Sn

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Rendering Parametrizable Planetary Atmospheres
with Multiple Scattering in Real-Time
Oskar Elek Charles University Prague
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Motivation

• Why atmosphere?

Oskar Elek
CESCG09
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Motivation

• Why real-time?

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CESCG09
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Outline

• Introduction
• Related work
• Model and its precomputation
• Rendering
• Results
• Conclusion
• Interactive demonstration

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CESCG09
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Outline

• Introduction
• Related work
• Model and its precomputation
• Rendering
• Results
• Conclusion
• Interactive demonstration

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CESCG09
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Introduction

• Participating media

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CESCG09
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Introduction

• Participating media
• Light scattering
• Rayleigh / Mie
• Multiple scattering

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CESCG09
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Introduction

• Participating media
• Light scattering
• Rayleigh / Mie
• Multiple scattering
• Parametrizability

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CESCG09
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Outline

• Introduction
• Related work
• Model and its precomputation
• Rendering
• Results
• Conclusion
• Interactive demonstration

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CESCG09
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Related work

• Scattering physics
• Rayleigh (1871)
• Mie (1908)
• Non-realtime methods
• Nishita et al. (1993, 1996)
• Haber et al. (2005)
• Real-time methods
• Schafhitzel et al. (2007)
• Bruneton and Neyret (2008)

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CESCG09
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Outline

• Introduction
• Related work
• Model and its precomputation
• Rendering
• Results
• Conclusion
• Interactive demonstration

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CESCG09
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Scattering model
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CESCG09
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Scattering model
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CESCG09
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Precomputation

• We need scattering for
• Every position
• Every view direction
• Every sun direcion

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CESCG09
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Precomputation

• We need scattering for
• Every position
• Every view direction
• Every sun direcion
• Naïve implementation - 9 DoF!

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CESCG09
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Precomputation

• We need scattering for
• Every position
• Every view direction
• Every sun direcion
• Naïve implementation - 9 DoF!
• Improved parametrization
• Polar coordinates
• Observer altitude
• Without azimuth

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CESCG09
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Precomputation

• We need scattering for
• Every position
• Every view direction
• Every sun direcion
• Naïve implementation - 9 DoF!
• Improved parametrization
• Polar coordinates
• Observer altitude
• Without azimuth

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CESCG09
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Multiple scattering
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CESCG09
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Multiple scattering

• Computational complexity Ck(n2n3)k

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CESCG09
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Multiple scattering

• Computational complexity Ck(n2n3)k
• Higher scattering orders similar to IS for P

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CESCG09
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Multiple scattering

• Solution iterative computation
• Scattering texture contains previous order

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CESCG09
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Multiple scattering

• Solution iterative computation
• Scattering texture contains previous order

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CESCG09
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Multiple scattering

• Solution iterative computation
• Scattering texture contains previous order

• New complexity Cn2 (k-1)C(n2n3)
• n3 term now fast

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CESCG09
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Outline

• Introduction
• Related work
• Model and its precomputation
• Rendering
• Results
• Conclusion
• Interactive demonstration

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CESCG09
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Rendering

• On graphics hardware
• Fragment shader evaluation
• Simple spherical geometry
• Terrain taken into account in Schafhitzel et al.

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CESCG09
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Rendering

• On graphics hardware
• Fragment shader evaluation
• Simple spherical geometry
• Terrain taken into account in Schafhitzel et al.
• Atmosphere
• Evaluate h, ? and d
• Fetch sky colour
• Front face culling enabled

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CESCG09
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Rendering

• On graphics hardware
• Fragment shader evaluation
• Simple spherical geometry
• Terrain taken into account in Schafhitzel et al.
• Atmosphere
• Evaluate h, ? and d
• Fetch sky colour
• Front face culling enabled

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CESCG09
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Rendering

• Planet
• Scattering
• Direct illumination
• Water reflection
• Ambient light

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CESCG09
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Rendering

• Planet
• Scattering
• Direct illumination
• Water reflection
• Ambient light(precomputed in texture)

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CESCG09
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Rendering

• Planet
• Scattering
• Direct illumination
• Water reflection
• Ambient light(precomputed in texture)

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CESCG09
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Outline

• Introduction
• Related work
• Model and its precomputation
• Rendering
• Results
• Conclusion
• Interactive demonstration

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CESCG09
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Results

• 0.2x Earth atmosphere density

• 5x Earths atmosphere density

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CESCG09
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Results

• Single scattering

• Multiple scattering

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CESCG09
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Outline

• Introduction
• Related work
• Model and its precomputation
• Rendering
• Results
• Conclusion
• Interactive demonstration

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CESCG09
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Conclusion

• We present
• Precomputation scheme for multiple scattering in
  parametrizable atmosphere
• 5 MB for whole dataset
• Real-time rendering algorithm for entire planet
• 180 FPS _at_ 1024x768 (GeForce 8800GT)

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CESCG09
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Demonstration
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CESCG09
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End

• Thank you for your attention
• Questions?

Oskar Elek
CESCG09