Semester project presentation of a statistical visualisation tool for exploring medical and geological volume data

1. Cuberilles – Statistical Volume Vis
INF252 Visualization – Final Project Presentation
Christian Kehl

2. Design Focus
 Coupled interaction Statistics  Volume
 statistical 2D views (Avg/Max Intensity Proj.)
 Statistics per Dimension
 1D ray: Histogram, Profile, Semi-Variog.
 2D slice: Histogram, Semi-Variogram
 3D volume: Histogram
 Convolution responses; Histogram –> PDF
Design Demo Specifics Reflection2

3. Design Focus
 3D representation using Cuberilles
 why ? data sharing GPU 3D – CPU
 Glyphing Cuberilles with Cubes or Spheres
 Preset Editor for Colour-Opacity changes
 Lensing for Zooming; separated 3D-2D view
 Focus: interaction & vis. mapping; sacrifice render
quality (no render styles or shadows; simple shading)
Design Demo Specifics Reflection3

4. Implementation Choices
 Dev Environment: Linux; hence Cross-Platform
 Java OpenGL (JOGL); no SceneGraph avail.
 Shaders in GLSL
 UI: SWT (native UI on each system)
 distribution via web (Java webstart) or binary
 Graphing library: SWT chart
 tryouts with modern OpenCL list sorts failed ...
Design Demo Specifics Reflection4

5. Demo
Design Demo Specifics Reflection5

6. Specifics – non-implemented features
 Focus+Context via lensing
 switch perspective/orthographic proj.
 Dataset comparison
 Glyphing: limited by render speed
 Probability distribution function (PDF)
 Convolution kernels
Design Demo Specifics Reflection6

7. Cuberilles
 OpenGL 2: triangle array too slow (call-bound);
blending problems
 OpenGL 3: geometry shader reduces to point
calls
 OpenGL 4: instanced rendering (not impl.)
 Geometry shader description of cube simple,
spheres demand more calls
 Cube: 6 triangle patches
 Sphere (6 vert., 12 horiz. resolution): 72 triangle p.
Design Demo Specifics Reflection7

8. Cuberilles
Design Demo Specifics Reflection8
12 yo laptop, GLES: 64x64x29
Lab PC, Quadro K4200, GL3: 512x512x232

9. Alpha Composition
 Problem: Render-order dependent composition
 depth peeling => small number of alpha layers
 tried pre-computed render orders (1 per
bounding box corner): didn’t really work ...
 Sorting: just points, not cube vertices
 Simple view-dependent sorting not interactive
 Parallel sorting improved speed reasonably
Design Demo Specifics Reflection9

10. Alpha Composition
Design Demo Specifics Reflection10
common alpha composition with x-y-z render order pre-computed, closest-corner render order
render order computed each frame

11. Normal/Gradient Visualisation
 Normal: divergent per dimension & between
positive/negative slope; defined 0-point
Design Demo Specifics Reflection11
full colour spectrum ->colour-
blind problem
divergent, too bright xy mapping+; z mapping - contrast-less; 0-value confuser
good contrast,
good highlights;
confuser:
N[0 0 1] = N[0 0 0]
divergent between x-y-z:
[magenta-blue-purple]
divergent to slope direction
with saturation:
[high-mid-low] = [-1 0 1]
0-value confuser possible
V-1 = I-1

12. Geological Datasets
 Geological facies datasets similar to CT (depict
structure)
 statistical exploration can help to spot rock
relationships
Design Demo Specifics Reflection12
porosity model depicts structure poorly facies model depicts structure very well

13. Lessons learned ...
 Cubrilles: possible, but not advisable (modern GPUs do
volume raycasting better)
 Statistics: helpful for exploring new datasets
 Lighting: highlights structure in volumes unexpectedly well
 GPU sorting: did improved; still not comparable to CPU
 Gradient/Normal Mapping: harder than it seems ...
 Volume Visualisation: it’s fun 
 “Lonely Rider” not advisable – a good team is better than
the sum of its individuals ...
And: thank you for the time to update my OpenGL
knowledge 
Design Demo Specifics Reflection13

14. River
Discharge
SAND
SILT
Searching for a summer or
semester job ?
Doing Volume Visualisation
in Geology ?
then THIS may be for you!
Delft3D Delta Modelling:
• WebVis using WebGL / osgjs
• detailed, time-dependent,
multi-variate VolumeVis
• teamwork with experienced
3D engineer as guide
• cool project, good team ... &
getting in touch with petroleum
Contact: Simon J. Buckley
simon.buckley@uni.no
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