Seeing is Believing
Lecturers: Alan Chalmers,
Ann McNamara, Scott Daly, Holly Rushmeier, et al.
By Anders Frick
12 August 2001
How do we know
if the image is real?
from the university of Bristol introduced the course "Seeing is
Believing" in a quite dramatic way. He also gave a little background
to the Sunday afternoon course in the West Hall A at the SIGGRAPH
One of the main
goals is to increase the realism and decrease the rendering time.
Chalmers tells us that even if it is possible to allow very precise
simulation of light-energy distribution in a scene, that doesn't
ensure that the final image will have a high fidelity visual appearance.
speaker, Ann McNamara from Trinity College in Dublin, Ireland, told
the audience about how to determine the relationship between the
physical world and how man understands that world. She also presented
some important things to think about when you are going carry out
It is very important
to think about the order effects. For example, if you always show
an ugly picture before a nice picture, or always a dark image after
a white one, there will surely be order effects that may affect
the final test results. You must randomize in the "right way", she
computer graphics and has been to the SIGGRAPH conference four times.
She is a scientist but very interested in psychology and that was
why she was speaking about psychophysical image quality metrics
Further on, Scott
Daly from Sharp Laboratories was talking. Daly is leader at the
center of excellence for displayed appearance and also a key member
of the technical staff at the digital video department at Sharp
Labs. He talked about computational image quality metrics, which
included everything from how the eye works to comparing different
models such as the Visible Differences Predictor, VDP, and the Sarnoff
Daly told the audience about the fact that human being is less sensitive
to lines that have a 45-degree angle, and that knowledge has been
used by the halftoning industry for long time. He also said that
smooth tracking eye movements can reduce image velocity on the retina,
and showed some examples on the big screen how people can perceive
things, depending on many different factors.
have simply different thresholds for what they can see and be aware
Seeing is believing
and at last Holly Rushmeier from the IBM T.J. Watson Research Center
talked about metrics and geometric simplifications. Image fidelity
depends on reflectance, transmittance and emission from the image.
She spoke about the limit for replacing geometry with just good
texture. Texture detail can distract from simplified geometry and
the knowledge how to find that limit between texture quality and
geometry simplification is very valuable.