Usage of volume rendering techniques in Chemitry and Medicine V3D2 Workshop 2002, Braunschweig, Strategic DFG research initiative "V3D2" ("Distributed Processing and Exchange of Digital Documents")

1. Pre-Integrated Volume-Rendering
with
Randomized Transfer-Functions
Klaus Engel, Guido Reina, Thomas Ertl
Klaus Engel, Guido Reina, Thomas Ertl
Abteilung Visualisierung und Interaktive Systeme
Abteilung Visualisierung und Interaktive Systeme
Universität Stuttgart
Universität Stuttgart
Frank Oellien, W.D. Ihlenfeldt
Frank Oellien, W.D. Ihlenfeldt
Computer Chemie Centrum
Computer Chemie Centrum
Universität Erlangen-Nürnberg
Universität Erlangen-Nürnberg
V3D2 Symposium 21./22. Februar 2002

2. Volume Data Sources
Measurements
(cryo-electron
microscopy)
Binning of
multi-variate data
Computed data
(molecular orbitals)
Simulations
(convection flow)
Synthetic data
(radial distance volume
+ Perlin Noise)
V3D2 Symposium 2002 - ChemVis Project

3. Volume Rendering - Physical Model
• Physics of light transport
• Simplified to Volume Rendering Integral
I ( s) = I ( s0 )e
−τ ( s0 , s )
s2
s
+ ³ q( s' ) ⋅ e
−τ ( s ', s )
ds'
s0
τ ( s1, s2 ) = ³ κ ( s)ds
s1
• Transfer Function:
Assigns opacity and color
•
s
s0
• Discretization
n
j =i +1
d
d
d
n
i =0
d
I (sn ) = ¦ Ciα i ∏ (1 − α j )
s1
V3D2 Symposium 2002 - ChemVis Project
sn

4. Texture-based Volume Rendering
2D textures
(axis-aligned
slices)
texturing
(bilinear
interpolation)
compositing
(blending)
texturing
(trilinear
interpolation)
compositing
(blending)
3D textures
(view-aligned
Slices)
V3D2 Symposium 2002 - ChemVis Project

5. Volume Rendering - Classification
Classification
Interpolation
Transfer-Functions
Pre-Classification
Voxel
Interpolation
Classification
Post-Classification
V3D2 Symposium 2002 - ChemVis Project

6. Higher Sampling Rates
Cryoelectron-microscopic Volume
Isosurface of Escherichia Coli Ribosome at 18 Ångström
All data slices
V3D2 Symposium 2002 - ChemVis Project
10 times more slices

7. Higher Sampling Rates – Problem
• Discrete Approximation of Volume Rendering
Integral will converge to correct result for d→0
– According to Sampling Theorem sampling rate must be
greater than the Nyquist frequency
– But: High frequencies in the Transfer Function may
considerably increase the required sampling rate
• Pre-Integrated Volume Rendering
– Idea: Split numerical integration into
• one pre-integration for the transfer function
• one integration for the scalar field
– Pre-Integrate Ray-Segments in a pre-processing step
V3D2 Symposium 2002 - ChemVis Project

8. Pre-Integrated Volume Rendering
slice-by-slice
slab-by-slab
project slice
sf sb
texture
polygon
pre-integrate all
fetch integral from
possible combinations s dependent texture
b
sb
sf sb
sf
sf
front back
slice slice
hardware-accelerated
implementation
on NVidia NV20
and ATI R200
chips
V3D2 Symposium 2002 - ChemVis Project

9. Single Peaked Transfer-Functions
V3D2 Symposium 2002 - ChemVis Project

10. Multi-Peak Transfer-Functions
V3D2 Symposium 2002 - ChemVis Project

11. Randomized Transfer-Functions
V3D2 Symposium 2002 - ChemVis Project

12. Randomized Transfer-Functions
V3D2 Symposium 2002 - ChemVis Project

13. Results – Classification schemes
Pre-Classification
Post-Classification
Pre-Integrated-Classification
V3D2 Symposium 2002 - ChemVis Project

14. Results - OrbVis
V3D2 Symposium 2002 - ChemVis Project

15. Results – Randomized Transfer Functions
V3D2 Symposium 2002 - ChemVis Project

16. Results – Randomized Transfer Functions
V3D2 Symposium 2002 - ChemVis Project

17. Results – Randomized Transfer Functions
V3D2 Symposium 2002 - ChemVis Project

18. Conclusions
• Pre-Integrated Volume Rendering
–
–
–
–
hardware-accelerated Implementation
integration into digital documents ?
reproduces high frequencies in the TFs
ideally suited for random TFs
• Randomized Transfer Functions
– a new visualization technique for volume data
– somehow related to LIC
– visualizes “all” isosurfaces at the same time
V3D2 Symposium 2002 - ChemVis Project

19. InfoVis - Previous Work
VRML-based NCI Database Interface
detailed
structure
information
substructure
search
NCI
anti-viral
anti-tumor
database
results
toxicity (LD50) of chemical
compounds against breast
cancer cell lines
V3D2 Symposium 2002 - ChemVis Project

20. Current Work
InfVis Applet I
Tool Panel
Java3D
Canvas
(filters,
selection
tools,
details)
Control
Panel
Glyph-based
(details)
+
volumetric
(overview)
V3D2 Symposium 2002 - ChemVis Project

21. Future Worker
Guido Reina: „Visualisierung und Manipulation großer Graphen
in einem Graphical User Interface am Beispiel der zSeries
I/O-Topologie”
V3D2 Symposium 2002 - ChemVis Project