Papers by Anders Ynnerman
Communications of the ACM, 2016
A full-body virtual autopsy of an ancient Egyptian mummy showed visitors he was likely murdered.
Computer Graphics Forum, Oct 10, 2013
Interactive volume rendering in its standard formulation has become an increasingly important too... more Interactive volume rendering in its standard formulation has become an increasingly important tool in many application domains. In recent years several advanced volumetric illumination techniques to be used in interactive scenarios have been proposed. These techniques claim to have perceptual benefits as well as being capable of producing more realistic volume rendered images. Naturally, they cover a wide spectrum of illumination effects, including varying shading and scattering effects. In this survey, we review and classify the existing techniques for advanced volumetric illumination. The classification will be conducted based on their technical realization, their performance behavior as well as their perceptual capabilities. Based on the limitations revealed in this review, we will define future challenges in the area of interactive advanced volumetric illumination.
Foundations of Data Visualization, 2020
Research has shown that learning outcomes can be improved by interactive visualization and explor... more Research has shown that learning outcomes can be improved by interactive visualization and exploration. This has led to the appearance of interactive installations on a range of platforms from handheld devices to large immersive dome theaters. One of the underlying principles of this data-driven visualization for broad audiences is the notion of the confluence of exploratory and explanatory visualization into the concept of "Exploranation," meaning that explanation and exploration converge in the same application. However, it is necessary to apply specific visualization and interaction design principles to enable engaging storytelling and user-driven discovery in interactive installations targeting a general audience. The design principles are unique for different platforms and uses. We here present an account for some results, challenges and areas in need for further research. We also describe a set of different cases in which visualization has been used to reach broad audiences. Based on the examples, lessons learned are described and general principles and recommendations are provided. Visual representations have traditionally played a fundamental role in the quest to convey knowledge about the content of museum collections containing items such as rare historical artifacts or valuable pieces of art. They also serve a purpose in framing events such as the narratives of pivotal moments in human history. In science centers, visualization, and particularly interactive visualization, is one of the core technologies in the illustration of scientific knowledge, major findings and method-
Computer Graphics Forum, 2021
We present a state‐of‐the‐art report on visualization in astrophysics. We survey representative p... more We present a state‐of‐the‐art report on visualization in astrophysics. We survey representative papers from both astrophysics and visualization and provide a taxonomy of existing approaches based on data analysis tasks. The approaches are classified based on five categories: data wrangling, data exploration, feature identification, object reconstruction, as well as education and outreach. Our unique contribution is to combine the diverse viewpoints from both astronomers and visualization experts to identify challenges and opportunities for visualization in astrophysics. The main goal is to provide a reference point to bring modern data analysis and visualization techniques to the rich datasets in astrophysics.
Vessel segmentation is an important prerequisite for many medical applications. While automatic v... more Vessel segmentation is an important prerequisite for many medical applications. While automatic vessel segmentation is an active field of research, interaction and visualization techniques for semi ...
Kinetic modeling is the tool of choice when developing new positron emission tomography (PET) tra... more Kinetic modeling is the tool of choice when developing new positron emission tomography (PET) tracers for quantitative functional analysis. Several approaches are widely used to facilitate this pro ...
We present an interactive visual environment for linked analysis of brain imaging and clinical me... more We present an interactive visual environment for linked analysis of brain imaging and clinical measurements. The environment is developed in an iterative participatory design process involving neur ...
IEEE Transactions on Visualization and Computer Graphics, 2019
The complexity of today's visualization applications demands specific visualization systems tailo... more The complexity of today's visualization applications demands specific visualization systems tailored for the development of these applications. Frequently, such systems utilize levels of abstraction to improve the application development process, for instance by providing a data flow network editor. Unfortunately, these abstractions result in several issues, which need to be circumvented through an abstraction-centered system design. Often, a high level of abstraction hides low level details, which makes it difficult to directly access the underlying computing platform, which would be important to achieve an optimal performance. Therefore, we propose a layer structure developed for modern and sustainable visualization systems allowing developers to interact with all contained abstraction levels. We refer to this interaction capabilities as usage abstraction levels, since we target application developers with various levels of experience. We formulate the requirements for such a system, derive the desired architecture, and present how the concepts have been exemplary realized within the Inviwo visualization system. Furthermore, we address several specific challenges that arise during the realization of such a layered architecture, such as communication between different computing platforms, performance centered encapsulation, as well as layer-independent development by supporting cross layer documentation and debugging capabilities.
Computer Graphics Forum, 2017
In this work, we address the challenge of seamlessly visualizing astronomical data exhibiting hug... more In this work, we address the challenge of seamlessly visualizing astronomical data exhibiting huge scale differences in distance, size, and resolution. One of the difficulties is accurate, fast, and dynamic positioning and navigation to enable scaling over orders of magnitude, far beyond the precision of floating point arithmetic. To this end we propose a method that utilizes a dynamically assigned frame of reference to provide the highest possible numerical precision for all salient objects in a scene graph. This makes it possible to smoothly navigate and interactively render, for example, surface structures on Mars and the Milky Way simultaneously. Our work is based on an analysis of tracking and quantification of the propagation of precision errors through the computer graphics pipeline using interval arithmetic. Furthermore, we identify sources of precision degradation, leading to incorrect object positions in screen‐space and z‐fighting. Our proposed method operates without nea...
IEEE transactions on visualization and computer graphics, 2017
We present a method for interactive global illumination of both static and time-varying volumetri... more We present a method for interactive global illumination of both static and time-varying volumetric data based on reduction of the overhead associated with re-computation of photon maps. Our method uses the identification of photon traces invariant to changes of visual parameters such as the transfer function (TF), or data changes between time-steps in a 4D volume. This lets us operate on a variant subset of the entire photon distribution. The amount of computation required in the two stages of the photon mapping process, namely tracing and gathering, can thus be reduced to the subset that are affected by a data or visual parameter change. We rely on two different types of information from the original data to identify the regions that have changed. A low resolution uniform grid containing the minimum and maximum data values of the original data is derived for each time step. Similarly, for two consecutive time-steps, a low resolution grid containing the difference between the overla...
Computer Graphics Forum, 2016
A central topic in scientific visualization is the transfer function (TF) for volume rendering. T... more A central topic in scientific visualization is the transfer function (TF) for volume rendering. The TF serves a fundamental role in translating scalar and multivariate data into color and opacity to express and reveal the relevant features present in the data studied. Beyond this core functionality, TFs also serve as a tool for encoding and utilizing domain knowledge and as an expression for visual design of material appearances. TFs also enable interactive volumetric exploration of complex data. The purpose of this state‐of‐the‐art report (STAR) is to provide an overview of research into the various aspects of TFs, which lead to interpretation of the underlying data through the use of meaningful visual representations. The STAR classifies TF research into the following aspects: dimensionality, derived attributes, aggregated attributes, rendering aspects, automation, and user interfaces. The STAR concludes with some interesting research challenges that form the basis of an agenda fo...
Eurographics Workshop on Parallel Graphics and Visualization, 2012
A major challenge when designing general purpose graphics hardware is to allow efficient access t... more A major challenge when designing general purpose graphics hardware is to allow efficient access to texture data. Although different rendering paradigms vary with respect to their data access patterns, there is no flexibility when it comes to data caching provided by the graphics architecture. In this paper we focus on volume ray-casting, and show the benefits of algorithm-aware data caching. Our Marching Caches method exploits inter-ray coherence and thus utilizes the memory layout of the highly parallel processors by allowing them to share data through a cache which marches along with the ray front. By exploiting Marching Caches we can apply higher-order reconstruction and enhancement filters to generate more accurate and enriched renderings with an improved rendering performance. We have tested our Marching Caches with seven different filters, e. g., Catmul-Rom, Bspline, ambient occlusion projection, and could show that a speed up of four times can be achieved compared to using the caching implicitly provided by the graphics hardware, and that the memory bandwidth to global memory can be reduced by orders of magnitude. Throughout the paper, we will introduce the Marching Cache concept, provide implementation details and discuss the performance and memory bandwidth impact when using different filters.
Enabling Haptic Interaction with Volumetric MRI Data Through Knowledge-based Tissue Separation
International Conference on Computer Graphics and Interactive Techniques, 2006
Computational Visual Media, 2016
Processing and visualizing large scale volumetric and geometric datasets is mission critical in a... more Processing and visualizing large scale volumetric and geometric datasets is mission critical in an increasing number of applications in academic research as well as in commercial enterprise. Often the datasets are, or can be processed to become, sparse. In this paper, we present VoxLink, a novel approach to render sparse volume data in a memory-efficient manner enabling interactive rendering on common, offthe-shelf graphics hardware. Our approach utilizes current GPU architectures for voxelizing, storing, and visualizing such datasets. It is based on the idea of perpixel linked lists (ppLL), an A-buffer implementation for order-independent transparency rendering. The method supports voxelization and rendering of dense semi-transparent geometry, sparse volume data, and implicit surface representations with a unified data structure. The proposed data structure also enables efficient simulation of global lighting effects such as reflection, refraction, and shadow ray evaluation.
Extending and Simplifying Transfer Function Design in Medical Volume Rendering Using Local Histograms
Joint Eurographics - IEEE TCVG Symposium on Visualization, 2005
Direct Volume Rendering (DVR) is known to be of diagnostic value in the analysis of medical data ... more Direct Volume Rendering (DVR) is known to be of diagnostic value in the analysis of medical data sets. However, its deployment in everyday clinical use has so far been limited. Two major challenges are that the current methods for Transfer Function (TF) construction are too complex and that the tissue separation abilities of the TF need to be extended. In
Proceedings. Eighth International Conference on Information Visualisation, 2004. IV 2004.
When planning a Leksell GammaKnife R treatment, dose planners place iso-centres of the irradiatio... more When planning a Leksell GammaKnife R treatment, dose planners place iso-centres of the irradiation field in such a way that a certain iso-dose surface conforms as closely as possible to a target, such as a tumour. Today this planning is done primarily in 2D, and the clinician places the iso-centres onto the currentmedical image. The images used are usually acquired by MRI, CT or Angiography. In this paper we investigate the use of interactive 3D visualization and haptics to perform the dose planning. In a pilot implementation we provide the user with a virtual environment with real-time graphics to visualize the target, surrounding tissue and iso-dose surfaces as well as an integrated graphical user interface. The overall aim of the implementation is to increase the efficiency and precision of the planning process by adding haptic feedback to represent various constraints and opportunities in the planning process and so guide the user to an optimal placement of the iso-centres. Preliminary feedback from potential users has been very positive.
First Joint Eurohaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems
We present a general, proxy-based approach to volume haptics founded upon the notion of 'haptic p... more We present a general, proxy-based approach to volume haptics founded upon the notion of 'haptic primitives'. Haptic modes each representing a different aspect of volumetric data, are created by defining sets of haptic primitives which reflect the local properties of the data. The proxy position for every time-frame in the haptic loop is found by balancing the force feedback in the haptic instrument with the force from the haptic primitives involved. The presented general framework allows for rapid development of haptic feedback modes for volumetric data. The approach also allows, in contrast to previous work on proxy-based volume haptics, combination of non-orthogonal constraints and thus allows free combination of various modes in haptic exploration of multivariate data. We demonstrate the effectiveness of our approach through the implementation of five different haptic modes.
Lecture Notes in Computer Science, 2013
Diffusion Tensor Imaging (DTI) in combination with fiber tracking algorithms enables visualizatio... more Diffusion Tensor Imaging (DTI) in combination with fiber tracking algorithms enables visualization and characterization of white matter structures in the brain. However, the low spatial resolution associated with the inherently low signal-to-noise ratio of DTI has raised concerns regarding the reliability of the obtained fiber bundles. Therefore, recent advancements in fiber tracking algorithms address the accuracy of the reconstructed fibers. In this paper, we propose a novel approach for analyzing and reducing the uncertainty of densely sampled 3D DTI fibers in biological specimens. To achieve this goal, we derive the uncertainty in the reconstructed fiber tracts using different deterministic and stochastic fiber tracking algorithms. Through a unified representation of the derived uncertainty, we generate a new set of reconstructed fiber tracts that has a lower level of uncertainty. We will discuss our approach in detail and present the results we could achieve when applying it to several use cases.
We present a direct interblock interpolation technique that enables direct volume rendering of bl... more We present a direct interblock interpolation technique that enables direct volume rendering of blocked, multireso- lution volumes. The proposed method smoothly interpolates between blocks of arbitrary block-wise level-of-detail (LOD) without sample replication or padding. This permits extreme changes in resolution across block boundaries and removes the interblock dependency for the LOD creation process. In addition the full data reduction from the LOD selection can be maintained throughout the rendering pipeline. Our rendering pipeline employs a flat block subdivision followed by a transfer function based adaptive LOD scheme. We demonstrate the effectiveness of our method by rendering volumes of the order of gigabytes using consumer graphics cards on desktop PC systems.
Volume Graphics, 2010
We present a novel approach to interactive and concurrent volume visualization of functional Magn... more We present a novel approach to interactive and concurrent volume visualization of functional Magnetic Resonance Imaging (fMRI). While the patient is in the scanner, data is extracted in real-time using state-of-the-art signal processing techniques. The fMRI signal is treated as light emission when rendering a patient-specific high resolution reference MRI volume, obtained at the beginning of the experiment. As a result, the brain glows and emits light from active regions. The low resolution fMRI signal is thus effectively fused with the reference brain with the current transfer function settings yielding an effective focus and context visualization. The delay from a change in the fMRI signal to the visualization is approximately 2 seconds. The advantage of our method over standard 2D slice based methods is shown in a user study. We demonstrate our technique through experiments providing interactive visualization to the fMRI operator and also to the test subject in the scanner through a head mounted display.
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Papers by Anders Ynnerman