Research - Lighting Optimization
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A Generative Approach to Light Placement for Street Lighting
I. Evangelou, N. Vitsas, G. Papaioannou, A. Gkaravelis, Proc. Eurographics 2024 (short paper track), 2024.
Abstract. The design of plausible and effective street lighting configurations for arbitrary urban sites should attain predetermined illuminance levels and adhere to specific layout intentions and functional requirements. This task can be time consuming, even for automated solutions, since there exists an one-to-many mapping between illumination goals and lighting options. In this work, we propose a generative approach for this task, based on an adversarial optimisation scheme. Our proposed method effectively overcomes these task-specific limitations by providing a range of viable solutions that adhere to the input constraints and can be generated within an interactive design life cycle.
Links: Author-prepared version of the paper Eurographics fast-forward video
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Opening Design using Bayesian Optimization
N. Vitsas, I. Evangelou, G. Papaioannou, A. Gkaravelis, Proc. Comp. Graphics International, Virtual Reality and Intelligent Hardware, 5(6), pp. 550-564, https://doi.org/10.1016/j.vrih.2023.06.001, 2023.
Abstract. Opening design is a major consideration in architectural buildings during early structural layout specification. Decisions regarding the geometric characteristics of windows, skylights, hatches, etc., significantly affect the overall energy efficiency, airflow, and appearance of a building both internally and externally. In this work, we employ a goal-based, illumination-driven approach to opening design using a Bayesian optimization approach based on Gaussian processes. A method that enables designers to conveniently set lighting intentions in conjunction with the qualitative and quantitative characteristics of the desired openings is proposed. The parameters are optimized within a cost-minimization framework to calculate geometrically feasible, architecturally admissible, and aesthetically pleasing openings of any desired shape while taking into account the designer's lighting constraints.
Links: Open access paper
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Illumination-driven Light Probe Placement
K. Vardis, A. A. Vasilakis, G. Papaioannou, poster, proc. Eurographics 2021.
Abstract. We introduce a simplification method for light probe configurations that preserves the indirect illumination distribution in scenes with diverse lighting conditions. An iterative graph simplification algorithm discards the probes that, according to a set of evaluation points, have the least impact on the global light field. Our approach is simple, generic and aims at improving the repetitive and often non-intuitive and tedious task of placing light probes on complex virtual environments.
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Illumination-Guided Furniture Layout Optimization
N. Vitsas, G. Papaioannou , A. Gkaravelis, A. A. Vasilakis, Computer Graphics Forum (proc. Eurographics 2020), 39(2), 2020.
Abstract. Lighting plays a very important role in interior design. However, in the specific problem of furniture layout recommendation, illumination has been either neglected or addressed with empirical or very simplified solutions. The effectiveness of a particular layout in its expected task performance can be greatly affected by daylighting and artificial illumination in a non-trivial manner. In this paper, we introduce a robust method for furniture layout optimization guided by illumination constraints. The method takes into account all dominant light sources, such as sun light, skylighting and fixtures, while also being able to handle movable light emitters. For this task, the method introduces multiple generic illumination constraints and physically-based light transport estimators, operating alongside typical geometric design guidelines, in a unified manner. We demonstrate how to produce furniture arrangements that comply with important safety, comfort and efficiency illumination criteria, such as glare suppression, under complex light-environment interactions, which are very hard to handle using empirical or simplified models.
Links: the paper
Media: teaser (EG fast forward) video Eurographics 2020 presentation
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Light Optimization for Detail Highlighting
A. Gkaravelis, G. Papaioannou, Computer Graphics Forum (proc. Pacific Graphics 2018), 37(7), pp. 37-44, October, 2018.
Abstract. In this paper we propose an effective technique for the automatic arrangement of spot lights and other luminaires on or near user-provided arbitrary mounting surfaces in order to highlight the geometric details of complex objects. Since potential applications include the lighting design for exhibitions and similar installations, the method takes into account obstructing geometry and potential occlusion from visitors and other non-permanent blocking geometry. Our technique generates the most appropriate position and orientation for light sources based on a local contrast maximization near salient geometric features and a clustering mechanism, producing consistent and view-independent results, with minimal user intervention. We validate our method with realistic test cases including multiple and disjoint exhibits as well as high occlusion scenarios.
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Detail Highlighting using a Shadow Edge Histogram
A. Gkaravelis, G. Papaioannou, proc. Eurograhpics (short paper), 2017.
Abstract. In this paper we propose a simple and effective technique for setting up a configuration of directional light sources to accentuate the prominent geometric features of complex objects by increasing the local shadow contrast near them. Practical applications of such a task are encountered among others in professional photography, and cinematography. The method itself, which is based on a voting mechanism, quickly produces consistent and view-independent results, with minimal user intervention.
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Inverse Lighting Design using a Coverage Optimization Strategy
A. Gkaravelis, G. Papaioannou, the Visual Computer (proc. CGI 2016), DOI 10.1007/s00371-016-1237-9, 2016.
Abstract. Lighting design is an essential process in computer cinematography, games, architectural design and various other applications for correctly illuminating or highlighting parts of a scene and enhancing storytelling. When targeting specific illumination goals and constraints, this process can be tedious and counterintuitive, even for experienced users and thus automatic, goal-driven methods have emerged for the estimation of a lighting configuration to match the desired result. We present a general automatic approach to such an inverse lighting design problem, where the number of light sources along with their position and emittance are computed given a set of user-specified lighting goals. To this end, we employ a special hierarchical light clustering that operates in the lighting goal coverage domain and overcomes limitations of previous approaches in environments with high occlusion or structural complexity. Our approach is independent of the underlying light transport model and can quickly converge to usable solutions. We validate our results and provide comparative evaluation with the current state of the art.
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A Generic Physically-based Approach to the Opening Design Problem
K. Kalampokis, G. Papaioannou, A. Gkaravelis, Proc. Eurographics 2016 (short paper), 2016.
Abstract. Today architectural design harnesses photorealistic rendering to accurately assess energy transport for the design of energyefficient buildings. In this context, we present an automatic physically-based solution to the opening design problem, i.e. the goal-driven process of defining openings on the input geometry given a set of lighting constraints, to better exploit natural daylight. Based on a hierarchical approach that combines a linear optimization strategy and a genetic algorithm, our method computes the optimal number, position, size and shape of openings, using a path tracing-based estimator to precisely model the light transport for arbitrary materials and geometry. The method quickly converges to an opening configuration that optimally approximates the desired illumination, with no special geometry editing requirements and the ability to trade quality for performance for interactive applications. We validate our results against ground truth experiments for various scenes and time-of-day intervals.
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Inverse Light Design for High-Occlusion Environments
A. Gkaravelis, G. Papaioannou, K. Kalampokis, proc. GRAPP 2015.
Abstract. Lighting design is a demanding but very important task in computer cinematography, games and architectural design. Computer-assisted lighting design aims at providing the designers with tools to describe the desired outcome and derive a suitable lighting configuration to match their goal. In this paper, we present an automatic approach to the inverse light source emittance and positioning problem, based on a layered linear / non-linear optimization strategy and the introduction of a special light source indexing according to the compatibility of each individual luminary position with the desired illumination. Our approach is independent of a particular light transport model and can quickly converge to an appropriate and plausible light configuration that approximates the desired illumination and can handle environments with high occlusion.
