Anomaly Detection with Transformers in Face Anti-spoofing (2023)
Conference Proceeding
Abduh, L., Omar, L., & Ivrissimtzis, I. (2023). Anomaly Detection with Transformers in Face Anti-spoofing. . https://doi.org/10.24132/JWSCG.2023.10

Transformers are emerging as the new gold standard in various computer vision applications, and have already been used in face anti-spoofing demonstrating competitive performance. In this paper, we propose a network with the ViT transformer and ResNe... Read More about Anomaly Detection with Transformers in Face Anti-spoofing.

Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language (2023)
Conference Proceeding
Wang, J., Ivrissimtzis, I., Li, Z., Zhou, Y., & Shi, L. (2023). Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language. In Responsive and Sustainable Educational Futures: 18th European Conference on Technology Enhanced Learning, EC-TEL 2023, Aveiro, Portugal, September 4–8, 2023, Proceedings (459-474). https://doi.org/10.1007/978-3-031-42682-7_31

Sign languages enable effective communication between deaf and hearing people. Despite years of extensive pedagogical research, learning sign language online comes with a number of difficulties that might be frustrating for some students. Indeed, mos... Read More about Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language.

Developing and Evaluating a Novel Gamified Virtual Learning Environment for ASL (2023)
Conference Proceeding
Wang, J., Ivrissimtzis, I., Li, Z., Zhou, Y., & Shi, L. (2023). Developing and Evaluating a Novel Gamified Virtual Learning Environment for ASL. In Human-Computer Interaction – INTERACT 2023: 19th IFIP TC13 International Conference, York, UK, August 28 – September 1, 2023, Proceedings, Part I (459-468). https://doi.org/10.1007/978-3-031-42280-5_29

The use of sign language is a highly effective way of communicating with individuals who experience hearing loss. Despite extensive research, many learners find traditional methods of learning sign language, such as web-based question-answer methods,... Read More about Developing and Evaluating a Novel Gamified Virtual Learning Environment for ASL.

Quality perception and discrimination thresholds in quantised triangle meshes (2021)
Conference Proceeding
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2021). Quality perception and discrimination thresholds in quantised triangle meshes. . https://doi.org/10.1117/12.2604720

At certain stages of the graphics pipeline, and most notably during compression for transmission and storage, triangle meshes may undergo a fixed-point arithmetic quantisation of their vertex coordinates. This paper presents the results of a psychoph... Read More about Quality perception and discrimination thresholds in quantised triangle meshes.

Colour Processing in Adversarial Attacks on Face Liveness Systems (2019)
Conference Proceeding
Abduh, L., & Ivrissimtzis, I. (2019). Colour Processing in Adversarial Attacks on Face Liveness Systems. In F. P. Vidal, G. K. . L. Tam, & J. C. Roberts (Eds.), Proceedings of Computer Graphics and Visual Computing 2019 (CGVC) (149-152). https://doi.org/10.2312/cgvc.20191272

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... Read More about Colour Processing in Adversarial Attacks on Face Liveness Systems.

Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks (2018)
Conference Proceeding
Zhang, X., Wang, Q., & Ivrissimtzis, I. (2018). Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks. In G. Tam, & F. Vidal (Eds.), Computer Graphics & Visual Computing (CGVC) 2018 : Eurographics UK Chapter proceedings (117-120). https://doi.org/10.2312/cgvc.20182019

In this paper we propose and analyse a method for watermarking 3D printed objects, concentrating on the watermark retrieval problem. The method embeds the watermark in a planar region of the 3D printed object in the form of small semi-spherical or cu... Read More about Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks.

A user study on quantisation thresholds of triangle meshes (2017)
Conference Proceeding
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2017). A user study on quantisation thresholds of triangle meshes. In T. R. Wan, & F. Vidal (Eds.), Computer Graphics & Visual Computing (CGVC) 2017. Eurographics UK Chapter Proceedings, anchester Metropolitan University, United Kingdom, 14 – 15 September 2017. https://doi.org/10.2312/cgvc.20171283

We present the results of a user study on estimating a quantisation threshold above which the quantised triangle mesh is perceived as indistinguishable from its unquantised original. The design of the experiment and the analysis of the results focus... Read More about A user study on quantisation thresholds of triangle meshes.

Order-randomized Laplacian mesh smoothing (2017)
Conference Proceeding
Yang, Y., Rushmeier, H., & Ivrissimtzis, I. (2017). Order-randomized Laplacian mesh smoothing. In M. S. Floater, T. Lyche, M. Mazure, K. Mørken, & L. L. Schumaker (Eds.), Mathematical methods for curves and surfaces : 9th International Conference, MMCS 2016, Tønsberg, Norway, June 23 - June 28, 2016. Revised selected papers (312-323). https://doi.org/10.1007/978-3-319-67885-6_17

In this paper we compare three variants of the graph Laplacian smoothing. The first is the standard synchronous implementation, corresponding to multiplication by the graph Laplacian matrix. The second is a voter process inspired asynchronous impleme... Read More about Order-randomized Laplacian mesh smoothing.

Designing a facial spoofing database for processed image attacks (2016)
Conference Proceeding
Omar, L., & Ivrissimtzis, I. (2016). Designing a facial spoofing database for processed image attacks. In 7th International Conference on Imaging for Crime Detection and Prevention (ICDP 2016) : Madrid, Spain, 23-25 November 2016 ; proceedings. https://doi.org/10.1049/ic.2016.0073

Face recognition systems are used for user authentication in everyday applications such as logging into a laptop or smartphone without need to memorize a password. However, they are still vulnerable to spoofing attacks, as for example when an imposte... Read More about Designing a facial spoofing database for processed image attacks.

Resilience of Luminance based Liveness Tests under Attacks with Processed Imposter Images (2016)
Conference Proceeding
Omar, L., & Ivrissimtzis, I. (2016). Resilience of Luminance based Liveness Tests under Attacks with Processed Imposter Images. In V. Skala (Ed.),

Liveness tests are techniques employed by face recognition authentication systems, aiming at verifying that a live face rather than a photo is standing in front of the system camera. In this paper, we study the resilience of a standard liveness test... Read More about Resilience of Luminance based Liveness Tests under Attacks with Processed Imposter Images.

Evaluating the Resilience of Face Recognition Systems Against Malicious Attacks (2015)
Conference Proceeding
Omar, L., & Ivrissimtzis, I. (2015). Evaluating the Resilience of Face Recognition Systems Against Malicious Attacks. In X. Xie, M. W. Jones, & G. K. L. Tam (Eds.), Proceedings of the 7th UK Computer Vision Student Workshop (BMVW) (5.1-5.9). https://doi.org/10.5244/c.29.bmvw.5

This paper presents an experiment designed to test the resilience of several user verification systems based on face recognition technology against simple identity spoofing methods, such as trying to gain access to the system by using mobile camera s... Read More about Evaluating the Resilience of Face Recognition Systems Against Malicious Attacks.

Mesh Alignment using Grid based PCA (2015)
Conference Proceeding
Kaye, D., & Ivrissimtzis, I. (2015). Mesh Alignment using Grid based PCA. In J. Braz, J. Pettré, & P. Richard (Eds.), Proceedings of the 10th International Conference on Computer Graphics Theory and Applications (VISIGRAPP 2015) : Berlin, Germany, 11-14 March 2015 (174-181). https://doi.org/10.5220/0005313801740181

We present an algorithm for mesh alignment by performing Principal Components Analysis (PCA) on a set of nodes of a regular 3D grid. The use of a 3D lattice external to both inputs increases the robustness of PCA, particularly when dealing with meshe... Read More about Mesh Alignment using Grid based PCA.

A steganalytic algorithm for 3D polygonal meshes (2014)
Conference Proceeding
Yang, Y., Pintus, R., Rushmeier, H., & Ivrissimtzis, I. (2014). A steganalytic algorithm for 3D polygonal meshes. In ICIP 2014 : 2014 IEEE International Conference on Image Processing (ICIP) (4782-4786). https://doi.org/10.1109/icip.2014.7025969

We propose a steganalytic algorithm for watermarks embedded by Cho et al.'s mean-based algorithm [1]. The main observation is that while in a clean model the means of Cho et al.'s normalized histogram bins are expected to follow a Gaussian distributi... Read More about A steganalytic algorithm for 3D polygonal meshes.

An evaluation of reconstruction filters for a path-searching task in 3D (2014)
Conference Proceeding
Roberts, D., Ivrissimtzis, I., & Holliman, N. (2014). An evaluation of reconstruction filters for a path-searching task in 3D. In 2014 Sixth International Workshop on Quality of Multimedia Experience (QoMEX 2014) : Singapore, 18-20 September 2014 (165-170). https://doi.org/10.1109/qomex.2014.6982314

The choice of reconstruction filter used to interpolate between sample points when generating images from volumetric data sets can have an impact on image quality. There are a range of reconstruction filters as well as methods to determine the qualit... Read More about An evaluation of reconstruction filters for a path-searching task in 3D.

A Geometric Approach for the Computation of Principal Directions in Point Sets (2014)
Conference Proceeding
Ivrissimtzis, I. (2014). A Geometric Approach for the Computation of Principal Directions in Point Sets. In R. Borgo, & W. Tang (Eds.), Computer Graphics & Visual Computing (CGVC) 2014 : University of Leeds, Leeds, United Kingdom 10 – 11 September 2014 ; proceedings. https://doi.org/10.2312/cgvc.20141210

Model selection for the Dubuc-Deslauriers family of subdivision schemes (2013)
Conference Proceeding
Mustafa, G., & Ivrissimtzis, I. (2013). Model selection for the Dubuc-Deslauriers family of subdivision schemes. In R. J. Cripps, G. Mullineux, & M. A. Sabin (Eds.), Mathematics of surfaces - XIV. The proceedings of a conference on the Mathematics of Surfaces, organised by the Institute of Mathematics and its Applications held at the University of Birmingham in September 2013 (155-162)

We propose two methods for model selection for the DubucDeslauriers family of subdivision schemes. In particular, we study model selection under the statistical method of cross-validation and the geometric method of minimizing the absolute discrete t... Read More about Model selection for the Dubuc-Deslauriers family of subdivision schemes.

Effects of Noise on Quantized Triangle Meshes (2010)
Conference Proceeding
Ivrissimtzis, I. (2010). Effects of Noise on Quantized Triangle Meshes. In M. Dahlen, M. Floater, T. Lyche, J. Merrien, K. Morken, & L. Schumaker (Eds.), Mathematical methods for curves and surfaces : 7th International Conference, MMCS 2008, 26 June - 1 July, 2008, Tønsberg, Norway ; revised selected papers (274-284). https://doi.org/10.1007/978-3-642-11620-9_18

In this paper we measure the effects of noise on the performance of a standard entropy compression algorithm for quantized triangle meshes. In a first experiment, we show that a small amount of added noise may lead to slightly smaller filesizes. The... Read More about Effects of Noise on Quantized Triangle Meshes.

Implicit surface reconstruction and feature detection with a learning algorithm (2010)
Conference Proceeding
Kaye, D., & Ivrissimtzis, I. (2010). Implicit surface reconstruction and feature detection with a learning algorithm. In J. Collomosse, & I. Grimstead (Eds.),

We propose a new algorithm for implicit surface reconstruction and feature detection. The algorithm is based on a self organising map with the connectivity of a regular 3D grid that can be trained into an implicit representation of surface data. The... Read More about Implicit surface reconstruction and feature detection with a learning algorithm.

Bootstrap test error estimations of polynomial fittings in surface reconstruction. (2009)
Conference Proceeding
Ramli, A., & Ivrissimtzis, I. (2009). Bootstrap test error estimations of polynomial fittings in surface reconstruction. In M. Magnor, B. Rosenhahn, & H. Theisel (Eds.), Proceedings of the Vision, Modeling, and Visualization Workshop 2009: November 16 - 18, 2009, Braunschweig, Germany (101-109)

Distance Based Feature Detection on 3D Point Sets. (2009)
Conference Proceeding
Ahmad, R., & Ivrissimtzis, I. (2009). Distance Based Feature Detection on 3D Point Sets. In W. Tang, & J. Collomosse (Eds.), Theory and practice of computer graphics 2009: Eurographics UK Chapter proceedings ; Cardiff University, United Kingdom, 17th to 19th June 2009; [papers presented at the 6th Theory and Practice of Computer Graphics Conference (TP.CG.09)] (53-56)