Title: High-Level User Interfaces for Transfer Function Design with Semantics
1High-Level User Interfacesfor Transfer Function
Design with Semantics
- Christof Rezk Salama (Univ. Siegen , Germany)
- Maik Keller (Univ. Siegen, Germany)
- Peter Kohlmann (TU Vienna, Austria)
2Volume Visualization
- Volume visualization techniques are mature from
the technical point of view. - Real-time volume graphics on commodity PC
hardware - Multidimensional transfer functions/classification
- Gradient estimation and local illumination
on-the-fly - Memory management and compression for large
volumes - Even global illumination techniques.
- Is the volume rendering problem solved?
- If you ask the computer scientist, hell probably
say yes. - If you ask the users, they will most likely say
no
3Questions
- Why are volume rendering applications so hard to
use for non-experts? - Are volume rendering applications easy to use for
us, the experts ? - What features must appropriate user interfaces
provide?
4The Mental Model
Example taken from Donald A. Norman The
Psychology of Everyday Things
5Volume Visualization
- Transfer Function Design Mapping of scalar data
to optical properties (emission/absorption) - Color table Example 1D TF for 12 bit Data,
4096 values x RGBA 16384 DOF - Editors based on geometric primitives
2D Transfer Functions
1D Transfer Functions
6User Intention
- Examples
- Fade out the soft tissue
- Sharpen the blood vessels
- Enhance the contrast
- Question What actions are necessary?
- Even the expert, who programmed the user
interface, doesnot know this! - Mental model is inappropriate or missing!
- Semantics are missing (leads to gulf of
execution) - Result in trial-and-error
7Abstraction Levels
All previous approaches aim at reducing the
complexity, the degrees of freedom.
None of the prevous approaches tries to provide
an appropriate mental model!
8Semantic Models
- Restrict ourselves to one specific application
scenario.Example CT angiography from
neuroradiology - The visualization task will be performed manually
for multiple data sets.Visualization expert and
medical doctor! - Evaluate statistical information about the
results - Which parameter modifications are necessary to
make the blood vessels sharper? - Use dimensionality reduction (PCA) to create a
semantic model
9Developing a Semantic Model
Step 1 Create a template for the TF
10Developing a Semantic Model
Step 2 Adapt the template to reference data
11Developing a Semantic Model
Step 2 Adapt the template to reference data
12Developing a Semantic Model
Step 2 Adapt the template to reference data
Step 3 Dimensionality reduction
Reference Transfer Functions
Semantic Model
13Semantic Model
High-Level User Interface
Transfer Function
Semantic Model
14Semantic Model
15Prototype Implementation
- Applicable to anything that can be described by
a parameter vector - Take care of the scale!
- PCA for entire parameter vector is not
appropriate - Small details might be missed
- Our solution
- Split transfer function into entities
(structures, groups of primitives with same
scale) - Perform PCA separately for each entity
- Reassemble the transfer function from the
different entities
16Results
- CTA intracranial aneurysms
- 512 x 512 x 120-160 _at_12bit, 100ml non-ionic
contrast dye - 20 data sets for training / 5 data sets for
evaluation - MR brain surgery
- 256 x 256 x 150-200 _at_12bit (noisy, lower
dynamic range 10bit) - 10 data sets
- Evaluation of the model
- Analytically Stability of the eigenvectors (dot
product gt 0.9) - Stable for gt12 data sets (regardless of
individual choice) - User Study Labels removed from the user
interface - Most semantics were correctly identified by
non-expert users
17Conclusion
- User Interface Design Strategies
- Reducing DOF is not enough.
- Good user interfaces must provide an appropriate
mental model - Not an attempt to create a single user interfaces
for any visualization tasks - Create semantic models for examination tasks as
specific as necessary - Building block for software assistants for
medical diagnosis and therapy planning
18Acknowledgements
- Bernd Tomandl MD, Neuroradiologie, Bremen
- Christopher Nimsky MD, Neurochirurgie, Erlangen