1. University of Illinois at Chicago Electronic Visualization Laboratory (EVL) Multi-Dimensional Transfer Functions for Interactive Volume Rendering & Interactive Volume Rendering Using Multi- Dimensional Transfer Functions, etc. by Kniss, Kindlmann, Hansen University of Utah presentation by Nicholas Schwarz schwarz@evl.uic.edu Electronic Visualization Lab University of Illinois at Chicago

2. Electronic Visualization Laboratory (EVL) Introduction Easy to find objects in spatial domain, but difficult to do so in transfer function domain. Different regions may have same scalar value. Enormous degrees of freedom. Small changes in transfer function result in drastic/unexpected changes in the visualization.

3. University of Illinois at Chicago Electronic Visualization Laboratory (EVL) Multi-Dimensional Transfer Functions Gradient – local rate of change (1 st derivative)

4. University of Illinois at Chicago Electronic Visualization Laboratory (EVL) Multi-Dimensional Transfer Function Hessian – second partial derivative

5. University of Illinois at Chicago Electronic Visualization Laboratory (EVL) Multivariate Data

6. University of Illinois at Chicago Electronic Visualization Laboratory (EVL) Hardware Dependent texture reads: use color fragments to generate texture coordinates, replace those color fragments with corresponding entries from a texture. Classification: can get vary large for multi- dimensions, so higher dimensions are limited. Surface shading: cube map dependent texture reads – treat RGB component as a vector used as texture coordinates for a cub map. Bad for shading homogeneous regions, but good for boundaries.

7. University of Illinois at Chicago Electronic Visualization Laboratory (EVL) Hardware Shadows: off screen render buffer to accumulate the amount of light.

8. University of Illinois at Chicago Electronic Visualization Laboratory (EVL) Nifty Widget