visualization challenges for large scale astrophysical
TRANSCRIPT
![Page 1: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/1.jpg)
Ultrascale Visualization WorkshopNovember 13, 2011
Seattle, WA
Ralf Kähler (KIPAC/SLAC)
Tom Abel (KIPAC/Stanford)Marcelo Alvarez (CITA)Oliver Hahn (Stanford)
Hans-Christian Hege (ZIB)Ji-hoon Kim (KIPAC)
Stuart Marshall (SLAC) Matthew Turk (Columbia) Risa Wechsler (Stanford)John Wise (Georgia Tech)
Visualization Challenges for Large Scale Astrophysical Simulation Data
![Page 2: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/2.jpg)
COMPUTATIONAL ASTROPHYSICS
COMPUTATIONAL PHYSICS DEPARTMENT
Evolution of First Galaxies
Re-ionization EpochLarge-Scale Structure Formation
Evolution of First StarsSimulation: Wise & Abel
Simulation: Wu, Hahn & Wechsler
Simulation: Kim & Abel
Simulation: Alvarez & Abel
![Page 3: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/3.jpg)
![Page 4: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/4.jpg)
![Page 5: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/5.jpg)
Large-Scale Structure FormationSimulation: Wu, Hahn & Wechsler
![Page 6: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/6.jpg)
Evolution of First Stars
Evolution of First GalaxiesSimulation: Kim & Abel
Simulation: Turk & Abel
![Page 7: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/7.jpg)
Reionization EpochSimulation: Alvarez & Abel
![Page 8: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/8.jpg)
Numerical Astrophysics
High dynamical range
![Page 9: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/9.jpg)
Numerical Astrophysics
High dynamical range
Formation of First Stars
- Protogalaxy > 10,000 light years
Simulation: T. Abel
![Page 10: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/10.jpg)
Numerical Astrophysics
High dynamical range
Formation of First Stars
- Protogalaxy > 10,000 light years
- Protostar ~ 10 solar radii
Simulation: T. Abel
![Page 11: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/11.jpg)
Numerical Astrophysics
> 10 spatial orders of magnitude
Simulation: T. Abel
![Page 12: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/12.jpg)
STRUCTURED ADAPTIVE MESH REFINEMENT
Simulation Data: Tom Abel
![Page 13: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/13.jpg)
TEMPORAL REFINEMENT
AMR schemes perform refinement in time
Stability condition for solvers:
- Δt proportional to Δx
- global Δt determined by smallest Δx
➔ Computational overhead on coarse levels
![Page 14: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/14.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 15: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/15.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 16: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/16.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 17: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/17.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 18: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/18.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 19: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/19.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 20: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/20.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 21: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/21.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 22: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/22.jpg)
TEMPORAL REFINEMENT
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 23: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/23.jpg)
enzo - Adaptive Mesh Refinement
enzo
- Astrophysical Adaptive Mesh Refinement code
- Cosmological structure formation simulations
http://code.google.com/p/enzo/
![Page 24: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/24.jpg)
DATA SIZES
10-40 levels of refinement
10,000-100,000 time steps
up to 100 million patches
- less than 32^3 cells per patch
up to billions of cells per time step
- different fields ( gas density, gas temperature, etc. )
10s of TByte of data
![Page 25: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/25.jpg)
VISUALIZATION SOFTWARE
C++, JavaScript
Graphical User Interface (Qt)
OpenGL
Available as Open Source soon
Simulation data: Kim & Abel
![Page 26: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/26.jpg)
VISUALIZATION SOFTWARE
Simulation data: Kim & Abel
Modular Design: add vis-routines & readers
Readers for Enzo, Gadget, RAMSES
![Page 27: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/27.jpg)
VISUALIZATION SOFTWARE
Modular Design: add vis-routines & readers
Readers for Enzo, Gadget, RAMSES
Data nodes:Grid-based (AMR)Point-based (unstructured)Image data Simulation data: Kim & Abel
![Page 28: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/28.jpg)
VISUALIZATION SOFTWARE
Visualization methods:
Simulation data: Kim & Abel
![Page 29: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/29.jpg)
VISUALIZATION SOFTWARE
Real-Time Rendering:OpenGL & OpenGL Shading Language
Customize rendering at run-time by modifying OpenGL Shaders
Simulation data: Kim & Abel
![Page 30: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/30.jpg)
VISUALIZATION SOFTWARE
Visualization methods:SlicingDirect Volume RenderingStreamlines...
![Page 31: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/31.jpg)
VISUALIZATION SOFTWARE
Visualization methods:SlicingDirect Volume RenderingStreamlines...
Simulation Data: Mike Norman
![Page 32: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/32.jpg)
VISUALIZATION SOFTWARE
Visualization methods:SlicingDirect Volume RenderingStreamlines...
Simulation Data: John Wise & Tom Abel
![Page 33: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/33.jpg)
VISUALIZATION SOFTWARE
Visualization methods:SlicingDirect Volume RenderingStreamlines...
Simulation Data: Ji-hoon Kim & Tom Abel
![Page 34: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/34.jpg)
VISUALIZATION SOFTWARE
Visualization methods:SlicingDirect Volume RenderingStreamlines...
Simulation Data: Wu, Hahn & Wechsler
![Page 35: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/35.jpg)
Pre-Rendering for American Museum of Natural History Show “The Big Bang”, Narrated by Liam NeesonSimulation data: Ji-hoon Kim (Stanford), Tom Abel (Stanford/SLAC)
![Page 36: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/36.jpg)
DATA ACCESS PATTERNS
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 37: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/37.jpg)
DATA ACCESS PATTERNS
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 38: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/38.jpg)
DATA ACCESS PATTERNS
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 39: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/39.jpg)
DATA ACCESS PATTERNS
0 1 2 3 4 TIME
Level 0
Level 1
Level 2
![Page 40: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/40.jpg)
Generation of Proxy-Grid Structure
Time A Time B
![Page 41: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/41.jpg)
Generation of Proxy-Grid Structure
Time A Time B
![Page 42: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/42.jpg)
Generation of Proxy-Grid Structure
Time A Time B
![Page 43: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/43.jpg)
Generation of Proxy-Grid Structure
Time A Time B
![Page 44: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/44.jpg)
Generation of Proxy-Grid Structure
![Page 45: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/45.jpg)
DATA STORAGE
HDF5 for data I/O
- http://www.hdfgroup.org/HDF5/
Enzo HDF5 output
- each processor writes stream of separate HDF5 groups
- no spatial or temporal relations
GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { .... } ATTRIBUTE "level" { .... } ... DATASET "Density" { ... } DATASET "Temperature" { ... } ...}
GROUP "grid-1" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { .... } ATTRIBUTE "level" { .... } ... DATASET "Density" { ... } DATASET "Temperature" { ... } ...}
GROUP "grid-n" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { .... } ATTRIBUTE "level" { .... } ... DATASET "Density" { ... } DATASET "Temperature" { ... } ...}...
![Page 46: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/46.jpg)
HDF5 INDEX FILE
Post-processing:
- create HDF5 index file
- match the AMR grid structure
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
![Page 47: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/47.jpg)
HDF5 INDEX FILE
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
available time steps
![Page 48: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/48.jpg)
HDF5 INDEX FILE
time groups
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
![Page 49: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/49.jpg)
HDF5 INDEX FILE
level groups
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
![Page 50: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/50.jpg)
HDF5 INDEX FILE
grids on this level
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
![Page 51: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/51.jpg)
HDF5 INDEX FILE
grid meta data
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
![Page 52: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/52.jpg)
HDF5 INDEX FILE
previous & next time steps
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
![Page 53: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/53.jpg)
HDF5 INDEX FILE
links to datasets
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... } ... } GROUP "level-2" { ... } ... } GROUP "time-1" {
...
}
![Page 54: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/54.jpg)
HDF5 INDEX FILE
HDF5 "./rho.a5" {
GROUP "/" {
GROUP "globalMetaData" { DATASET "times" { ... } DATASET "timesteps" { ... }
... }
GROUP "time-0" { GROUP "level-0" {
ATTRIBUTE "predecessor" { ... } ATTRIBUTE "successor" { ... } } GROUP "level-1" { GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } … } GROUP "grid-1" { ATTRIBUTE "origin" { ... }
ATTRIBUTE "dims" { ... } ATTRIBUTE "data_reference" { ... } ... }
GROUP "grid-0" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { .... } ATTRIBUTE "level" { .... } ... DATASET "Density" { ... } DATASET "Temperature" { ... } ...}
GROUP "grid-1" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { .... } ATTRIBUTE "level" { .... } ... DATASET "Density" { ... } DATASET "Temperature" { ... } ...}
GROUP "grid-n" { ATTRIBUTE "origin" { ... } ATTRIBUTE "dims" { .... } ATTRIBUTE "level" { .... } ... DATASET "Density" { ... } DATASET "Temperature" { ... } ...}...
links to datasets
![Page 55: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/55.jpg)
POSTGRES DATABASE
Alternative:
- Index-structure via databases
Meta data in database, data (fields) in original HDF5 files
QtSQL Module: http://doc.qt.nokia.com/4.7/qtsql.html
PostgreSQL plugin
![Page 56: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/56.jpg)
COMPARISON
File sizes
- Postgres database ~ 20% of HDF5 index file
Metadata access
- Postgres twice as fast as HDF5
![Page 57: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/57.jpg)
GPU-Assisted Ray Casting
[Stegmaier, et al. 2005]
Input data ➔ 3D texture
Render front faces
Fragment Shader for each covered pixel:
Compute ray-direction
Sampling and color mapping
Resulting intensities --> frame buffer
![Page 58: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/58.jpg)
GPU-Assisted Ray Casting for AMR Data
Problem: Overlapping regions
➤ Decomposition of data domain
Adaptive kD-tree
- Nodes represent of non-overlapping blocks of cells
- View-dependent sorting (front-to-back or back-to-front)
![Page 59: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/59.jpg)
GPU-Assisted Ray Casting for AMR Data
View-dependent selection of nodes:
- Resolution level based on distance to viewpoint
~200,000 nodes ~20,000 nodes
![Page 60: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/60.jpg)
Simulation data: John Wise (Georgia Tech), Tom Abel (Stanford/KIPAC)
![Page 61: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/61.jpg)
Pre-Rendering for California Academy of Sciences, Dome Show “Life: A Cosmic Journey”, Narrated by Jodie Foster, November 2010Simulation data: John Wise (Princeton), Tom Abel (Stanford/SLAC)
![Page 62: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/62.jpg)
POINT-BASED DATASETS
Unstructured point datasets
- Dark matter density
- Single stars and star clusters
- ...
Point attributes
- Position
- Mass
- Age
- Accretion rate
- ...
Simulation: Wu, Hahn & Wechsler
![Page 63: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/63.jpg)
Solution for “opaque” point representation
1. Pass
Enable depth-buffer updates
Render points
2. Pass
Perform ray-tracing up to pixels depth value
3. Blending step
GPU-Raycasting of Combined Grid- and Point-based Data
![Page 64: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/64.jpg)
GPU-Raycasting of Combined Grid- and Point-based Data
Usually semi-transparent point representation
gaussian opacity profile for galaxies, stars, DM, etc.
Potential solution:
Resampling of point data to grid structure
Simultaneous rendering of both (grid) data sets
![Page 65: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/65.jpg)
GPU-Raycasting of Combined Grid- and Point-based Data
Requires highly resolved grids
High (texture-)memory consumption
and/or sacrifices data resolution
Low-pass filtering
Rendering artifacts
![Page 66: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/66.jpg)
GPU-Raycasting ofCombined Grid- and Point-based Data
• Point data ➤ Octree structure- Efficient GPU-representation- Implicit bounding-box information
• Recursive refinement of octree nodes
• Stopping criteria- Number of inserted points < threshold
![Page 67: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/67.jpg)
Combining Grid and Point Data
Node texture
3D-RGBA texture
One texel per node
Alpha-channel stores node type
Internal node Leaf node
RGB-channel
Index of first child node Index into data texture
Simulation: Alvarez & Abel
![Page 68: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/68.jpg)
Combining Grid and Point Data
Data texture
3D-RGBA floating point
RGB-channels: center
Alpha-channel: radius
Radius=0 indicates end of list
Simulation: Alvarez & Abel
![Page 69: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/69.jpg)
GPU-Raycasting of Combined Grid- and Point-based Data
1. Grid data ➤ 3D-texture
2. Point set ➤ two 3D-textures (GPU-octree representation)
3. Render front faces of bounding box
4. In Fragment shader
• Compute ray-direction
• Sampling of grid-based data
• Sampling of point-based data
• Combination of partial intensities
• Combination with total intensity
5. Resulting intensity ➤ frame-buffer
![Page 70: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/70.jpg)
Combined Point & Grid Raycasting
Summation of Intensities
• Relation between opacity and extinction coefficient
• Combination of opacities for segment si
• Combination with accumulated intensity/opacity of ray
![Page 71: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/71.jpg)
Combined Point & Grid Raycasting
Performance Optimizations
• Example: Gaussian profiles
![Page 72: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/72.jpg)
Combined Point & Grid Raycasting
Performance Optimizations
• ROI around camera location
![Page 73: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/73.jpg)
Combined Point & Grid Raycasting
Performance Optimizations
• Point and grid data inside ROI rendered with GPU approach
![Page 74: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/74.jpg)
Combined Point & Grid Raycasting
Performance Optimizations
• Outside ROI: - Process grid data until depth of first pass- blending with point splats
![Page 75: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/75.jpg)
Combined Point & Grid Raycasting
Performance Optimizations
![Page 76: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/76.jpg)
Combined Point & Grid Raycasting
Performance Optimizations
• Correct result if only one splat hit by ray outside ROI
![Page 77: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/77.jpg)
Combined Point & Grid Raycasting
Performance Optimizations
• Partially incorrect depth sorting for more than one splat• Artifacts usually not visible in far-field
![Page 78: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/78.jpg)
Combined Point & Grid Raycasting
Comparison of Rendering Quality
ROI = 0% of volume ROI = 25% of volumeROI = 100% of volume
Simulation: Alvarez & Abel
![Page 79: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/79.jpg)
Combined Point & Grid Raycasting
Numerical Simulation: Marcelo Alvarez (CITA), Tom Abel (KIPAC/Stanford)
![Page 80: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/80.jpg)
Combined Point & Grid Raycasting
Numerical Simulation: Marcelo Alvarez (CITA), Tom Abel (KIPAC/Stanford)
![Page 81: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/81.jpg)
Numerical Simulation: Marcelo Alvarez (CITA), Tom Abel (KIPAC/Stanford)
![Page 82: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/82.jpg)
Numerical Simulation: Marcelo Alvarez (CITA), Tom Abel (KIPAC/Stanford)
![Page 83: Visualization Challenges for Large Scale Astrophysical](https://reader034.vdocuments.us/reader034/viewer/2022042214/625992129ef83c248f208fe6/html5/thumbnails/83.jpg)
Visit us as the SLAC booth (303) and watch some visualizations in 3D !