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    Alejandro Sztrajman

    I'm a postdoctoral research associate in the Rainbow Group at the University of Cambridge, where I work with Profs. Cengiz Öztireli and Rafał Mantiuk. I hold a PhD in Computer Science from University College London (UCL), where I worked at the Digital Reality Lab, under the supervision of Profs. Tim Weyrich and Tobias Ritschel. My research is in the intersection between machine learning and visual computing, combining methods from neural fields, hypernetworks, physically-based rendering and generative models. My PhD project was funded by a Marie Curie Fellowship, granted by the European Commission. During my PhD I also worked as research intern at Microsoft and Adobe. Before joining UCL, I obtained a BSc in Physics from the University of Buenos Aires, and I was a visiting student at the Columbia Computer Graphics Group.


    Contact
    Room SE18
    Computer Laboratory
    William Gates Building
    15 JJ Thomson Avenue
    University of Cambridge, UK

    Publications

    Physically Based Neural Bidirectional Reflectance Distribution Function
    Chenliang Zhou, Alejandro Sztrajman, Gilles Rainer, Fangcheng Zhong, Fazilet Gokbudak, Zhilin Guo, Weihao Xia, Rafal Mantiuk, Cengiz Oztireli.
    In Review, 2024.
    Keywords: Physics-Informed Neural Networks, Neural Fields, Physics-based Rendering.
    iHyperTime: Interpretable Time Series Generation with Implicit Neural Representations
    Elizabeth Fons, Alejandro Sztrajman, Yousef El-Laham, Andrea Coletta, Alexandros Iosifidis, Svitlana Vyetrenko.
    Transactions on Machine Learning Research (TMLR), 2024.
    Keywords: Time-series, Neural Fields, Generative Models, Interpretability, Hypernetworks.
    FrePolad: Frequency-Rectified Point Latent Diffusion for Point Cloud Generation
    Chenliang Zhou, Fangcheng Zhong, Param Hanji, Zhilin Guo, Kyle Thomas Fogarty, Alejandro Sztrajman, Hongyun Gao, Cengiz Oztireli.
    European Conference on Computer Vision (ECCV), 2024.
    Keywords: Diffusion Models, 3D Point Clouds.
    Hypernetworks for Generalizable BRDF Estimation
    Fazilet Gozbudak, Alejandro Sztrajman, Chenliang Zhou, Fangcheng Zhong, Rafal Mantiuk, Cengiz Oztireli.
    European Conference on Computer Vision (ECCV), 2024.
    Keywords: Neural Fields, Hypernetworks, Generalizable Models, Material Appearance.
    Neural Fields with Hard Constraints of Arbitrary Differential Order
    Fangcheng Zhong, Kyle Fogarty, Param Hanji, Tianhao Wu, Alejandro Sztrajman, Andrew Spielberg, Andrea Tagliasacchi, Petra Bosilj, Cengiz Oztireli.
    Conference on Neural Information Processing Systems (NeurIPS), 2023.
    Keywords: Neural Fields, Hypernetworks, Constrained Learning.
    Color Calibration Methods for OLED Displays
    Maliha Ashraf, Alejandro Sztrajman, Dounia Hammou, Rafał Mantiuk.
    Electronic Imaging, 2023.
    Keywords: Color Correction, Implicit Neural Representations.
    HyperTime: Implicit Neural Representations for Time-Series
    Elizabeth Fons, Alejandro Sztrajman, Yousef El-Laham, Alexandros Iosifidis, Svitlana Vyetrenko.
    NeurIPS SyntheticData4ML, 2022.
    Keywords: Time-series, Neural Fields, Signal Processing, Hypernetworks.
    Neural BRDF Representation and Importance Sampling (Wiley Top Cited Paper)
    Alejandro Sztrajman, Gilles Rainer, Tobias Ritschel, Tim Weyrich.
    Computer Graphics Forum (CGF), 2021 (Oral Presentation at EGSR 2022).
    Keywords: Material Appearance, Neural Fields, Meta-learning, Hypernetworks, Differentiable Rendering, Monte Carlo Importance Sampling.
    Fast Blue Noise Generation via Unsupervised Learning
    *Daniele Giunchi, *Alejandro Sztrajman, Anthony Steed.
    International Joint Conference on Neural Networks (IJCNN), 2022 (Oral Presentation).
    Keywords: Blue-Noise, Unsupervised Learning, Dithering, Monte Carlo Integration.
    Machine Learning Applications in Appearance Modelling
    Alejandro Sztrajman.
    University College London, 2022 (PhD Thesis).
    Reviewers: Profs. Lourdes Agapito and Diego Gutierrez.

    Mixing Modalities of 3D Sketching and Speech for Interactive Model Retrieval in Virtual Reality
    Daniele Giunchi, Alejandro Sztrajman, Stuart James, Anthony Steed.
    ACM International Conference on Interactive Media Experiences (IMX), New York, USA, Jun 2021 (Oral Presentation).
    Keywords: Virtual Reality, 3D Sketching, CNNs, Human-in-the-loop.
    High-Dynamic-Range Lighting Estimation from Face Portraits
    Alejandro Sztrajman, Alexandros Neophytou, Tim Weyrich, Eric Sommerlade.
    International Conference on 3D Vision (3DV), Fukoka, Japan, Nov 2020 (Oral Presentation).
    Keywords: HDR Lighting, CNNs, Inverse Rendering, Light Estimation.
    Image-based remapping of spatially-varying material appearance
    Alejandro Sztrajman, Jaroslav Krivanek, Alexander Wilkie, Tim Weyrich.
    Journal of Computer Graphics Techniques (JCGT), 8(4), pp. 1-30, 2019.
    Keywords: Material Appearance, SVBRDF, Non-linear Optimization, Neural Networks.
    Image-based remapping of material appearance
    Alejandro Sztrajman, Jaroslav Krivanek, Alexander Wilkie, Tim Weyrich.
    Eurographics Workshop on Material Appearance Modeling (MAM), Helsinki, Finland, Jun 2017 (Oral Presentation).
    Keywords: Material Appearance, BRDF, Non-linear Optimization.
    An Easy Way to One-Dimensional Elastic Collisions
    Jorge Sztrajman, Alejandro Sztrajman.
    The Physics Teacher (TPT) 55 (3), pp. 164-165.
    Keywords: Physics, Education.
    Elementary Electromagnetism
    Juan G. Roederer.
    Buenos Aires University Press, Buenos Aires (2015).

    I coordinated the editorial team behind the undergraduate textbook by Prof. Juan Roederer. The book was first published in 2015. A second edition was released in 2018, and a digital edition followed in 2020.

    Patents

    Method and System for Generation of Interpretable Time Series with Implicit Neural Representations
    Elizabeth Fons, Svitlana Vyetrenko, Yousef El-Laham, Alejandro Sztrajman, Alexandros Iosifidis
    US Patent App. 18/215, 499 (Pending, 2024)
    Estimating Illumination in an Environment Based on an Image of a Reference Object
    Alexandros Neophytou, Eric Sommerlade, Alejandro Sztrajman, Sunando Sengupta
    US Patent 0116549 A1 (2022).

    Talks

    Relightable 3D Gaussian Splatting
    University of Cambridge, 19 Dec 2023.
    Neural Radiance Fields
    Homerton College, University of Cambridge, 14 Aug 2023 | Cambridge Summer Course.
    Neural Fields for Data Representation and Generation
    Brown University, 17 Oct 2022.
    High-Dynamic-Range Lighting Estimation from Face Portraits
    Virtual, 27 Nov 2020 | International Conference on 3D Vision.
    CNN-based Face Relighting
    Microsoft, Seattle, USA (virtual), 12 Mar 2020.
    Capture and Editing of Material Appearance
    ETH, Zurich, Switzerland. 5 Feb 2018.
    Introduction to Convolutional Neural Networks
    IST, Vienna, Austria. 14 Nov 2017.
    Image-based Remapping of Material Appearance
    Helsinki, Finland, 18 Jun 2017 | Eurographics Workshop on Material Appearance Modelling.

    Teaching

    2023 Advanced Graphics and Image Processing Cambridge
    2023 Introduction to Graphics Cambridge
    2019 Advanced Deep Learning and Reinforcement Learning UCL/DeepMind
    2018 Research Methods and Reading UCL
    2017 Scientific Programming in Python UCL
    2016 Robotics Programming UCL
    2016 Principles of Programming UCL




    Alejandro Sztrajman
    alejandro.sztrajman@cl.cam.ac.uk