Architecture / Mimarlık

Permanent URI for this collectionhttps://hdl.handle.net/11147/24

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Subject: search.filters.subject.Bidirectional Scatter Distribution Function

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 12
    Citation - Scopus: 15
    Characterization and Data-Driven Modeling of a Retro-Reflective Coating in Radiance
    (Elsevier Ltd., 2018) Grobe, Lars Oliver
    Retro-reflective coatings applied to blinds of reduced geometric complexity promise to provide view to the outside while effectively controlling solar gains and glare. To characterize the reflection characteristics of such coatings over the entire solar spectrum, a novel extension to a scanning gonio-photometer is developed. The extended instrument is tested and applied to measure a coating's Bidirectional Reflection Distribution Function including the region of the retro-reflected peak. The measured datasets are compiled into a data-driven reflection model for the daylight simulation software RADIANCE. This model is applied to illustrate the coating's effect in a comparison to purely diffuse and specular surface finishes on geometrically identical, flat blinds. Daylight supply, the probability of glare, and solar gains are assessed for an exemplary, South-oriented office under sunny sky conditions. The results indicate the potential of the coating to effectively shade direct sunlight even if applied on blinds with minimalistic geometries. The modeling technique is shown to be a general means to replicate the irregular optical properties of the coating, which cannot be represented by the standard models in daylight simulation software.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 8
    Computational Combination of the Optical Properties of Fenestration Layers at High Directional Resolution
    (MDPI Multidisciplinary Digital Publishing Institute, 2017) Grobe, Lars Oliver
    Complex fenestration systems typically comprise co-planar, clear and scattering layers. As there are many ways to combine layers in fenestration systems, a common approach in building simulation is to store optical properties separate for each layer. System properties are then computed employing a fast matrix formalism, often based on a directional basis devised by JHKlems comprising 145 incident and 145 outgoing directions. While this low directional resolution is found sufficient to predict illuminance and solar gains, it is too coarse to replicate the effects of directionality in the generation of imagery. For increased accuracy, a modification of the matrix formalism is proposed. The tensor-tree format of RADIANCE, employing an algorithm subdividing the hemisphere at variable resolutions, replaces the directional basis. The utilization of the tensor-tree with interfaces to simulation software allows sharing and re-use of data. The light scattering properties of two exemplary fenestration systems as computed employing the matrix formalism at variable resolution show good accordance with the results of ray-tracing. Computation times are reduced to 0.4% to 2.5% compared to ray-tracing through co-planar layers. Imagery computed employing the method illustrates the effect of directional resolution. The method is supposed to foster research in the field of daylighting, as well as applications in planning and design.
  • Article
    Citation - Scopus: 8
    High-Resolution Data-Driven Models of Daylight Redirection Components
    (TU Delft Open, 2017) Grobe, Lars Oliver; Wittkopf, Stephen; Kazanasmaz, Zehra Tuğçe
    Daylight Redirecting Components (DRCs) guide daylight to zones with insufficient daylight exposure. They reduce energy demand for lighting, heating and cooling, and improve visual and thermal comfort. The data-driven model in Radiance is a means to model DRCs in daylight simulation. Rather than internal optical mechanisms, their resulting Bidirectional Scattering Distribution Function (BSDF) is replicated. We present models of two DRCs that are generated from measurements. The impact of the following three necessary steps in the generation of data-driven models from measured BSDF shall be evaluated: 1) interpolation between measurements at sparse sets of incident directions; 2) extrapolation for directions that cannot be measured; 3) application of a directional basis of given directional resolution. It is shown that data-driven models can provide a realistic representation of both DRCs. The sensitivity to effects from interpolation differs for the two DRCs due to the varying complexity of their BSDFs. Due to the irregularity of the measured BSDFs, extrapolation is not reliable and fails for both tested DRCs. Different measurement and modeling protocols should be applied to different class systems, rather than aiming at a common low-resolution discretization.
  • Conference Object
    Comparison of Measured and Computed Bsdf of a Daylight Redirecting Component
    (EPFL Scientific Publications, 2015) Grobe, Lars Oliver; Noback, A.; Wittkopf, Stephen; Kazanasmaz, Zehra Tuğçe
    The Bidirectional Scatter Distribution Function (BSDF) of a selected Daylight Redirecting Component (DRC) is computed by a virtual goniophotometer using the enhanced photon map extension in Radiance, and compared to measured BSDF data. The DRC comprises a stack of tilted aluminum louvers with configurable inclination angle. The profile of the louvers is designed to control transmission depending on sun altitude, and to redirect light up towards the ceiling. The measured BSDF of the DRC is obtained from a scanning goniophotometer. For a sparse set of three source directions, the distribution is recorded at ≃ 250,000 receiver directions. The asymmetric angular resolution allows detailed observation of characteristic features in the distribution, which are assumed to persist over a range of source directions. For each pair of source and receiver directions in the measurement, the computed BSDF is generated from a model of the DRC, replicating the measurement with a virtual goniophotometer. The simulation relies only on the enhanced photon map extension for Radiance. The BSDF from measurement and simulation are compared qualitatively and quantitatively to discuss the degree of accordance. The presence of characteristic features and their topology is evaluated by comparing polar surface plots of the distributions and profiles of the scatter plane. The direct-hemispherical transmission is compared for each measurement and simulation. The RMSE of each computed distribution against the corresponding measurements is calculated to quantify the directionally resolved deviation. A high degree of qualitative accordance between the computed and the measured BSDF is achieved. Prominent features in the BSDF are represented by the model. A deviation of −6% to +15% is observed in a quantitative comparison of direct-hemispherical transmission by integration of computed and measured BSDF. The RMSE indicates higher deviations for lower source altitudes, where a direct transmission peak in the distribution is underestimated by the model. The method is proposed as a means to validate the capability of the enhanced photon map to predict transmission through DRC.