Computer Graphics & Visual Computing (CGVC) 2016

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    CGVC 2016: Frontmatter
    (Eurographics Association, 2016) Cagatay Turkay; Tao Ruan Wan; Cagatay Turkay and Tao Ruan Wan
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    Topological Visualisation Techniques for the Understanding of Lattice Quantum Chromodynamics (LQCD) Simulations
    (The Eurographics Association, 2016) Thomas, Dean P.; Borgo, Rita; Hands, Simon; Cagatay Turkay and Tao Ruan Wan
    The use of topology for visualisation applications has become increasingly popular due to its ability to summarise data at a high level. Criticalities in scalar field data are used by visualisation methods such as the Reeb graph and contour trees to present topological structure in simple graph based formats. These techniques can be used to segment the input field, recognising the boundaries between multiple objects, allowing whole contour meshes to be seeded as separate objects. In this paper we demonstrate the use of topology based techniques when applied to theoretical physics data generated from Quantum Chromodynamics simulations, which due to its structure complicates their use. We also discuss how the output of algorithms involved in topological visualisation can be used by physicists to further their understanding of Quantum Chromodynamics.
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    Tactile Mesh Saliency: A Brief Synopsis
    (The Eurographics Association, 2016) Lau, Manfred; Dev, Kapil; Cagatay Turkay and Tao Ruan Wan
    This work has previously been published [LDS 16] and this extended abstract provides a synopsis for further discussion at the UK CGVC 2016 conference. We introduce the concept of tactile mesh saliency, where tactile salient points on a virtual mesh are those that a human is more likely to grasp, press, or touch if the mesh were a real-world object. We solve the problem of taking as input a 3D mesh and computing the tactile saliency of every mesh vertex. The key to solving this problem is in a new formulation that combines deep learning and learning-to-rank methods to compute a tactile saliency measure. Finally, we discuss possibilities for future work.
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    MLCut: Exploring Multi-Level Cuts in Dendrograms for Biological Data
    (The Eurographics Association, 2016) Vogogias, Athanasios; Kennedy, Jessie; Archambault, Daniel; Smith, V. Anne; Currant, Hannah; Cagatay Turkay and Tao Ruan Wan
    Choosing a single similarity threshold for cutting dendrograms is not sufficient for performing hierarchical clustering analysis of heterogeneous data sets. In addition, alternative automated or semi-automated methods that cut dendrograms in multiple levels make assumptions about the data in hand. In an attempt to help the user to find patterns in the data and resolve ambiguities in cluster assignments, we developed MLCut: a tool that provides visual support for exploring dendrograms of heterogeneous data sets in different levels of detail. The interactive exploration of the dendrogram is coordinated with a representation of the original data, shown as parallel coordinates. The tool supports three analysis steps. Firstly, a single-height similarity threshold can be applied using a dynamic slider to identify the main clusters. Secondly, a distinctiveness threshold can be applied using a second dynamic slider to identify ''weak-edges'' that indicate heterogeneity within clusters. Thirdly, the user can drill-down to further explore the dendrogram structure - always in relation to the original data - and cut the branches of the tree at multiple levels. Interactive drill-down is supported using mouse events such as hovering, pointing and clicking on elements of the dendrogram. Two prototypes of this tool have been developed in collaboration with a group of biologists for analysing their own data sets. We found that enabling the users to cut the tree at multiple levels, while viewing the effect in the original data, is a promising method for clustering which could lead to scientific discoveries.
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    Fire and Gas Detection Mapping using Volumetric Rendering
    (The Eurographics Association, 2016) Cotterill, Cameron; Davison, Tyrone; O'Connor, Simon J.; Orr, David; Charles, Fred; Tang, Wen; Cagatay Turkay and Tao Ruan Wan
    The software presented here provides an interactive real-time tool for the simulation of fire and gas detection mapping using volumetric rendering based on the layouts of fire and gas detectors within 3D virtual environments.
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    Collaborative Computational Projects - Visualisation Applications Survey
    (The Eurographics Association, 2016) Turner, Martin J.; Fowler, Ron; Morris, Tim; Cagatay Turkay and Tao Ruan Wan
    This extended abstract presents initial outcomes from three visualisation user needs surveys, and includes an invitation for new communities to engage with follow-on surveys. Statistical and text cluster analysis have been used to assist specific computational groups; in order to select certain visualisation application packages for software development and to select which new algorithms to implement. This analysis is now also available for advising and creating recommendations to build a long term visualisation support service. The focus of these surveys and this work has been on looking at the use of software toolkits and application packages rather then surveying specific visualisation algorithm techniques.
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    Hybrid Data-Parallel Contour Tree Computation
    (The Eurographics Association, 2016) Carr, Hamish; Sewell, Christopher; Lo, Li-Ta; Ahrens, James; Cagatay Turkay and Tao Ruan Wan
    As data sets increase in size beyond the petabyte, it is increasingly important to have automated methods for data analysis and visualisation. While topological analysis tools such as the contour tree and Morse-Smale complex are now well established, there is still a shortage of efficient parallel algorithms for their computation, in particular for massively data-parallel computation on a SIMD model. We report the first data-parallel algorithm for computing the fully augmented contour tree, using a quantised computation model. We then extend this to provide a hybrid data-parallel / distributed algorithm allowing scaling beyond a single GPU or CPU, and provide results for its computation. Our implementation uses the portable data-parallel primitives provided by NVIDIA's Thrust library, allowing us to compile our same code for both GPUs and multi-core CPUs.
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    Amplitude Modulated Line-Based Halftoning
    (The Eurographics Association, 2016) Ahmed, Abdalla G. M.; Deussen, Oliver; Cagatay Turkay and Tao Ruan Wan
    We present a new approach for line-based halftoning of images, where banks of waveforms are modulated by the gray levels of the rendered image. We present examples that employ sinusoidal and triangular waveforms, and highlight some applications, including stylized rendering, halftoning in line-based devices, and education.
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    A Calibrated Olfactory Display for High Fidelity Virtual Environments
    (The Eurographics Association, 2016) Dhokia, Amar; Doukakis, Efstratious; Asadipour, Ali; Harvey, Carlo; Bashford-Rogers, Thomas; Debattista, Kurt; Waterfield, Brian; Chalmers, Alan; Cagatay Turkay and Tao Ruan Wan
    Olfactory displays provide a means to reproduce olfactory stimuli for use in virtual environments. Many of the designs produced by researchers, strive to provide stimuli quickly to users and focus on improving usability and portability, yet concentrate less on providing high levels of accuracy to improve the fidelity of odour delivery. This paper provides the guidance to build a reproducible and low cost olfactory display which is able to provide odours to users in a virtual environment at accurate concentration levels that are typical in everyday interactions; this includes ranges of concentration below parts per million and into parts per billion. This paper investigates build concerns of the olfactometer and its proper calibration in order to ensure concentration accuracy of the device. An analysis is provided on the recovery rates of a specific compound after excitation. This analysis provides insight into how this result can be generalisable to the recovery rates of any volatile organic compound, given knowledge of the specific vapour pressure of the compound.
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    Selective BRDFs for High Fidelity Rendering
    (The Eurographics Association, 2016) Bradley, Tim; Debattista, Kurt; Bashford-Rogers, Thomas; Harvey, Carlo; Doukakis, Stratos; Chalmers, Alan; Cagatay Turkay and Tao Ruan Wan
    High fidelity rendering systems rely on accurate material representations to produce a realistic visual appearance. However, these accurate models can be slow to evaluate. This work presents an approach for approximating these high accuracy reflectance models with faster, less complicated functions in regions of an image which possess low visual importance. A subjective rating experiment was conducted in which thirty participants were asked to assess the similarity of scenes rendered with low quality reflectance models, a high quality data-driven model and saliency based hybrids of those images. In two out of the three scenes that were evaluated significant differences were not found between the hybrid and reference images. This implies that in less visually salient regions of an image computational gains can be achieved by approximating computationally expensive materials with simpler analytic models.
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    Improving and Optimising Visualisations of Full-waveform LiDAR Data
    (The Eurographics Association, 2016) Miltiadou, Milto; Campbell, Neill D. F.; Brown, Matthew; Cosker, Darren; Grant, Michael; Cagatay Turkay and Tao Ruan Wan
    Visualisations of Remotely Sensed data has a significant role in forestry. Foresters have a great knowledge about forests (for example they can identify tree diseases) and they can derive a wealth of information directly from visualisations, saving the travelling time and cost of getting into the forests.
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    Towards Analytical Provenance Visualization for Criminal Intelligence Analysis
    (The Eurographics Association, 2016) Islam, Junayed; Anslow, Craig; Xu, Kai; Wong, William; Zhang, Leishi; Cagatay Turkay and Tao Ruan Wan
    In criminal intelligence analysis to complement the information entailed and to enhance transparency of the operations, it demands logs of the individual processing activities within an automated processing system. Management and tracing of such security sensitive analytical information flow originated from tightly coupled visualizations into visual analytic system for criminal intelligence that triggers huge amount of analytical information on a single click, involves design and development challenges. To lead to a believable story by using scientific methods, reasoning for getting explicit knowledge of series of events, sequences and time surrounding interrelationships with available relevant information by using human perception, cognition, reasoning with database operations and computational methods, an analytic visual judgmental support is obvious for criminal intelligence. Our research outlines the requirements and development challenges of such system as well as proposes a generic way of capturing different complex visual analytical states and processes known as analytic provenance. The proposed technique has been tested into a large heterogeneous event-driven visual analytic modular analyst’'s user interface (AUI) of the project VALCRI (Visual Analytics for Sensemaking in Criminal Intelligence) and evaluated by the police intelligence analysts through it's visual state capturing and retracing interfaces. We have conducted several prototype evaluation sessions with the groups of end-users (police intelligence analysts) and found very positive feedback. Our approach provides a generic support for visual judgmental process into a large complex event-driven AUI system for criminal intelligence analysis.
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    PED: Pedestrian Environment Designer
    (The Eurographics Association, 2016) McIlveen, James; Maddock, Steve; Heywood, Peter; Richmond, Paul; Cagatay Turkay and Tao Ruan Wan
    Pedestrian simulations have many uses, from pedestrian planning for architecture design through to games and entertainment. However, it is still challenging to efficiently author such simulations, especially for non-technical users. Direct pedestrian control is usually laborious, and, while indirect, environment-level control is often faster, it currently lacks the necessary tools to create complex environments easily and without extensive prior technical knowledge. This paper describes an indirect, environment-level control system in which pedestrians' behaviour can be specified efficiently and then interactively tuned. With the Pedestrian Environment Designer (PED) interface, authors can define environments using tools similar to those found in raster graphics editing software such as PhotoshopTM. Users paint on two-dimensional bitmap layers to control the behaviour of pedestrians in a three-dimensional simulation. The layers are then compiled to produce a live, agent-based pedestrian simulation using the FLAME GPU framework. Entrances and exits can be inserted, collision boundaries defined, and areas of attraction and avoidance added. The system also offers dynamic simulation updates at runtime giving immediate author feedback and enabling authors to simulate scenarios with dynamic elements such as barriers, or dynamic circumstances such as temporary areas of avoidance. As a result, authors are able to create complex crowd simulations more effectively and with minimal training.
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    Volumetric Spot Noise for Procedural 3D Shell Texture Synthesis
    (The Eurographics Association, 2016) Pavie, Nicolas; Gilet, Guillaume; Dischler, Jean-Michel; Galin, Eric; Ghazanfarpour, Djamchid; Cagatay Turkay and Tao Ruan Wan
    In this paper, we present an extension of the Locally Controlled Spot Noise and a visualization pipeline for volumetric fuzzy details synthesis. We extend the noise model to author volumetric fuzzy details using filtered 3D quadratic kernel functions convolved with a projective non-uniform 2D distribution of impulses. We propose a new method based on order independent splatting to compute a fast view dependent approximation of shell noise at interactive rates. Our method outperforms ray marching techniques and avoids aliasing artifacts, thus improving interactive content authoring feedback. Moreover, generated surface details share the same properties as procedural noise: they extend on potentially infinite surfaces, are defined in an extremely compact way, are non-repetitive, continuous (no discrete voxel-artifacts when zooming) and independent of the definition of the underlying surface (no surface parameterization is required).
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    MolPathFinder: Interactive Multi-Dimensional Path Filtering of Molecular Dynamics Simulation Data
    (The Eurographics Association, 2016) Alharbi, Naif; Laramee, Robert S.; Chavent, Matthieu; Cagatay Turkay and Tao Ruan Wan
    Molecular Dynamics Simulations (MDS) play an important role in the field of computational biology. The simulations produce large high-dimensional, spatio-temporal data describing the motion of atoms and molecules. A central challenge in the field is the extraction and visualization of useful behavioral patterns from these simulations. Many visualization tools have been proposed to help computational biologists gain insight into MDS data. While recent developments focused on accelerating and optimising the rendering, it is still necessary to design new metaphors to better understand and filter MDS datasets. In this article, we are describing a set of tools to interactively filter and highlight dynamic and complex paths constituted by motions of molecules. In collaboration with computational biologists, we have tested our approach on large-scale, real data. Based on the user's feedback, our program helped scientists to navigate more easily through their dataset and isolate interesting patterns. Furthermore, our approach was useful to investigate both local and global behavior of molecular motions.
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    TimeSets for Uncertainty Visualisation
    (The Eurographics Association, 2016) Salisu, Saminu; Xu, Kai; Wagstaff, Adrian; Biggs, Mike; Phillips, Graham; Cagatay Turkay and Tao Ruan Wan
    TimeSets consist of a timeline showing sequence of events displayed across a visualisation, while makings sense of sets relation among events in the timeline [NXWW15]. This study looked into extending TimeSets to accommodate Visualisation of trust and uncertainty as parts of its variables for events displayed across the timeline. The aim of the challenge is to build tools in the context of big data analytics that can be used to aid military operations through intelligence analytics and decision-making.
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    Generating Watertight Isosurfaces from 3D Seismic Data
    (The Eurographics Association, 2016) Khan, Muhammad Sulaiman; Carr, Hamish; Angus, Doug; Cagatay Turkay and Tao Ruan Wan
    Seismic data visualisation and analysis is an area of research interest for a lot of commercial and academic disciplines. It enables the geoscientists to understand structures underneath the earth. It is an important step in building subsurface geological models to identify hydrocarbon reservoirs and running geological simulations. Good quality watertight surface meshes are required for constructing these models for accurate identification and extraction of strata/horizons that contain carbon deposits such as fuel and gas. This research demonstrates extracting watertight geometric surfaces from 3D seismic volumes to improve horizon identification and extraction. Isosurfaces and Fiber Surfaces are proposed for extracting horizons from seismic data. Initial tests with isosurfaces have been conducted and further experiments using fiber furfaces are underway as next direction and discussed in sections 4.5 and 4.6.
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    Interactive GPU-based Image Deformation for Mobile Devices
    (The Eurographics Association, 2016) Vollmer, Jan Ole; Trapp, Matthias; Döllner, Jürgen; Cagatay Turkay and Tao Ruan Wan
    Interactive image deformation is an important feature of modern image processing pipelines. It is often used to create caricatures and animation for input images, especially photos. State-of-the-art image deformation techniques are based on transforming vertices of a mesh, which is textured by the input image, using affine transformations such as translation, and scaling. However, the resulting visual quality of the output image depends on the geometric resolution of the mesh. Performing these transformations on the CPU often further inhibits performance and quality. This is especially problematic on mobile devices where the limited computational power reduces the maximum achievable quality. To overcome these issue, we propose the concept of an intermediate deformation buffer that stores deformation information at a resolution independent of the mesh resolution. This allows the combination of a high-resolution buffer with a low-resolution mesh for interactive preview, as well as a high-resolution mesh to export the final image. Further, we present a fully GPU-based implementation of this concept, taking advantage of modern OpenGL ES features, such as compute shaders.
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    Using Semi-automatic 3D Scene Reconstruction to Create a Digital Medieval Charnel Chapel
    (The Eurographics Association, 2016) Shui, Wuyang; Maddock, Steve; Heywood, Peter; Craig-Atkins, Elizabeth; Crangle, Jennifer; Hadley, Dawn; Scott, Rab; Cagatay Turkay and Tao Ruan Wan
    The use of a terrestrial laser scanner (TLS) has become a popular technique for the acquisition of 3D scenes in the fields of cultural heritage and archaeology. In this study, a semi-automatic reconstruction technique is presented to convert the point clouds that are produced, which often contain noise or are missing data, into a set of triangle meshes. The technique is applied to the reconstruction of a medieval charnel chapel. To reduce the computational complexity of reconstruction, the point cloud is first segmented into several components guided by the geometric structure of the scene. Landmarks are interactively marked on the point cloud and multiple cutting planes are created using the least squares method. Then, sampled point clouds for each component are meshed by ball-pivoting. In order to fill the large missing regions on the walls and ground plane, inserted triangle meshes are calculated on the basis of the convex hull of the projection points on the bounding plane. The iterative closest point (ICP) approach and local non-rigid registration methods are used to make the inserted triangle meshes and original model tightly match. Using these methods, we have reconstructed a digital model of the medieval charnel chapel, which not only serves to preserve a digital record of it, but also enables members of t he public to experience the space virtually.
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    Exploring Face Recognition under Complex Lighting Conditions with HDR Imaging
    (The Eurographics Association, 2016) Ige, Emmanuel O.; Debattista, Kurt; Muhkerjee, Ratnajit; Chalmers, Alan; Cagatay Turkay and Tao Ruan Wan
    Applying image processing applications under complex or harsh lighting conditions can be a difficult challenge. In particular, face recognition can be prone to such limitations due to the uncontrolled nature of the applications to which it is applied. One of the conventional ways used to resolve this concern is by capturing images under controlled light or pre-processing the affected images, which can change the perception of the resultant images. One of the primary issues with this is the lack of information present in the original images due to over-exposed and under-exposed pixels. High Dynamic Range (HDR) imaging offers an alternative due to its capability of handling natural lighting. This paper explores the use HDR imaging for face recognition. A training and testing set of HDR images under different harsh lighting conditions was created. Traditional low dynamic range methods were compared with using the full range and applying HDR methods to a traditional face recognition method. Results demonstrate that adapting HDR captured images for use with traditional face recognition methods via a tone mapping provides sufficient improvement and enables traditional algorithms to cope well with harsh lighting scenarios.