1. Obtaining the Bidirectional Texture Reflectance of Human Skin by means of a Kaleidoscope Jude Radloff Research Project Presentation Supervised by Shaun Bangay and Adéle Lobb. Part of the Virtual Reality Special Interests Group (VRSIG). Computer Science Honours – Rhodes University 28 July 2004

2. Today’s Presentation Objective Background to reflectance measurement Introduction to the Kaleidoscope technique Investigation of various configurations – simulated Practical implementation Next step in research process Questions

3. Objective : Increased realism of simulated real-world surfaces. Ultimately human skin, being a highly complex surface. Currently focusing on preparation. Bidirectional Texture Function (BTF) describes how INCOMING light is REFLECTED OFF a surface, and how this VARIES over the surface BTF ( θi, Φi, θo, Φo, u, v ) NB light’s interaction with a surface

5. Han and Perlin, 2003 Proposed a novel technique in measuring reflectance by means of a kaleidoscope Kaleidoscope’s reflective properties allow a sample to be viewed from a variety of directions - without the need for mechanical movement. Potentially: »More economical (time / finance) »More accurate, because of less calibration »Simpler »Easier to use

6. Kaleidoscope System Setup

7. Investigation of configurations - by simulation Considerations : Field of View Levels of Reflection Number of Sides Angle of Taper Alternative Configurations –Non-tapered –Additional mirror(s) beneath sample

8. Taper causes interreflections, which results in a virtual sphere

9. In a non-tapered configuration, the result is a tiled sample image

10. Experimental configuration: Tapered cylinder – each level of reflection containing a single distorted image

11. Recent development : Physical implementation of selected configurations based on our findings in the AFRIGRAPH paper On display today : 3-sided non-tapered kaleidoscope 4-sided tapered kaleidoscope 4-sided tapered kaleidoscope with extended reflective base – this novel configuration is expected to result in an even richer BTF measurement

12. Next Step… Set up camera and projector as described in the Han and Perlin paper (2003). Build up BTF database of view-illumination pair digital images. VIEW ILLUMINATION

13. Questions?