Perceptual Science Series

Ecological optics of natural materials
Sylvia Pont
Dept. of Physics and Astronomy, Program Human Perception, Helmholtz Institute

Wednesday, May 28, 2003 at 1:00 pm, RuCCS A139

Dr. Sylvia Pont

Dept. of Physics and Astronomy, Program Human Perception, Helmholtz Institute


Ecological optics of natural materials

Why does skin look soft? How can we change forward into backward reflectors? Why did Galileo judge the depth of the craters on the moon from craters positioned near the shadow edge? How can we estimate whether an orange is illuminated by direct sunlight or by an overcast sky from it�s texture? What causes double specular reflections in woven materials?

In order to answer questions like these I investigate the optical properties
of natural scenes ("ecological optics") and, more specifically, of the
materials in such scenes. One of my long-term goals is to investigate human
perception of natural materials in complex light fields. The appearance of
natural materials is dependent on the properties of the light field and on
the optical properties of the materials, which are affected by the bulk
constitutions, interfaces, three-dimensional texture or surface
corrugations, shape and the scale at which observers look at the materials.

I will present work on bidirectional reflectance distribution functions
(BRDF�s) for specific materials such as silk and velvet, and BRDF�s of
canonical surfaces (surfaces with spherical pits). Besides the work on
reflectance properties, I will discuss studies into statistical descriptions
of 3D textures: the bidirectional texture contrast function and estimates of
illumination direction from texture.



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