An image printed on reflectance paper responds to the direction from which it is illuminated. The reflectance paper is covered with dimples that reflect light from different directions. |
A novel printing
method yields photos that respond to different angles of light the same way a 3D
object does. The technique, which uses specially designed “reflectance
paper” covered with thousands of tiny dimples, was developed by a team of
researchers at the University of California, Santa Cruz; Hewlett-Packard
Laboratories; and 3M.
James Davis, an
associate professor of computer science in the Baskin School of Engineering at
UC Santa Cruz, explained that ordinary printed photos look the same regardless
of the angle of the light because flat paper can’t reflect light the way 3D
objects do.
“If the
paper is flat, it will always look flat no matter what you print on it. So the
question became how to get the surface of the paper to have geometry to
it,” Davis says. “With the reflectance paper, for each pixel we have
a little dimple that has all angular directions on its surface. Now we can
print ink over it in a way that controls the angles of light that will be
reflected from each pixel.”
The mathematical
“reflectance function” describes how light is reflected from each point
on an object. Measuring the reflectance functions for an object or scene can be
done by taking photographs lit from many different lighting directions. Art
historians and restorers use these techniques for documenting important works
of art and historical artifacts, says Davis, a computer graphics expert who has
developed software for displaying the results on a monitor.
“Right now
the quality of our prints is nowhere near what museums would need, but the
basic idea of being able to capture all of that information in a print is
absolutely of interest to them,” Davis says. “It’s not just a
novelty. There are potential uses where people would want to take a picture and
examine it later from different lighting angles.”
The idea for the
project emerged from a graduate course Davis was teaching, but he says it
wouldn’t have gone anywhere if he hadn’t brought the idea to the HP researchers
he was collaborating with on another project. “This is a great example of
industry-university collaboration. We had the idea, but we didn’t know how to
make it work,” Davis says.
The researchers
at HP Laboratories, Tom Malzbender and Ramin Samadani, eventually teamed up
with Douglas Dunn at 3M to develop the reflectance paper. At UCSC, Davis worked
with two computer science graduate students, Steven Scher and Adam Crume, to
write the software code for printing the reflectance functions. The team has
published their results in a paper in ACM Transactions on Graphics.
