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Orion Sky Lawlor, Jon Genetti University of Alaska Fairbanks 2011-02-01 http://www.cs.uaf.edu/. Interactive Volume Rendering Aurora on the GPU. 8. Structure of talk: (1) What are the Aurora? (2) How do we represent Aurora on the GPU? (3) How do we render Aurora efficiently? - PowerPoint PPT Presentation
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Interactive Volume Rendering Aurora on the GPU
Orion Sky Lawlor, Jon GenettiUniversity of Alaska Fairbanks
2011-02-01
http://www.cs.uaf.edu/
8
Structure of talk:(1) What are the Aurora?
(2) How do we represent Aurora on the GPU?
(3) How do we render Aurora efficiently?
(4) How do we render Aurora on a powerwall?
(5) Conclusions & future work
(1) What are the Aurora?
Charged particles from the Sun
Image credit: NASA
Particles intersect Magnetosphere
Image credit: Wikipedia
What are the Aurora?Sheets of electrons coming down
Earth's magnetic field lines, and
hitting the upper atmosphere
What are the Aurora?electrons: 1-20kV, millions of amps
magnetic field: inclined to surface
atmosphere: 50-500km up
Aurora: Best Viewed From Orbit
Image credit: NASA (ISS)
(2) Representing Auroraon the GPU
Prior Aurora Representations
Nonphysical hacks [e.g., screensavers] 100% phemonological No planet, no units, no atmosphere, etc. But it looks good
Individual Charged Particles [Baranoski, Rokne, et al] Easy to physically transport through magnetosphere Nearly zero data storage requirements Difficult to render from arbitrary viewpoint (sampling!)
Volume-Rendered Voxel Grid [Genetti] Easy to render from arbitrary viewpoint (raycasting) 10000 km * 10000 km * 500 km thick = serious RAM! Only feasible with hierarchical storage (slow render)
Our Aurora Representation
Factor 3D aurora display into 2D * height 2D is electron intensity map: “curtain footprints”
Stored as 163842 2D texture (polar coordinates) Currently generated with phenomological fluid hack Working on output from a real HPC simulation
Height-dependent electron deposition function Given electron intensity and height, return emission Also stored as a 2D texture, 10242
Computed from particle scattering laws [Lazarev] Uses MSIS upper atmosphere model
Auroral electrons are moving at relativistic speeds (60000 km/s for 10KeV), so this approximation is quite accurate
2D Curtain Footprints: Fluids Hack
Deposition Function: MSIS Atmosphere
Deposition Function vs Altitude
“Height” includes Magnetic Inclination
(3) Speeding up Rendering
Explicit list of compositing orders
Don't use Recursive Raytracing!
Begin with 2D Curtain Footprints
Build Distance Field to find Curtains
Algorithm:Jump Flooding[Rong & Tan]
Algorithm:Proximity Clouds[Cohen & Sheffer]
Use Distance Field to Render Curtains
Measured “Performance Image”
White = 200ns/pixel Black = 10ns/pixel
Compounding Speedups
Factor 3D into 2D + height: 2xUse GPU instead of CPU: 100xNon-recursive raytracer: 3xDistance field acceleration: 3.5x
Old version: 10 minutes/frame
New version: 20-60 frames/sec
(4) MPIglut &
1x109 rays/second
Powerwall Aurora Rendering
Sequential OpenGL Application
Parallel Powerwall Application
Compounding Speedups
Factor 3D into 2D + height: 2xUse GPU instead of CPU: 100xNon-recursive raytracer: 3xDistance field acceleration: 3.5xUse ten GPUs with MPIglut: 8x
Old version: 10 minutes/frame @ 1080p
New version: 30 frames/sec @ 8400x4200
Powerwall Aurora Rendering
Demo Movie
(5) Future Work:Moving curtains!
Red slow-glow
Terrain Geometry
Clouds & Sunrise
Planetarium Show
Questions?