Subscribe free to our newsletters via your
. 24/7 Space News .




TECH SPACE
Perfecting digital imaging
by Staff Writers
Cambridge MA (SPX) Jul 26, 2013


The subtleties in these computer-generated images of translucent materials are important. Texture, color, contrast, and sharpness combine to create a realistic image. (Courtesy of Ioannis Gkioulekas and Shuang Zhao.)

Computer graphics and digital video lag behind reality; despite advances, the best software and video cameras still cannot seem to get computer-generated images and digital film to look exactly the way our eyes expect them to.

But Hanspeter Pfister and Todd Zickler, computer science faculty at the Harvard School of Engineering and Applied Sciences (SEAS), are working to narrow the gap between 'virtual' and 'real' by asking a common question: how do we see what we see?

Between them, Pfister and Zickler are presenting three papers this week at SIGGRAPH 2013, the 40th International Conference and Exhibition on Computer Graphics and Interactive Techniques.

Realistic soap
One project led by Zickler, the William and Ami Kuan Danoff Professor of Electrical Engineering and Computer Science, tries to find better ways to mimic the appearance of a translucent object, such as a bar of soap. The paper elucidates how humans perceive and recognize real objects and how software can exploit the details of that process to make the most realistic computer-rendered images possible.

"If I put a block of butter and a block of cheese in front of you, and they're the same color, and you're looking for something to put on your bread, you know which is which," says Zickler. "The question is, how do you know that? What in the image is telling you something about the material?"

His hope is to eventually understand these properties well enough to instruct a computer with a camera to identify what material an object is made of and to know how to properly handle it-how much it weighs or how much pressure to safely apply to it-the way humans do.

The new approach focuses on translucent materials' phase function, part of a mathematical description of how light refracts or reflects inside an object, and, therefore, how we see what we see.

In the past, phase function shape was considered relevant to an object's translucent appearance, but formal perceptual studies had never been carried out. This is because the space of different phase functions is so vast and perceptually diverse to the human brain that modern computational tools were required to generate and analyze so many different images.

Zickler's team took advantage of increased computational power to trim down the potential space of images to a manageable size. They first rendered thousands of computer-generated images of one object with different computer-simulated phase functions, so each image's translucency was slightly different from the next. From there, a program compared each image's pixel colors and brightness to another image in the space and decided how different the two images were.

Through this process, the software created a map of the phase function space according to the relative differences of image pairs, making it easy for the researchers to identify a much smaller set of images and phase functions that were representative of the whole space.

Finally, the researchers asked people to compare these representative images and judge how similar or different they were, shedding light on the properties that help us decide which objects are plastic and which are soap simply by looking at them.

"This study, aiming to understand the appearance space of phase functions, is the tip of the iceberg for building computer vision systems that can recognize materials," says Zickler. The next step in this research will involve finding ways to accurately measure a material's phase functions instead of making them up computationally, and Zickler's team is already making progress on this, with a new system that will be presented at SIGGRAPH Asia in December.

Zickler's coauthors were Ioannis Gkioulekas, a graduate student at Harvard SEAS; Bei Xiao and Edward H. Adelson of MIT; and Shuang Zhao and Kavita Bala of Cornell University.

Adaptive displays
A second study involving Zickler investigates a new type of screen hardware that displays different images when lit or viewed from different directions.

By creating tiny grooves of varying depths across the screen's surface, Zickler's team created optical interference effects that cause the thin surface to look different when illuminated or viewed from different angles.

The paper essentially asks, "If I know what appearances I want the screen to have, how do I optimize the geometric structure to get that?" Zickler explains.

The solution takes advantage of mathematical functions (called bidirectional reflectance distribution functions) that represent how light coming from a particular direction will reflect off a surface.

Past attempts to control surface reflection for graphics applications have only been accomplished for surfaces displaying huge images that, for example, have pixels the size of a square inch, because their analyses did not account for interference effects. Zickler's work, however, demonstrates that interference effects can be exploited to control reflection from a screen at micron scales using well-known photolithographic techniques.

In the future, this kind of optimization could enable multi-view, lighting-sensitive displays, where a viewer rotating around a flat surface could perceive a three-dimensional object while looking at the surface from different angles, and where the virtual object would correctly respond to external lighting.

"Looking at such a display would be exactly like looking through a window," Zickler says.

He was joined on this paper by Ying Xiong, a graduate student at Harvard SEAS; Anat Levin and Daniel Glazner at the Weizmann Institute of Science; and Fredo Durand, William Freeman, and Wojciech Matusik at MIT.

Vivid color
A third paper, led by Hanspeter Pfister, An Wang Professor of Computer Science, tackled a problem in digital film editing. (Video: http://youtu.be/cYbDJ4NR6WY) Color grading-editing a video to impose a particular color palette-has historically been a painstaking, manual process requiring many hours' work by skilled artists. Amateur filmmakers therefore cannot achieve the characteristically rich color palettes of professional films.

"The starting idea was to appeal to broad audience, like the millions of people on YouTube," says lead author Nicolas Bonneel, a postdoctoral researcher in Pfister's group at SEAS.

Pfister's team hopes to make frame-by-frame editing unnecessary by creating software that lets users simply select, hypothetically, the Amelie look or the Transformers look. The computer would then apply that color palette to the user's video via a few representative frames. The user only has to indicate where the foreground and background are in each frame, and the software does the rest, interpolating the color transformations throughout the video.

Bonneel estimates that the team's new color grading method could be incorporated into commercially available editing software within the next few years.

Pfister and Bonneel were joined on this paper by Kalyan Sunkavalli and Sylvain Paris of Adobe Systems, Inc.

.


Related Links
Harvard School of Engineering and Applied Sciences
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








TECH SPACE
Controlling friction by tuning van der Waals forces
Saarbrucken, Germany (SPX) Jul 22, 2013
For a car to accelerate there has to be friction between the tire and the surface of the road. The amount of friction generated depends on numerous factors, including the minute intermolecular forces acting between the two surfaces in contact - so-called van der Waals forces. The importance of these intermolecular interactions in generating friction has long been known, but has now been de ... read more


TECH SPACE
Bad night's sleep? The moon could be to blame

Moon Base and Beyond

First-ever lunar south pole mission could be attempted by 2016

Engine recovered from Atlantic confirmed as Apollo 11 unit

TECH SPACE
Curiosity Mars Rover Gleams in View from Orbiter

Mars Curiosity sets one-day driving distance record

Scientists establish age of Mars meteorites found on Earth

Ancient snowfall likely carved Martian valleys

TECH SPACE
Dutch city patently the world's most inventive

NASA starts building faster-than-light warp engine

Zero Gravity Solutions Commences Trading Of Its Stock

Boeing CST-100 Spacecraft Model Passes Water-Recovery Tests

TECH SPACE
China launches three experimental satellites

Medical quarantine over for Shenzhou-10 astronauts

China's astronauts ready for longer missions

Chinese probe reaches record height in space travel

TECH SPACE
ISS Research Exposing the Salty Truth of Supercritical Water Transitions

NASA launches new probe of spacesuit failure

Space Station ARISS Software Upgraded by Student For Students

Astronaut's helmet leak forces abrupt end to spacewalk

TECH SPACE
Three Soyuz launchers are at the Spaceport for Arianespace's upcoming medium-lift missions from French Guiana

Flawless launch of Alphasat, Europe's largest and most sophisticated telecom satellite

Alphasat Wears Its Color For Alphabus

Both payloads for Arianespace's next Ariane 5 flight are now mated to the launcher

TECH SPACE
Solar system's youth gives clues to planet search

Snow falling around infant solar system

'Water-Trapped' Worlds

A snow line in an infant solar system: Astronomers take first images

TECH SPACE
Perfecting digital imaging

Ancient technology for metal coatings 2,000 years ago can't be matched even today

Controlling friction by tuning van der Waals forces

Carnegie Mellon, Microsoft researchers demonstrate internal tagging technique for 3D-printed objects




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement