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Outline

Title
Abstract
FAQs
Introduction
Previous Work
Conclusion
References
All Topics
Physics
Optics

Fast Sky Rendering for Daylight & Twilight

Profile image of Abdurrahman ÖzlemAbdurrahman Özlem

2021

https://doi.org/10.13140/RG.2.2.12548.13444
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35 pages

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Abstract

Besides the simulation of daylight luminous intensity distribution for interior architecture, spectral rendering of the sky hemisphere has been a rather important task for the video game developers. A veridical panorama under vigorous conditions in real-time requires a credible sky model as well as a prompt algorithm. The main purpose of this work is confined to the generation of an interactive WEB application which can run on any general purpose device lacking dedicated graphics processing but still can achieve sub-second response time. A convincing clear/turbid sky reproduction for both daylight and twilight was possible thanks to the employment of a single-pass semi-analytical model without the necessity of any precomputing or recursive numerical integration effort. The highly parameterized structure enables to experiment many meteorological variations such as turbidity, altitude or ozone layer thickness. The shadow of the Earth has been empirically included into the algorithm in order to construct the Venus Belt. Some rendered images are compared against real photographs to evaluate the soundness of the proposed framework. The imitation of the Martian sky appearance has further been demonstrated in order to reflect the flexibility of the model to diverse atmospheric compositions.

FAQs

sparkles

AI

What explains the differences in twilight color perception during sunset and sunrise?add

The paper reveals that atmospheric layers receive direct sunlight differently, affecting twilight colors. Zenith brightness diminishes more rapidly during twilight, resulting in distinct color arrangements for ascendant and descendant solar paths.

How does turbidity affect the perceived brightness of the sky?add

The study indicates that increased turbidity decreases brightness perceived at angles close to the horizon. For instance, the extreme values of turbidity observed were T > 50 for dense fog conditions.

What methodological improvements does the semi-analytical model offer for sky rendering?add

The proposed semi-analytical model allows for rendering in under one second on standard hardware without pre-computation. This efficiency is achieved by simplifying complex atmospheric physics while maintaining reasonable accuracy.

When did the understanding of sky luminance evolve significantly in atmospheric science?add

Key advancements began around 1987 with multi-scattering models, culminating in the 2012 Hosek-Wilkie model, which refined previous methods to enhance realism under low solar elevations.

What role does ozone concentration play in sky color during twilight?add

Ozone concentration profoundly influences twilight color composition; higher ozone levels lead to a bluer sky as solar elevation decreases. This effect was quantified, revealing a consistent change in atmospheric hue.

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Related topics

  • Observational Astronomy
  • Real-time rendering
  • Sky Brightness
  • Daylight modelling
  • Multiple Scattering
  • Illumination Engineering
  • Daylight Simulation
  • Atmospheric Refraction
  • Rayleigh Scattering
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