Realistic Solar Disc Rendering

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Realistic Solar Disc Rendering
WSCG 2005 Plzen 02 February 2005
Andrei Lintu, Joerg Haber and Marcus Magnor
Max-Planck-Institut für Informatik
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Motivation

• Simulate realistic sunset scenarios

Photo by Edilson de Aguiar, used with permission
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Outline

• Related Work
• Solar Disc Rendering
• Results
• Sunset Science

Photo by Mario Cogo, www.intersoft.it/galaxlux,
used with permission
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Related Work

• Solar Disc
• Ray-tracing one given climate
• Bruton 1996
• Sloup 2003
• Photon mapping
• Gutierrez et al. SCCG 2004
• Atmosphere
• Daylight
• Preetham et al. SIGGRAPH 1999
• Twilight multiple climates
• Haber, Magnor and Seidel, to appear

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Solar Disc Rendering. Method description

• Input parameters
• Temperature profile, climate, number of layers,
  observer height
  
• Precompute radius of curvature
• Trace parabolic rays solar disc shape
• Extinction factor solar disc color

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Atmosphere Model

• Geocentrical layers Li, (i 1, , N)
• Each layer
• Air scattering and extinction coef.
• Aerosol scattering coef.
• Aerosol extinction coef.
• Mean index of refraction
• Indices of refraction
• corresponding to
• and
• Solar Irradiance
• Using N 300-30000 layers

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Ray-tracing

• Precompute for each layer
• Distance traveled
• Decision to take Path 1 or Path 2
• Input temperature profile - index of refraction

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Atmospheric Extinction

• Intensity that reaches observer
• Extinction numerically determined by
• All computations sampled for
• N 8 Wavelengths of the visible spectra

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Results. Sunset scenario

Simulated Sunset Scenario for a Continental
Climate
80 Humidity
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More Sunset Scenarios
Simulated Sunset Scenario for a Maritime Climate
Simulated Sunset Scenario for an Urban Climate
70 Humidity
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Sequences for different climates
Maritime Tropical Climate. Top to bottom 80 and

90 humidity
Continental Average Climate. Top to bottom 50,
80 and
90 humidity
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Mirages. Solar Disc

• Inferior mirages
• mirrored image below object
• Superior mirages
• mirrored image above object
• Solar disc flattens with altitude

Photos by Pekka Parviainen, www.polarimage.fi
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Atmosphere Temperature Profiles

• Starting point U.S. Standard Atmosphere
• Depending on the inversion layers - new
  Atmosphere Profiles are generated
  

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Solar Disc Mirages
Inferior Mirage
Superior Mirage
Mock Mirage
Note Figures are not to scale
Figures by Andrew T. Young, www.mintaka.sdsu.edu/G
F
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The Green Flash
Photograph
Simulated Sequence

• At the top of the solar disc at sunset
• Due to
• Atmospheric dispersion
• Refraction varies
• Atmospheric extinction
• Scattering
• Absorption

Photo by Mario Cogo, www.intersoft.it/galaxlux,
used with permission
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The Red Flash
Simulated Sequence
Photograph

• Due to an inferior or a mock mirage
• Small hue difference
• red - yellow

Photo by Mario Cogo, www.intersoft.it/galaxlux,
used with permission
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Omega sun
Simulated Sequence
Photograph
A Mock Mirage Example
Movie Sequence
Photo by Mario Cogo, www.intersoft.it/galaxlux,
used with permission
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Conclusions

• System for rendering realistic solar disc for
  different given
  
• Climate
• Humidity
• Temperature Profiles
• Spectral Rendering

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