Category Archives: Computer Graphics Forum

About EuroVis 2014 at Swansea University

Eurovis 2014EuroVis 2014, hosted by Swansea University in the UK, was the
16th annual visualization gathering organized by the EuroGraphics Working
Group on Data Visualization and supported by the Visualization and Graphics
Technical Committee (VGTC). EuroVis has been a EuroGraphics and VGTC
co-supported international visualization symposium held in Europe annually
since 1999. In 2012 EuroVis graduated to a conference. The conference
attracted 258 delegate from 25 countries throughout the world.

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Eurographics 2013 Best Paper Award

splitprismWe are pleased to announce our award of Best Paper at Eurographics 2013 for our paper Photon Parameterisation for Robust Relaxation Constraints, Ben Spencer and Mark W. Jones. [Link to paper]

The paper introduces a technique that augments each photon with information about its origin trajectory. Using this, lighting is separable during density estimation queries. Additionally, we spot fine edge detail using PCA allowing us to employ photon relaxation without detrimental effects. This results in high qualify photon maps that reduce variance and can be rendered with very low bandwidth kernels reducing bias. [Link to news on]

Photon Parameterisation for Robust Relaxation Constraints

splitprismThis paper presents a novel approach to detecting and preserving fine illumination structure within photon maps. Data derived from each photon’s primal trajectory is encoded and used to build a high-dimensional kd-tree. Incorporation of these new parameters allows for precise differentiation between intersecting ray envelopes, thus minimizing detail degradation when combined with photon relaxation. We demonstrate how parameter-aware querying is beneficial in both detecting and removing noise. We also propose a more robust structure descriptor based on principal components analysis that better identifies anisotropic detail at the sub-kernel level.We illustrate the effectiveness of our approach in several example scenes and show significant improvements when rendering complex caustics compared to previous methods.

pdficon_largeBen Spencer and Mark W. Jones
Computer Graphics Forum, Volume 32, Issue 2pt1, pages 83–92, May 2013. [doi]

Best paper, Eurographics 2013.

InK-Compact: In-Kernel Stream Compaction and Its Application to Multi-Kernel Data Visualization on General-Purpose GPUs

inkcompactStream compaction is an important parallel computing primitive that produces a reduced (compacted) output stream consisting of only valid elements from an input stream containing both invalid and valid elements. Computing on this compacted stream rather than the mixed input stream leads to improvements in performance, load balancing, and memory footprint. Stream compaction has numerous applications in a wide range of domains: e.g., deferred shading, isosurface extraction, and surface voxelization in computer graphics and visualization. We present a novel In-Kernel stream compaction method, where compaction is completed before leaving an operating kernel. This contrasts with conventional parallel compaction methods that require leaving the kernel and running a prefix sum kernel followed by a scatter kernel. We apply our compaction methods to ray-tracing-based visualization of volumetric data. We demonstrate that the proposed In-Kernel Compaction outperforms the standard out-of-kernel Thrust parallel-scan method for performing stream compaction in this real-world application. For the data visualization, we also propose a novel multi-kernel ray-tracing pipeline for increased thread coherency and show that it outperforms a conventional single-kernel approach.

D. M.pdficon_large Hughes, I. S. Lim, M. W. Jones, A. Knoll and B. Spencer
Computer Graphics Forum, 2013, 32(6), 178-188. [doi]

Image wins 2013 Computer Graphics Forum cover competition


Winning image for Computer Graphics Forum cover competition 2013

Ben Spencer and Mark W. Jones have again won the Computer Graphics Forum cover competition. The winning image will be used throughout 2013 as the front cover image of the journal Computer Graphics Forum. The image shows a visualisation of the parameter space of photon trajectory from the emitting light source. When encoded into the photon map, this can be used to distinguish overlapping light envelopes typically associated with caustics. This enables more accurate density estimation along overlapping illumination, thus producing more accurate renders. The technique is described in an upcoming Eurographics 2013 paper. See their previous prize winning entry for 2009.

Temporal Visualization of Boundary-based Geo-information Using Radial Projection

This work is concerned with a design study by an interdisciplinary team on visualizing a 10-year record of seasonal and inter-annual changes in frontal position (advance/retreat) of nearly 200 marine terminating glaciers in Greenland. Whilst the spatiotemporal nature of the raw data presents a challenge to develop a compact and intuitive visual design, the focus on coastal boundaries provides an opportunity for dimensional reduction. In this paper, we report the user-centered design process carried out by the team, and present several visual encoding schemes that have met the requirements including compactness, intuitiveness, and ability to depict temporal changes and spatial relations. In particular, we designed a family of radial visualization, where radial lines correspond to different coastal locations, and nested rings represent the evolution of the temporal dimension from inner to outer circles. We developed an algorithm for mapping glacier terminus positions from Cartesian coordinates to angular coordinates. Instead of a naive uniform mapping, the algorithm maintains consistent spatial perception of the visually-sensitive geographical references between their Cartesian and angular coordinates, and distributes other termini positions between primary locations based on coastal distance. This work has provided a useful solution to address the problem of inaccuracy in change evaluation based on pixel-based visualization [BPC10].

Y. Drocourt, R. Borgo, K. Scharrer, T. Murray, S.I. Bevan, M. Chen.
Computer Graphics Forum Intl. Journal, volume 30, number 3, year 2011, pp. 981-990, presented also at EuroVis Conference 2011, May 31-June 3, Bergen, Norway.

Into the Blue: Better Caustics through Photon Relaxation

The photon mapping method is one of the most popular algorithms employed in computer graphics today. However, obtaining good results is dependent on several variables including kernel shape and bandwidth, as well as the properties of the initial photon distribution. While the photon density estimation problem has been the target of extensive research, most algorithms focus on new methods of optimising the kernel to minimise noise and bias. In this paper we break from convention and propose a new approach that directly redistributes the underlying photons. We show that by relaxing the initial distribution into one with a blue noise spectral signature we can dramatically reduce background noise, particularly in areas of uniform illumination. In addition, we propose an efficient heuristic to detect and preserve features and discontinuities. We then go on to demonstrate how reconfiguration also permits the use of very low bandwidth kernels, greatly improving render times whilst reducing bias.

Ben Spencer and Mark W. Jones.
Eurographics 2009, Computer Graphics Forum 28(2) 319-328, 2009. [doi] [BibTeX]