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View-Dependent Visibility Optimization for Monte Carlo Volume visualization

COMPUTER GRAPHICS FORUM 2025年

作者： Lerzer, Nathan Dachsbacher, Carsten Karlsruhe Inst Technol Inst Visualizat & Data Anal Karlsruhe Germany

Compared to classic ray marching-based approaches, Monte Carlo ray tracing for volume visualization can provide faster frame times through progressive rendering, improved image quality, and allows for advanced illumination models more easily. Techniques such as the view-dependent optimization of visibility and illumination of important regions, however, have been formulated for ray marching and rely on stepwise sampling along rays, and are thus incompatible with free-flight distance sampling of state-of-the-art Monte Carlo methods. In this paper we derive such a view-dependent optimization for Monte Carlo ray tracing where the visibility to the camera, the illumination and opacity of important regions is optimized for both single and multiple scattering rendering. For this we define a post-interpolative importance function, introduce an efficient data structure to sample, approximate and optimize the integrated extinction along rays, and devise an efficient Monte Carlo estimator for interactive visualization. Our method enables view-dependent visibility optimization with moderate memory overhead and unbiased, progressive Monte Carlo volume visualization. We demonstrate our method for various volume data sets as well as for data-dependent and spatially-dependent importance functions.

关键词： CCS Concepts • human-centered computing → scientific visualization

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VortexTransformer: End-to-End Objective Vortex Detection in 2D Unsteady Flow Using Transformers

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COMPUTER GRAPHICS FORUM 2025年

作者： Zhang, X. Rautek, P. Hadwiger, M. King Abdullah Univ Sci & Technol Thuwal Saudi Arabia

Vortex structures play a pivotal role in understanding complex fluid dynamics, yet defining them rigorously remains challenging. One hard criterion is that a vortex detector must be objective, i.e., it needs to be indifferent to reference frame transformations. We propose VortexTransformer, a novel deep learning approach using point transformer architectures to directly extract vortex structures from pathlines. Unlike traditional methods that rely on grid-based velocity fields in the Eulerian frame, our approach operates entirely on a Lagrangian representation of the flow field (i.e., pathlines), enabling objective identification of both strong and weak vortex structures. To train VortexTransformer, we generate a large synthetic dataset using parametric flow models to simulate diverse vortex configurations, ensuring a robust ground truth. We compare our method against CNN and U-Net architectures, applying the trained models to real-world flow datasets. VortexTransformer is an end-to-end detector, which means that reference frame transformations as well as vortex detection are handled implicitly by the network, demonstrating the ability to extract vortex boundaries without the need for parameters such as arbitrary thresholds, or an explicit definition of a vortex. Our method offers a new approach to determining objective vortex labels by using the objective pairwise distances of material points for vortex detection and is adaptable to various flow conditions.

关键词： CCS Concepts Vector / tensor field visualization • computing methodologies → Neural networks • human-centered computing → scientific visualization

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A Flip-book of Knot Diagrams for Visualizing Surfaces in 4-Space

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COMPUTER GRAPHICS FORUM 2022年第3期41卷 345-354页

作者： Liu, Huan Zhang, Hui Univ Louisville Comp Sci & Engn Dept Louisville KY 40292 USA

Just as 2D shadows of 3D curves lose structure where lines cross, 3D graphics projections of smooth 4D topological surfaces are interrupted where one surface intersects itself. They twist, turn, and fold back on themselves, leaving important but hidden features behind the surface sheets. In this paper, we propose a smart slicing tool that can read the 4D surface in its entropy map and suggest the optimal way to generate cross-sectional images - or "slices" - of the surface to visualize its underlying 4D structure. Our visualization thinks of a 4D-embedded surface as a collection of 3D curves stacked in time, very much like a flip-book animation, where successive terms in the sequence differ at most by a critical change. This novel method can generate topologically meaningful visualization to depict complex and unfamiliar 4D surfaces, with the minimum number of cross-sectional diagrams. Our approach has been successfully used to create flip-books of diagrams to visualize a range of known 4D surfaces. In this preliminary study, our results show that the new visualization and slicing tool can help the viewers to understand and describe the complex spatial relationships and overall structures of 4D surfaces.

关键词： CCS Concepts • human-centered computing → scientific visualization visualization design and evaluation methods

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Doppler Volume Rendering: A Dynamic, Piecewise Linear Spectral Representation for Visualizing Astrophysics Simulations

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COMPUTER GRAPHICS FORUM 2023年第3期42卷 39-49页

作者： Alghamdi, Reem Mueller, Thomas Jaspe-Villanueva, Alberto Hadwiger, Markus Sadlo, Filip KAUST Thuwal Saudi Arabia Max Planck Inst Astron Heidelberg Germany Heidelberg Univ Heidelberg Germany

We present a novel approach for rendering volumetric data including the Doppler effect of light. Similar to the acoustic Doppler effect, which is caused by relative motion between a sound emitter and an observer, light waves also experience compression or expansion when emitter and observer exhibit relative motion. We account for this by employing spectral volume rendering in an emission-absorption model, with the volumetric matter moving according to an accompanying vector field, and emitting and attenuating light at wavelengths subject to the Doppler effect. By introducing a novel piecewise linearear representation of the involved light spectra, we achieve accurate volume rendering at interactive frame rates. We compare our technique to rendering with traditional point-based spectral representation, and demonstrate its utility using a simulation of galaxy formation.

关键词： CCS Concepts • human-centered computing → scientific visualization • computing methodologies → Simulation evaluation

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LineageD: An Interactive Visual System for Plant Cell Lineage Assignments based on Correctable Machine Learning

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COMPUTER GRAPHICS FORUM 2022年第3期41卷 195-207页

作者： Hong, Jiayi Trubuil, Alain Isenberg, Tobias Univ Paris Saclay INRIA CNRS Paris France Univ Paris Saclay InraE Paris France

We describe LineageD-a hybrid web-based system to predict, visualize, and interactively adjust plant embryo cell lineages. Currently, plant biologists explore the development of an embryo and its hierarchical cell lineage manually, based on a 3D dataset that represents the embryo status at one point in time. This human decision-making process, however, is time-consuming, tedious, and error-prone due to the lack of integrated graphical support for specifying the cell lineage. To fill this gap, we developed a new system to support the biologists in their tasks using an interactive combination of 3D visualization, abstract data visualization, and correctable machine learning to modify the proposed cell lineage. We use existing manually established cell lineages to obtain a neural network model. We then allow biologists to use this model to repeatedly predict assignments of a single cell division stage. After each hierarchy level prediction, we allow them to interactively adjust the machine learning based assignment, which we then integrate into the pool of verified assignments for further predictions. In addition to building the hierarchy this way in a bottom-up fashion, we also offer users to divide the whole embryo and create the hierarchy tree in a top-down fashion for a few steps, improving the ML-based assignments by reducing the potential for wrong predictions. We visualize the continuously updated embryo and its hierarchical development using both 3D spatial and abstract tree representations, together with information about the model's confidence and spatial properties. We conducted case study validations with five expert biologists to explore the utility of our approach and to assess the potential for LineageD to be used in their daily workflow. We found that the visualizations of both 3D representations and abstract representations help with decision making and the hierarchy tree top-down building approach can reduce assignments errors in real practice.

关键词： CCS Concepts • human-centered computing → scientific visualization User interface toolkits

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Thin-Volume visualization on Curved Domains

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COMPUTER GRAPHICS FORUM 2021年第3期40卷 147-157页

作者： Herter, Felix Hege, Hans-Christian Hadwiger, Markus Lepper, Verena Baum, Daniel Zuse Inst Berlin ZIB Dept Visual & Data Centr Comp Berlin Germany King Abdullah Univ Sci & Technol KAUST Thuwal Saudi Arabia Staatliche Museen Berlin Agypt Museum & Papyrussammlung Berlin Germany

Thin, curved structures occur in many volumetric datasets. Their analysis using classical volume rendering is difficult because parts of such structures can bend away or hide behind occluding elements. This problem cannot be fully compensated by effective navigation alone, as structure-adapted navigation in the volume is cumbersome and only parts of the structure are visible in each view. We solve this problem by rendering a spatially transformed view of the volume so that an unobstructed visualization of the entire curved structure is obtained. As a result, simple and intuitive navigation becomes possible. The domain of the spatial transform is defined by a triangle mesh that is topologically equivalent to an open disc and that approximates the structure of interest. The rendering is based on ray-casting, in which the rays traverse the original volume. In order to carve out volumes of varying thicknesses, the lengths of the rays as well as the positions of the mesh vertices can be easily modified by interactive painting under view control. We describe a prototypical implementation and demonstrate the interactive visual inspection of complex structures from digital humanities, biology, medicine, and material sciences. The visual representation of the structure as a whole allows for easy inspection of interesting substructures in their original spatial context. Overall, we show that thin, curved structures in volumetric data can be excellently visualized using ray-casting-based volume rendering of transformed views defined by guiding surface meshes, supplemented by interactive, local modifications of ray lengths and vertex positions.

关键词： CCS Concepts • human-centered computing → scientific visualization visualization techniques • computing methodologies → Rendering

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Visualizing Carotid Blood Flow Simulations for Stroke Prevention

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COMPUTER GRAPHICS FORUM 2021年第3期40卷 435-446页

作者： Eulzer, P. Meuschke, M. Klingner, C. M. Lawonn, K. Univ Jena Fac Math & Comp Sci Jena Germany Univ Magdeburg Dept Simulat & Graph Magdeburg Germany Univ Hosp Jena Clin Neurol Jena Germany

In this work, we investigate how concepts from medical flow visualization can be applied to enhance stroke prevention diagnostics. Our focus lies on carotid stenoses, i.e., local narrowings of the major brain-supplying arteries, which are a frequent cause of stroke. Carotid surgery can reduce the stroke risk associated with stenoses, however, the procedure entails risks itself. Therefore, a thorough assessment of each case is necessary. In routine diagnostics, the morphology and hemodynamics of an afflicted vessel are separately analyzed using angiography and sonography, respectively. Blood flow simulations based on computational fluid dynamics could enable the visual integration of hemodynamic and morphological information and provide a higher resolution on relevant parameters. We identify and abstract the tasks involved in the assessment of stenoses and investigate how clinicians could derive relevant insights from carotid blood flow simulations. We adapt and refine a combination of techniques to facilitate this purpose, integrating spatiotemporal navigation, dimensional reduction, and contextual embedding. We evaluated and discussed our approach with an interdisciplinary group of medical practitioners, fluid simulation and flow visualization researchers. Our initial findings indicate that visualization techniques could promote usage of carotid blood flow simulations in practice.

关键词： CCS Concepts • human-centered computing → scientific visualization • Applied computing → Life and medical sciences

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Parameterized Splitting of Summed Volume Tables

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COMPUTER GRAPHICS FORUM 2021年第3期40卷 123-133页

作者： Reinbold, Christian Westermann, Rudiger Tech Univ Munich Comp Graph & Visualizat Grp Garching Germany

Summed Volume Tables (SVTs) allow one to compute integrals over the data values in any cubical area of a three-dimensional orthogonal grid in constant time, and they are especially interesting for building spatial search structures for sparse volumes. However, SVTs become extremely memory consuming due to the large values they need to store;for a dataset of n values an SVT requires O(nlogn) bits. The 3D Fenwick tree allows recovering the integral values in O(log(3) n) time, at a memory consumption of O(n) bits. We propose an algorithm that generates SVT representations that can flexibly trade speed for memory: From similar characteristics as SVTs, over equal memory consumption as 3D Fenwick trees at significantly lower computational complexity, to even further reduced memory consumption at the cost of raising computational complexity. For a 641 x 9601 x 9601 binary dataset, the algorithm can generate an SVT representation that requires 27.0GB and 46 x 8 data fetch operations to retrieve an integral value, compared to 27.5GB and 1521 x 8 fetches by 3D Fenwick trees, a decrease in fetches of 97%. A full SVT requires 247.6GB and 8 fetches per integral value. We present a novel hierarchical approach to compute and store intermediate prefix sums of SVTs, so that any prescribed memory consumption between O(n) bits and O(nlogn) bits is achieved. We evaluate the performance of the proposed algorithm in a number of examples considering large volume data, and we perform comparisons to existing alternatives.

关键词： CCS Concepts • Information systems → Data structures • human-centered computing → scientific visualization

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Visual Analysis of Electronic Densities and Transitions in Molecules

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COMPUTER GRAPHICS FORUM 2021年第3期40卷 287-298页

作者： Masood, T. Bin Thygesen, S. S. Linares, M. Abrikosov, A. I. Natarajan, V. Hotz, I. Linkoping Univ Dept Sci & Technol ITN Norrkoping Sweden Linkoping Univ Lab Organ Elect Norrkoping Sweden Indian Inst Sci Bangalore Karnataka India

The study of electronic transitions within a molecule connected to the absorption or emission of light is a common task in the process of the design of new materials. The transitions are complex quantum mechanical processes and a detailed analysis requires a breakdown of these processes into components that can be interpreted via characteristic chemical properties. We approach these tasks by providing a detailed analysis of the electron density field. This entails methods to quantify and visualize electron localization and transfer from molecular subgroups combining spatial and abstract representations. The core of our method uses geometric segmentation of the electronic density field coupled with a graph-theoretic formulation of charge transfer between molecular subgroups. The design of the methods has been guided by the goal of providing a generic and objective analysis following fundamental concepts. We illustrate the proposed approach using several case studies involving the study of electronic transitions in different molecular systems.

关键词： CCS Concepts • human-centered computing → scientific visualization visualization techniques • Applied computing → Chemistry

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An Interactive Approach for Identifying Structure Definitions

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COMPUTER GRAPHICS FORUM 2022年第3期41卷 321-332页

作者： Mikula, Natalia Doerffel, Tom Baum, Daniel Hege, Hans-Christian Zuse Inst Berlin ZIB Berlin Germany Free Univ Berlin Berlin Germany

Our ability to grasp and understand complex phenomena is essentially based on recognizing structures and relating these to each other. For example, any meteorological description of a weather condition and explanation of its evolution recurs to meteorological structures, such as convection and circulation structures, cloud fields and rain fronts. All of these are spatiotemporal structures, defined by time-dependent patterns in the underlying fields. Typically, such a structure is defined by a verbal description that corresponds to the more or less uniform, often somewhat vague mental images of the experts. However, a precise, formal definition of the structures or, more generally, of the concepts is often desirable, e.g., to enable automated data analysis or the development of phenomenological models. Here, we present a systematic approach and an interactive tool to obtain formal definitions of spatiotemporal structures. The tool enables experts to evaluate and compare different structure definitions on the basis of data sets with time-dependent fields that contain the respective structure. Since structure definitions are typically parameterized, an essential part is to identify parameter ranges that lead to desired structures in all time steps. In addition, it is important to allow a quantitative assessment of the resulting structures simultaneously. We demonstrate the use of the tool by applying it to two meteorological examples: finding structure definitions for vortex cores and center lines of temporarily evolving tropical cyclones. Ideally, structure definitions should be objective and applicable to as many data sets as possible. However, finding such definitions, e.g., for the common atmospheric structures in meteorology, can only be a long-term goal. The proposed procedure, together with the presented tool, is just a first systematic approach aiming at facilitating this long and arduous way.

关键词： CCS Concepts • computing methodologies → Modeling methodologies • human-centered computing → scientific visualization Visual analytics • Applied computing → Earth and atmospheric sciences

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