A Realistic, Generic Earth/Atmosphere Model - CS348B Final Project

Dick Brouwer

Overview

Rendering scenes, especially outdoors, generally involves using manually created environment maps or other 'hacks' to realistically render skylight. Especially for twilight scenes with very diverse lightning conditions no suitable tools are available (to my knowledge). I want to create a generic model for rendering a realistic sky for a given position on the earth, season, time of day and atmosphere condition (e.g. foggy, polluted etc.). Developing a flexible model would eliminate the use for many of us to re-create the effects of outdoor lighting. If my model turns out to be very computational intensive, it could at least be used to pre-process realistic environment maps to be re-used in renderings.

To accurately render skylights many atmospheric effects have to be taken into account, inluding:

• solar irradiance spectrum and its absorption in the ozone layer,
• wavelength-dependent refraction of direct sunlight in the atmosphere,
• climate-dependent composition and size distribution of aerosols / dust particles,
• height-dependent air, humidity, and aerosol density,
• Rayleigh scattering (air molecules) and Mie scattering (aerosols),
• radiative transfer (multiple scattering), as well as
• the shadow of the Earth.