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 University28 July 2004

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

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 )

NBlight’s interaction with a surface

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

Kaleidoscope System Setup

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

Taper causes interreflections, which results in a virtual sphere

In a non-tapered configuration, the

result is a tiled sample image

Experimental configuration:

Tapered cylinder – each level of

reflection containing a

single distorted image

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

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

ILLU

MIN

AT

ION

Questions?