1. Transfer Function Transfer functions make volume data visible
by mapping data values to optical properties
volume data

2. Transfer Function

3. Optical Properties
Anything that can be composited with a standard graphics operator (“over”)
Opacity: “opacity functions”
Most important
Color
Can help distinguish features
Emittance
Why don’t we use this more often?
Phong parameters (ka, kd, ks)
Index of refraction

4. Volume rendering with different transfer functions
Setting transfer function is difficult, unintuitive, and slow

5. Goal Make good renderings easier to come by
Make space of TFs less confusing
Remove excess “flexibility”
Provide one or more of:
Information
Guidance
Semi-automation
Automation

6. Multidimensional Transfer Fucntion Design

7. 1D vs 2D histogram

8. Volume rendering using 2D transfer function

9. Function f , and Derivatives f’ , f’’

10. Multidimensional transfer function

11. Interaction Tools Data Probe Clipping plane Classification Widget
Triangle
rectangle

12. Dual Domain Interaction

13. Results

14. Results