Date and Time

Wednesday, March 13, 2002 - 4:00pm to 5:30pm

Location

Computer Science Small Auditorium (Room 105)

Type

Colloquium

Speaker

Ravi Ramamoorthi [1], from Stanford University

Host

Thomas Funkhouser

Website

Understanding the nature of reflection and illumination is important
in many areas of computer graphics and computer vision. In this talk, I
describe a new way of looking at reflection on a curved surface, as a
special type of convolution of the incident illumination and the reflective
properties of the surface (technically, the bi-directional reflectance
distribution function or BRDF). We formalize these notions by
deriving a convolution theorem in terms of the spherical harmonic
coefficients of the lighting and BRDF. This allows us to introduce a
signal-processing framework for reflection, wherein the incident
lighting is the signal, the BRDF is the filter, and the reflected
light is obtained by filtering the input illumination (signal) using
the frequency response of the BRDF filter.
I will demonstrate applications in two areas. First, we show how our
framework can be used for computing and displaying synthetic images in
real-time with natural illumination and physically-based BRDFs. We
will call this the "forward rendering" or the convolution problem. Next,
we extend and apply our framework to estimating realistic lighting and
reflective properties from photographs, and show how this
approach can be used to synthesize very realistic images under novel
lighting and viewing conditions. We will call this the "inverse
rendering" or the deconvolution problem. In my talk, I will first describe the
theoretical framework, and then discuss the above two applications.