Accordance of Light Scattering from Design and De-Facto Variants of a Daylight Redirecting Component

Noback, Andreas; Grobe, Lars Oliver; Wittkopf, Stephen

doi:10.3390/buildings6030030

Cited by 15 publications

(4 citation statements)

References 21 publications

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“…In Noback et al [2016], a forward ray-tracing algorithm implemented in a photon map extension to Radiance [Schregle et al 2015] was used to generate BSDF data for a complex louver system involving highly reflective surfaces. The study proposed two metrics for characterizing the variation in BSDF data given manufacturing deviations from the design geometry.…”

Section: Generating Bsdfs Using a Geometric Model And Materials Propermentioning

confidence: 99%

Modeling the direct sun component in buildings using matrix algebraic approaches: Methods and validation

Lee

Geisler‐Moroder

Ward³

2018

Solar Energy

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Simulation tools that enable annual energy performance analysis of optically-complex fenestration systems have been widely adopted by the building industry for use in building design, code development, and the development of rating and certification programs for commercially-available shading and daylighting products. The tools rely on a three-phase matrix operation to compute solar heat gains, using as input lowresolution bidirectional scattering distribution function (BSDF) data (10-15° angular resolution; BSDF data define the angle-dependent behavior of light-scattering materials and systems). Measurement standards and product libraries for BSDF data are undergoing development to support solar heat gain calculations. Simulation of other metrics such as discomfort glare, annual solar exposure, and potentially thermal discomfort, however, require algorithms and BSDF input data that more accurately model the spatial distribution of transmitted and reflected irradiance or illuminance from the sun (0.5° resolution).This study describes such algorithms and input data, then validates the tools (i.e., an interpolation tool for measured BSDF data and the five-phase method) through comparisons with ray-tracing simulations and field monitored data from a full-scale testbed. Simulations of daylight-redirecting films, a micro-louvered screen, and venetian blinds using variable resolution, tensor tree BSDF input data derived from interpolated scanning goniophotometer measurements were shown to agree with field monitored data to within 20% for greater than 75% of the measurement period for illuminance-based performance parameters. The threephase method delivered significantly less accurate results. We discuss the ramifications of these findings on industry and provide recommendations to increase end user awareness of the current limitations of existing software tools and BSDF product libraries.

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Section: Generating Bsdfs Using a Geometric Model And Materials Propermentioning

confidence: 99%

Modeling the direct sun component in buildings using matrix algebraic approaches: Methods and validation

Lee

Geisler‐Moroder

Ward³

2018

Solar Energy

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“…Global Accordance (GA) and Local Accordance (LA) are applied to compare the two DSFs of a CFS for one given incident direction [37]. These metrics are based on the pair-wise comparison of values for identical directions.…”

Section: Comparison Of the Results Of The Extended Matrix Formalism Amentioning

confidence: 99%

Computational Combination of the Optical Properties of Fenestration Layers at High Directional Resolution

Grobe

2017

Buildings

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Abstract: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.

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“…In wg2 and wg3, configuration CFS2 retro-reflects sun-light to reduce glare and solar gains. It maintains a view to the outside due to the particular profile of the slats allowing an almost horizontal orientation [44,45]. The system is chosen as an example that allows both geometric and data-driven modelling.…”

Section: Fs1: Static Retro-reflecting Fenestrationmentioning

confidence: 99%

Photon-mapping in Climate-Based Daylight Modelling with High-resolution BSDFs

Grobe

2019

Energy and Buildings

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Visual comfort assessments employing luminance-based metrics rely on efficient CBDM techniques for image synthesis. Data-driven BSDF models allow to isolate internal light paths in optically CFS from CBDM. Bidirectional photon mapping is proposed for the efficient sampling of such models in the calculation of the direct solar component in CBDM. The method allows accurate image synthesis for visual comfort assessments with only two calculation steps, achieving comparable accuracy as the established but complex 5PM. The validity of the approach is confirmed by comparison with backward ray-tracing. Its exemplary application to compare two CFS in terms of glare control demonstrates the importance to achieve reconcilability of conflicting targets such as view and glare control in daylighting.

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Accordance of Light Scattering from Design and De-Facto Variants of a Daylight Redirecting Component

Cited by 15 publications

References 21 publications

Modeling the direct sun component in buildings using matrix algebraic approaches: Methods and validation

Modeling the direct sun component in buildings using matrix algebraic approaches: Methods and validation

Computational Combination of the Optical Properties of Fenestration Layers at High Directional Resolution

Photon-mapping in Climate-Based Daylight Modelling with High-resolution BSDFs

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