Alejandro Sztrajman

I'm a postdoctoral research associate at the University of Cambridge. 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 Substance 3D. 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

	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 In Review (2024). Keywords: Diffusion Models, 3D Point Clouds. arXiv PDF
	Hypernetworks for Generalizable BRDF Estimation Fazilet Gozbudak, Alejandro Sztrajman, Chenliang Zhou, Fangcheng Zhong, Rafal Mantiuk, Cengiz Öztireli In Review (2024). Keywords: Neural Fields, Hypernetworks, Generalizable Models, Material Appearance. Webpage arXiv PDF
	iHyperTime: Interpretable Time Series Generation with Implicit Neural Representations Elizabeth Fons, Alejandro Sztrajman, Yousef El-Laham, Andrea Coletta, Alexandros Iosifidis, Svitlana Vyetrenko In Review (2024). Keywords: Time-series, Neural Fields, Generative Models, Interpretability, Hypernetworks. OpenReview PDF
	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 NeurIPS (2023). Keywords: Neural Fields, Hypernetworks, Constrained Learning. Webpage arXiv PDF
	Color Calibration Methods for OLED Displays Maliha Ashraf, Alejandro Sztrajman, Dounia Hammou, Rafał Mantiuk Color Imaging (2023). Keywords: Color Correction, Implicit Neural Representations. PDF
	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. OpenReview PDF
	Neural BRDF Representation and Importance Sampling (Wiley Top Cited Paper) Alejandro Sztrajman, Gilles Rainer, Tobias Ritschel, Tim Weyrich Computer Graphics Forum (CGF), 40(6), pp. 332-346, 2021 (Oral Presentation at EGSR 2022). Keywords: Material Appearance, Implicit Neural Representations, Meta-learning, Hypernetworks, Differentiable Rendering, Monte Carlo Sampling. Webpage PDF PDF (lowres) WebGL Demo Code BibTeX
	Fast Blue Noise Generation via Unsupervised Learning Daniele Giunchi, Alejandro Sztrajman, Anthony Steed International Joint Conference on Neural Networks (IJCNN), Padua, Italy, July 2022 (Oral Presentation). Keywords: Blue-Noise, Unsupervised Learning, Dithering, Monte Carlo Integration. Webpage PDF Code BibTeX
	Machine Learning Applications in Appearance Modelling Alejandro Sztrajman University College London, 2022 (PhD Thesis). Reviewers: Profs. Lourdes Agapito and Diego Gutierrez. UCL Repository PDF
	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. Webpage PDF PDF (lowres) BibTeX
	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. Webpage PDF BibTeX
	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. Webpage PDF PDF (lowres) BibTeX Code
	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. Webpage PDF BibTeX
	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. Book Preface Media Coverage

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) Page
	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). Page PDF

Some Old Codes

	Feature Saliency HMM Implementation of the Feature Saliency HMM algorithm, for feature selection on Hidden Markov Models. [Code] Python Hidden Markov Model
	Path tracing A path tracer with support for environment map illumination. [Code] C++ Global Illumination
	2D Lattice-Boltzmann Simulation Interactive simulation of incompressible viscous fluid with Lattice-Boltzmann D2Q9. [Code] [Video] C++ Qt Physics-based Animation

	UTIA BRDF Reader Script to read measured BRDF data from the UTIA BRDF database. [Code] Python BRDF
	WebGL 3D Engine An interactive WebGL 3D engine with phong shading and support for Bezier surfaces. [Video] [Code] [Try it!] Javascript WebGL
	2D FLIP Simulation Fluid Implicit Particle (FLIP) simulation of a 2D incompressible inviscid fluid. [Code] [Video] C++ Qt Physics-based Animation

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