https://bitbucket.org/simoncblyth/g4dae Exporter
Export any Geant4 Geometry into COLLADA/DAE standard 3D files, including:
- volume tree: physical volume/logical volume heirarchy
- geometry: vertices, triangles+quads
- materials and surfaces with properties as function of wavelength
https://bitbucket.org/simoncblyth/chroma Forked:
- Stability + efficiency improvements, enabling mobile development [2]
- Add recording of propagation steps into VBO [9] datastructure
- Animated visualization
| [2] | MacBook Pro (2013), NVIDIA GeForce GT 750M 2048 MB ; Workstation GPUs such as NVIDIA Kepler K20 expected at least ~3x faster |
Chroma Raycasting : exercises geometry intersection
Raycasting exercises slowest part of optical photon propagation: geometry intersection.
- Shoot rays thru every pixel out into geometry, 1 CUDA thread for each, typically >1M rays
- Find triangle intersections using BVH [3] acceleration structure
- Determine color based on ray to triangle normal angle
- Alpha blend nearest 10 surfaces, providing transparency effect
| [3] | Boundary Volume Heirarchy, a tree of bounding boxes with triangles inside leaf nodes |
Chroma Raycast Worst Case (~entire geometry) Example
Render Split into 3x3 CUDA kernel launches, 1 thread per pixel, ~1.8s for 1.23M pixels, 2.4M tris.
g4daeview.py --target=.. --eye="-0.3,-1.1,1.7" --look="0.1,0.4,-0.6" --up="1.2,2.0,1.6" --size=1440,852 --near=30.00000 --far=10000.0 --yfov=50.0 --with-chroma
Chroma Raycast Triangle count (Dyb with RPC)
g4daeview.py --with-chroma --metric tri --flags 1,0 # tri/time/intersect
All triangle intersections made, even when no visible contribution to render. (Potential for optimisation?)
g4daeview.py : Dayabay Chroma Photon Propagation
Chroma GPU photon propagation at 12 nanoseconds. The photons are generated by Geant4 simulation of a 100 GeV muon travelling from right to left. Photon colors indicate reemission (green), absorption(red), specular reflection (magenta), scattering(blue), no history (white).
g4daeview.py : Dayabay Chroma Photon Propagation
Chroma GPU photon propagation at 14 nanoseconds. The interface provides interactive control of the propagation time allowing any stage of the propagation to be viewed by scrubbing time backwards/forwards. The speed of this visualization is achieved by interoperation of CUDA kernels and OpenGL shaders accessing the same GPU resident photon propagation data.
g4daeview.py : Photon Selection Interface
Propagation steps OR photons can be selected by materials, propagation history, or special selection by photon identifier. Photons can be selected by clicking their 3D representations allowing inspection of the propagation history of individual photons.
g4daeview.py : Propagation Step Selection Interface
Photon propagation steps with material pair GdDopedLS,Acrylic. The larger squares represent selected photons, providing access to numerical details of propagation history.
g4daeview.py : Individual Photon Selection
Propagation steps of a single photon, the steps at either sides of the inner and outer acrylic vessels are visible. The line color represents the photon history starting white and turning magenta following a specular reflection.
g4daeview.py : Initial Photon Positions
Initial photon positions of a Geant4 simulated muon that crosses between the Dayabay Near hall ADs. Colors represent photon wavelengths.
g4daeview.py : OpenGL view of Juno Geometry
External view of Juno geometry with cutaway. The extreme size of the Juno geometry (50 million nodes in Chroma representation) provides a challenge for development on mobile GPUs. As my developments operate at the Geant4 level wherever possible it was relatively straightforward to apply the machinery developed for Dayabay to the Juno detector. In collaboration with Juno simulation experts the geometry was exported from Geant4 and GPU visualized in under a days work.
g4daeview.py : Chroma Raycast of Juno Geometry
External view of Juno geometry. The extreme size of the Juno geometry (50 million nodes in Chroma representation) provides a challenge for development on mobile GPUs. The black rectangle arises due to aborts to avoid GPU crashes.
G4DAE Dayabay Near Site
OSX Preview.app render
G4DAE Dayabay AD
OSX Preview.app render
Chroma Ray Tracing Dayabay Geometry (1)
Chroma Ray Tracing Dayabay Geometry (2)
Chroma Ray Tracing Dayabay Geometry (3)
Chroma Ray Tracing Dayabay Geometry (4)
