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

Motivation Why atmosphere? Oskar Elek CESCG’09

Motivation Why real-time? Oskar Elek CESCG’09

Outline Introduction Related work Model and its precomputation Rendering Results Conclusion Interactive demonstration Oskar Elek CESCG’09

Outline Introduction Related work Model and its precomputation Rendering Results Conclusion Interactive demonstration Oskar Elek CESCG’09

Introduction Participating media Oskar Elek CESCG’09

Introduction Participating media Light scattering Rayleigh / Mie Multiple scattering Oskar Elek CESCG’09

Introduction Participating media Light scattering Parametrizability Rayleigh / Mie Multiple scattering Parametrizability Oskar Elek CESCG’09

Outline Introduction Related work Model and its precomputation Rendering Results Conclusion Interactive demonstration Oskar Elek CESCG’09

Related work Scattering physics Non-realtime methods Real-time methods 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) Oskar Elek CESCG’09

Outline Introduction Related work Model and its precomputation Rendering Results Conclusion Interactive demonstration Oskar Elek CESCG’09

Scattering model Oskar Elek CESCG’09

Scattering model Oskar Elek CESCG’09

Precomputation We need scattering for: Every position Every view direction Every sun direcion Oskar Elek CESCG’09

Precomputation We need scattering for: Naïve implementation - 9 DoF! Every position Every view direction Every sun direcion Naïve implementation - 9 DoF! Oskar Elek CESCG’09

Precomputation We need scattering for: Naïve implementation - 9 DoF! Every position Every view direction Every sun direcion Naïve implementation - 9 DoF! Improved parametrization Polar coordinates Observer altitude Without azimuth Oskar Elek CESCG’09

Precomputation We need scattering for: Naïve implementation - 9 DoF! Every position Every view direction Every sun direcion Naïve implementation - 9 DoF! Improved parametrization Polar coordinates Observer altitude Without azimuth Oskar Elek CESCG’09

Multiple scattering Oskar Elek CESCG’09

Multiple scattering Computational complexity Ck*(n2+n3)k Oskar Elek CESCG’09

Multiple scattering Computational complexity Ck*(n2+n3)k Higher scattering orders – similar to IS for P Oskar Elek CESCG’09

… Multiple scattering Solution – iterative computation Scattering texture contains previous order … Oskar Elek CESCG’09

… Multiple scattering Solution – iterative computation + Scattering texture contains previous order … + Oskar Elek CESCG’09

… Multiple scattering Solution – iterative computation Scattering texture contains previous order … + New complexity C*n2 + (k-1)*C*(n2+n3) n3 term now fast Oskar Elek CESCG’09

Outline Introduction Related work Model and its precomputation Rendering Results Conclusion Interactive demonstration Oskar Elek CESCG’09

Rendering On graphics hardware Fragment shader evaluation Simple spherical geometry Terrain taken into account in Schafhitzel et al. Oskar Elek CESCG’09

Rendering On graphics hardware Fragment shader evaluation Simple spherical geometry Terrain taken into account in Schafhitzel et al. Atmosphere Evaluate h, θ and δ Fetch sky colour Front face culling enabled Oskar Elek CESCG’09

Rendering On graphics hardware Fragment shader evaluation Simple spherical geometry Terrain taken into account in Schafhitzel et al. Atmosphere Evaluate h, θ and δ Fetch sky colour Front face culling enabled Oskar Elek CESCG’09

Rendering Planet Scattering Direct illumination Water reflection Ambient light Oskar Elek CESCG’09

Rendering Planet Scattering Direct illumination Water reflection Ambient light (precomputed in texture) Oskar Elek CESCG’09

Rendering Planet Scattering Direct illumination Water reflection Ambient light (precomputed in texture) Oskar Elek CESCG’09

Outline Introduction Related work Model and its precomputation Rendering Results Conclusion Interactive demonstration Oskar Elek CESCG’09

Results 0.2x Earth atmosphere density 5x Earth’s atmosphere density Oskar Elek CESCG’09

Results Single scattering Multiple scattering Oskar Elek CESCG’09

Outline Introduction Related work Model and its precomputation Rendering Results Conclusion Interactive demonstration Oskar Elek CESCG’09

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 @ 1024x768 (GeForce 8800GT) Oskar Elek CESCG’09

Demonstration Oskar Elek CESCG’09

End Thank you for your attention Questions? Oskar Elek CESCG’09