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All Outputs (26)

A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image (2024)
Presentation / Conference Contribution
Westmacott, H., Ivrissimtzis, I., & Weinzierl, T. (2024, January). A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image. Presented at ICIGP 2024: The 7th International Conference on Image and Graphics Processing, Beijing, China

We produce thickness and bone to soft tissue ratio estimations from a single, 2D medical X-ray image. For this, we simulate the scattering of the rays through a model of the object and embed this simulation into an optimiser which iteratively adjusts... Read More about A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image.

Anomaly Detection with Transformers in Face Anti-spoofing (2023)
Presentation / Conference Contribution
Abduh, L., Omar, L., & Ivrissimtzis, I. (2023, May). Anomaly Detection with Transformers in Face Anti-spoofing. Presented at WSGC 2023: 31. International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision 2023, Plzen, Czech Republic

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.

Race Bias Analysis of Bona Fide Errors in Face Anti-spoofing (2023)
Presentation / Conference Contribution
Abduh, L., & Ivrissimtzis, I. (2023, September). Race Bias Analysis of Bona Fide Errors in Face Anti-spoofing. Presented at CAIP 2023: The 20th International Conference on Computer Analysis of Images and Patterns, Limassol, Cyprus

The study of bias in Machine Learning is receiving a lot of attention in recent years, however, few only papers deal explicitly with the problem of race bias in face anti-spoofing. In this paper, we present a systematic study of race bias in face ant... Read More about Race Bias Analysis of Bona Fide Errors in Face Anti-spoofing.

Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language (2023)
Presentation / Conference Contribution
Wang, J., Ivrissimtzis, I., Li, Z., Zhou, Y., & Shi, L. (2023, September). Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language. Presented at ECTEL 2023: Eighteenth European Conference on Technology Enhanced Learning, Aveiro, Portugal

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)
Presentation / Conference Contribution
Wang, J., Ivrissimtzis, I., Li, Z., Zhou, Y., & Shi, L. (2023, August). Developing and Evaluating a Novel Gamified Virtual Learning Environment for ASL. Presented at INTERACT 2023: IFIP Conference on Human-Computer Interaction, York

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)
Presentation / Conference Contribution
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2021, June). Quality perception and discrimination thresholds in quantised triangle meshes. Presented at Sixth International Workshop on Pattern Recognition, Beijing, China

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)
Presentation / Conference Contribution
Abduh, L., & Ivrissimtzis, I. (2019, December). Colour Processing in Adversarial Attacks on Face Liveness Systems. Presented at Computer Graphics and Visual Computing (CGVC), Bangor, UK

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.

A Perceptual Difference Scaling Study on Quantized 3D Models (2018)
Presentation / Conference Contribution
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2018, December). A Perceptual Difference Scaling Study on Quantized 3D Models. Paper presented at ACM Symposium on Applied Perception, Vancouver, Canada

Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks (2018)
Presentation / Conference Contribution
Zhang, X., Wang, Q., & Ivrissimtzis, I. (2018, December). Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks. Presented at EG UK Computer Graphics & Visual Computing, Swansea, UK

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)
Presentation / Conference Contribution
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2017, September). A user study on quantisation thresholds of triangle meshes. Presented at Computer Graphics and Visual Computing (CGVC) 2017., Manchester, England

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)
Presentation / Conference Contribution
Yang, Y., Rushmeier, H., & Ivrissimtzis, I. (2016, June). Order-randomized Laplacian mesh smoothing. Presented at 9th International Conference on Mathematical Methods for Curves and Surfaces, Tønsberg, Norway

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)
Presentation / Conference Contribution
Omar, L., & Ivrissimtzis, I. (2016, November). Designing a facial spoofing database for processed image attacks. Presented at 7th International Conference on Imaging for Crime Detection and Prevention., Madrid, Spain

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)
Presentation / Conference Contribution
Omar, L., & Ivrissimtzis, I. (2023, May). Resilience of Luminance based Liveness Tests under Attacks with Processed Imposter Images. Presented at 24th International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision 2016 (WSCG 2016)., Plzen, Czech Republic

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)
Presentation / Conference Contribution
Omar, L., & Ivrissimtzis, I. (2015, September). Evaluating the Resilience of Face Recognition Systems Against Malicious Attacks. Presented at 7th UK Computer Vision Student Workshop (BMVW), Swansea, UK

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)
Presentation / Conference Contribution
Kaye, D., & Ivrissimtzis, I. (2015, March). Mesh Alignment using Grid based PCA. Presented at 10th International Conference on Computer Graphics Theory and Applications (VISIGRAPP 2015), Berlin, Germany

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)
Presentation / Conference Contribution
Yang, Y., Pintus, R., Rushmeier, H., & Ivrissimtzis, I. (2014, October). A steganalytic algorithm for 3D polygonal meshes. Presented at 2014 IEEE International Conference on Image Processing (ICIP), Paris, France

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)
Presentation / Conference Contribution
Roberts, D., Ivrissimtzis, I., & Holliman, N. (2014, September). An evaluation of reconstruction filters for a path-searching task in 3D. Presented at 2014 Sixth International Workshop on Quality of Multimedia Experience (QoMEX), Singapore, Singapore

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.

Model selection for the Dubuc-Deslauriers family of subdivision schemes (2013)
Presentation / Conference Contribution
Mustafa, G., & Ivrissimtzis, I. (2013, September). Model selection for the Dubuc-Deslauriers family of subdivision schemes. Presented at 14th IMA Conference on Mathematics of Surfaces, Birmingham, England

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.

Implicit surface reconstruction and feature detection with a learning algorithm (2010)
Presentation / Conference Contribution
Kaye, D., & Ivrissimtzis, I. (2010, September). Implicit surface reconstruction and feature detection with a learning algorithm. Presented at Theory and Practice of Computer Graphics, Sheffield, UK

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.