Computer Graphics & Visual Computing (CGVC) 2019
Permanent URI for this collection
Browse
Browsing Computer Graphics & Visual Computing (CGVC) 2019 by Subject "Computing methodologies"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Colour Processing in Adversarial Attacks on Face Liveness Systems(The Eurographics Association, 2019) Abduh, Latifah; Ivrissimtzis, Ioannis; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.In the context of face recognition systems, liveness test is a binary classification task aiming at distinguishing between input images that come from real people's faces and input images that come from photos or videos of those faces, and presented to the system's camera by an attacker. In this paper, we train the state-of-the-art, general purpose deep neural network ResNet for liveness testing, and measure the effect on its performance of adversarial attacks based on the manipulation of the saturation component of the imposter images. Our findings suggest that higher saturation values in the imposter images lead to a decrease in the network's performance. Next, we study the relationship between the proposed adversarial attacks and corresponding direct presentation attacks. Initial results on a small dataset of processed images which are then printed on paper or displayed on an LCD or a mobile phone screen, show that higher saturation values lead to higher values in the network's loss function, indicating that these colour manipulation techniques can indeed be converted into enhanced presentation attacks.Item Controlling 3D Visualisations with Multiple Degrees of Freedom(The Eurographics Association, 2019) Sandoval, Mario; Morris, Tim; Turner, Martin; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.In this paper, the two major components of a new multi-layer framework ideal for two-handed interaction in desktop virtual environments called Library for Interactive Settings of User-Mode (LISU) are explained. In addition, we evaluate LISU performance with a group of participants and we report some of our initial results by giving an analysis of user experiences, and interaction speed.Item Evaluating Models for Virtual Forestry Generation and Tree Placement in Games(The Eurographics Association, 2019) Williams, Benjamin; Ritsos, Panagiotis; Headleand, Christopher; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.A handful of approaches have been previously proposed to generate procedurally virtual forestry for virtual worlds and computer games, including plant growth models and point distribution methods. However, there has been no evaluation to date which assesses how effective these algorithms are at modelling real-world phenomena. In this paper we tackle this issue by evaluating three algorithms used in the generation of virtual forests - a randomly uniform point distribution method (control), a plant competition model, and an iterative random point distribution technique. Our results show that a plant competition model generated more believable content when viewed from an aerial perspective. We also found that a randomly uniform point distribution method produced forest visualisations which were rated highest in playability and photorealism, when viewed from a first-person perspective. Our results indicate that when it comes to believability, the relationship between viewing perspective and procedural generation algorithm is more important than previously thought.Item Fast and Efficient Nearest Neighbor Search for Particle Simulations(The Eurographics Association, 2019) Gross, Julian; Köster, Marcel; KrĂĽger, Antonio; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.One of the fundamental algorithms in particle simulations is the identification and iteration over nearest neighbors of every particle. Well-known examples are SPH or PBD simulations that compute forces and particle-position updates in every simulation step. In order to find nearest neighbors for all particles, hash-based, grid-based or tree-based approaches have been developed in the past. The two most prominent and fastest algorithms use virtual and explicitly allocated uniform grids to achieve high performance on Graphics Processing Units (GPUs). However, they have disadvantages with numerous particle simulation domains, either in terms of run time or memory consumption. We present a novel algorithm that can be applied to large simulation domains that significantly reduces memory consumption using a shared-memory based neighbor search. Furthermore, we achieve high-performance on our evaluation scenarios that often outperforms existing state-of-the-art methods.Item Hash-based Hierarchical Caching for Interactive Previews in Global Illumination Rendering(The Eurographics Association, 2019) Roth, Thorsten; Weier, Martin; Bauszat, Pablo; Hinkenjann, AndrĂ©; Li, Yongmin; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Modern Monte-Carlo-based rendering systems still suffer from the computational complexity involved in the generation of noise-free images, making it challenging to synthesize interactive previews. We present a framework suited for rendering such previews of static scenes using a caching technique that builds upon a linkless octree. Our approach allows for memory-efficient storage and constant-time lookup to cache diffuse illumination at multiple hitpoints along the traced paths. Non-diffuse surfaces are dealt with in a hybrid way in order to reconstruct view-dependent illumination while maintaining interactive frame rates. By evaluating the visual fidelity against ground truth sequences and by benchmarking, we show that our approach compares well to low-noise path traced results, but with a greatly reduced computational complexity allowing for interactive frame rates. This way, our caching technique provides a useful tool for global illumination previews and multi-view rendering.Item Optimising Underwater Environments for Mobile VR(The Eurographics Association, 2019) Cenydd, Llyr ap; Headleand, Christopher; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Mobile Virtual Reality (VR) has advanced considerably in the last few years, driven by advances in smartphone technology. There are now a number of commercial offerings available, from smartphone powered headsets to standalone units with full positional tracking. Similarly best practices in VR have matured quickly, facilitating comfortable and immersive VR experiences. There remains however many optimisation challenges when working with these devices, as while the need to render at high frame rates is universal, the hardware is limited by both computational power and battery capacity. There is also often a requirement that apps run smoothly across a wide variety of headsets. In this paper, we describe lessons learned in rendering and optimising underwater environments for mobile VR, based on our experience developing the popular aquatic safari application 'Ocean Rift'. We start by analyzing essential best practices for mobile app development, before describing low-cost techniques for creating immersive underwater environments. While some techniques discussed are universal to modern mobile VR development, we also consider issues that are unique to underwater applications.Item Projectional Radiography Simulator: an Interactive Teaching Tool(The Eurographics Association, 2019) Sujar, Aaron; Kelly, Graham; GarcĂa, Marcos; Vidal, Franck; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Radiographers need to know a broad range of knowledge about X-ray radiography, which can be specific to each part of the body. Due to the harmfulness of the ionising radiation used, teaching and training using real patients is not ethical. Students have limited access to real X-ray rooms and anatomic phantoms during their studies. Books, and now web apps, containing a set of static pictures are then often used to illustrate clinical cases. In this study, we have built an Interactive X-ray Projectional Simulator using a deformation algorithm with a real-time X-ray image simulator. Users can load various anatomic models and the tool enables virtual model positioning in order to set a specific position and see the corresponding X-ray image. It allows teachers to simulate any particular X-ray projection in a lecturing environment without using real patients and avoiding any kind of radiation risk. This tool also allows the students to reproduce the important parameters of a real X-ray machine in a safe environment. We have performed a face and content validation in which our tool proves to be realistic (72% of the participants agreed that the simulations are visually realistic), useful (67%) and suitable (78%) for teaching X-ray radiography.Item Recognising Human-Object Interactions Using Attention-based LSTMs(The Eurographics Association, 2019) Almushyti, Muna; Li, Frederick W. B.; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Recognising Human-object interactions (HOIs) in videos is a challenge task especially when a human can interact with multiple objects. This paper attempts to solve the problem of HOIs by proposing a hierarchical framework that analyzes human-object interactions from a video sequence. The framework consists of LSTMs that firstly capture both human motion and temporal object information independently, followed by fusing these information through a bilinear layer to aggregate human-object features, which are then fed to a global deep LSTM to learn high-level information of HOIs. The proposed approach applies an attention mechanism to LSTMs in order to focus on important parts of human and object temporal information.Item Robust and Flexible Puzzle Solving with Corner-based Cycle Consistent Correspondences(The Eurographics Association, 2019) Wang, T.; Vladimirov, K.; Goh, S.; Lai, Y.-K.; Xie, X.; Tam, G. K. L.; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Solving jigsaw puzzles is a classic problem in computer vision with various applications. Over the past decades, many useful approaches have been introduced. Most existing works use edge-wise similarity measures for assembling puzzles with square pieces of the same size, and recent work innovates to use the loop constraint to improve efficiency and accuracy. We observe that most existing techniques cannot be easily extended to puzzles with rectangular pieces of arbitrary sizes, and no existing loop constraints can be used to model such challenging scenarios. In this paper, we propose a new corner-wise matching approach, modelled using the MatchLift framework to solve square puzzles with cycle consistency. We further show one exciting example illustrating how puzzles with rectangular pieces of arbitrary sizes would be solved by our technique.