the mapping from the surface to the texture map is kept small. We have previously shown that distortion occurs when areas of high surface curvature are flattened into the texture map. By cutting the surface in these areas one can reduce texture map distortion at the expense of additional seam artifacts. This paper describes a faster technique for guiding a texture map seam through high distortion regions, while restricting the seam to regions of low visibility. This results in distortion reducing seams that are less visually distracting and take less time to compute. We have also observed that visibility considerations improve the speed of a recent method that adds cuts to reduce a surface genus.
Semotus Visum: a flexible remote visualization framework
Authors: Eric Luke, Charles D. Hansen
Published at Vis, 2002

By offering more detail and precision, large data sets can provide greater insights to researchers than small data sets. However, these data sets require greater computing resources to view and manage. Remote visualization techniques allow the use of computers that cannot be operated locally. The Semotus Visum framework applies a high-performance client-server paradigm to the problem. The framework utilizes both client and server resources via multiple rendering methods. Experimental results show the framework delivers high frame rates and low latency across a wide range of data sets.
Simulating fire with texture splats
Authors: Xiaoming Wei, Wei Li 0004, Klaus Mueller 0001, Arie E. Kaufman
Published at Vis, 2002

We propose the use of textured splats as the basic display primitives for an open surface fire model. The high-detail textures help to achieve a smooth boundary of the fire and gain the small-scale turbulence appearance. We utilize the Lattice Boltzmann Model (LBM) to simulate physically-based equations describing the fire evolution and its interaction with the environment (e.g., obstacles, wind and temperature). The property of fuel and non-burning objects are defined on the lattice of the computation domain. A temperature field is also incorporated to model the generation of smoke from the fire due to incomplete combustion. The linear and local characteristics of the LBM enable us to accelerate the computation with graphics hardware to reach real-time simulation speed, while the texture splat primitives enable interactive rendering frame rates.
Tensor field visualisation using adaptive filtering of noise fields combined with glyph rendering
Authors: Andreas Sigfridsson, Tino Ebbers, Einar Heiberg, Lars Wigström
Published at Vis, 2002

While many methods exist for visualising scalar and vector data, visualisation of tensor data is still troublesome. We present a method for visualising second order tensors in three dimensions using a hybrid between direct volume rendering and glyph rendering. An overview scalar field is created by using three-dimensional adaptive filtering of a scalar field containing noise. The filtering process is controlled by the tensor field to be visualised, creating patterns that characterise the tensor field. By combining direct volume rendering of the scalar field with standard glyph rendering methods for detailed tensor visualisation, a hybrid solution is created. A combined volume and glyph renderer was implemented and tested with both synthetic tensors and strain-rate tensors from the human heart muscle, calculated from phase contrast magnetic resonance image data. A comprehensible result could be obtained, giving both an overview of the tensor field as well as detailed information on individual tensors.
TetFusion: an algorithm for rapid tetrahedral mesh simplification
Authors: Prashant Chopra, Jörg Meyer 0003
Published at Vis, 2002

This paper introduces an algorithm for rapid progressive simplification of tetrahedral meshes: TetFusion. We describe how a simple geometry decimation operation steers a rapid and controlled progressive simplification of tetrahedral meshes, while also taking care of complex mesh-inconsistency problems. The algorithm features a high decimation ratio per step, and inherently discourages any cases of self-intersection of boundary, element-boundary intersection at concave boundary-regions, and negative volume tetrahedra (flipping). We achieved rigorous reduction ratios of up to 98% for meshes consisting of 827,904 elements in less than 2 minutes, progressing through a series of level-of-details (LoDs) of the mesh in a controlled manner. We describe how the approach supports a balanced re-distribution of space between tetrahedral elements, and explain some useful control parameters that make it faster and more intuitive than 'edge collapse'-based decimation methods for volumetric meshes. Finally, we discuss how this approach can be employed for rapid LoD prototyping of large time-varying datasets as an aid to interactive visualization.
Visibility-guided simplification
Authors: Eugene Zhang, Greg Turk
Published at Vis, 2002

For some graphics applications, object interiors and hard-to-see regions contribute little to the final images and need not be processed. In this paper, we define a view-independent visibility measure on mesh surfaces based on the visibility function between the surfaces and a surrounding sphere of cameras. We demonstrate the usefulness of this measure with a visibility-guided simplification algorithm. Mesh simplification reduces the polygon counts of 3D models and speeds up the rendering process. Many mesh simplification algorithms are based on sequences of edge collapses that minimize geometric and attribute errors. By combining the surface visibility measure with a geometric error measure, we obtain simplified models with improvement proportional to the number of low visibility regions in the original models.
Visualizing dynamic molecular conformations
Authors: Johannes Schmidt-Ehrenberg, Daniel Baum, Hans-Christian Hege
Published at Vis, 2002

The bioactivity of a molecule strongly depends on its metastable conformational shapes and the transitions between these. Therefore, conformation analysis and visualization is a basic prerequisite for the understanding of biochemical processes. We present techniques for visual analysis of metastable molecular conformations. Core of these are flexibly applicable methods for alignment of molecular geometries, as well as methods for depicting shape and 'fuzziness' of metastable conformations. All analysis tools are provided in an integrated working environment. The described techniques are demonstrated with pharmaceutically active biomolecules.
Volume clipping via per-fragment operations in texture-based volume visualization
Authors: Daniel Weiskopf, Klaus Engel, Thomas Ertl
Published at Vis, 2002

We propose new clipping methods that are capable of using complex geometries for volume clipping. The clipping tests exploit per-fragment operations on the graphics hardware to achieve high frame rates. In combination with texture-based volume rendering, these techniques enable the user to interactively select and explore regions of the data set. We present depth-based clipping techniques that analyze the depth structure of the boundary representation of the clip geometry to decide which parts of the volume have to be clipped. In another approach, a voxelized clip object is used to identify the clipped regions.