Prabath Gunawardane

Synthetic Shutter Speed Imaging

Hand held long exposures often result in blurred photographs due to camera shake. Long exposures are desirable both for artistic effect and in low‐light situations. We propose a novel method for digitally reducing imaging artifacts, which does not require additional hardware such as tripods or optical image stabilization lenses. A series of photographs is acquired with short shutter times, stabilized using image alignment, and then composited. Our method is capable of reducing noise and blurring due to camera shake, while simultaneously preserving the desirable effects of motion blur. The resulting images are very similar to those obtained using a tripod and a true extended exposure.

Material classification using BRDF slices

Segmenting images into distinct material types is a very useful capability. Most work in image segmentation addresses the case where only a single image is available. Some methods improve on this by collecting HDR or multispectral images. However, it is also possible to use the reflectance properties of the materials to obtain better results. By acquiring many images of an object under different lighting conditions we have more samples of the surfaces bidirectional reflectance distribution function (BRDF). We show that this additional information enlarges the class of material types that can be well separated by segmentation, and that properly treating the information as samples of the BRDF further increases accuracy without requiring an explicit estimation of the material BRDF.

Image-Based Empirical Information Acquisition, Scientific Reliability, and Long-Term Digital Preservation for the Natural Sciences and Cultural Heritage

The tools and standards of best practice adopted by natural science (NS) and cultural heritage (CH) professionals will determine the digital future of NS and CH digital imaging work. This tutorial discusses emerging digital technologies and explores issues influencing widespread adoption of digital practices for NS and CH. The tutorial explores a possible digital future for NS and CH through key concepts; adoption of digital surrogates, empirical (scientific) provenance, perpetual digital conservation, and ‘born archival’ semantic knowledge management. The tutorial discusses multiple image based technologies along with current research including; Reflectance Transformation Imaging (RTI), Photometric Stereo, and new research in the next generation of multi-view RTI. This research involves extending stereo correspondence methods. These technologies permit generation of digital surrogates that can serve as trusted representations of ‘real world’ content. The tutorial explores how empirical provenance contributes to the reliability of digital surrogates, and how perpetual digital conservation can ensure that digital surrogates will be archived and available for future generations. The tutorial investigates the role of semantically based knowledge management strategies and their use in simplifying ease of use by natural science and CH professionals as well as long term preservation activities. The tutorial also investigates these emerging technologies’ potential to democratize digital technology, making digital tools and methods easy to adopt and make NS and CH materials widely available to diverse audiences. The tutorial concludes with handson demonstrations of image-based capture and processing methods and a practical problem solving Q&A with the audience.

3D+2DTV: 3D displays with no ghosting for viewers without glasses

3D displays are increasingly popular in consumer and commercial applications. Many such displays show 3D images to viewers wearing special glasses, while showing an incomprehensible double image to viewers without glasses. We demonstrate a simple method that provides those with glasses a 3D experience, while viewers without glasses see a 2D image without artifacts. In addition to separate left and right images in each frame, we add a third image, invisible to those with glasses. In the combined view seen by those without glasses, this cancels the right image, leaving only the left. If the left and right images are of equal brightness, this approach results in low contrast for viewers without glasses. Allowing differential brightness between the left and right images improves 2D contrast. We observe experimentally that: (1) viewers without glasses prefer our 3D+2DTV to a standard 3DTV, (2) viewers with glasses maintain a strong 3D percept, even when one eye is significantly darker than the other, and (3) sequential-stereo display viewers with glasses experience a depth illusion caused by the Pulfrich effect, but it is small and innocuous. Our technique is applicable to displays using either active shutter glasses or passive glasses. Our prototype uses active shutter glasses and a polarizer.

Motion capture data retrieval using an artist’s doll

In this paper, we present a keyframe-based human motion capture data retrieval system which uses a wooden doll as the input device. A user inputs a keyframe by posing an artistpsilas doll with painted joints in front of a stereo camera rig. The system interactively gives real-time feedback on the results of the joint detection and 3D pose reconstruction as the user is positioning and rotating the doll. The robust 3D joint reconstruction is achieved by integrating 3D joint positions from multiple views of the same pose. After the user has finished inputting all the keyframes, the motion sequences are retrieved from the database and ranked based on their similarities to the keyframes. Experiments show that the presented system is simple to use and has high quality of retrieval results.

Optimized image sampling for view and light interpolation

Accurate virtual reconstruction of real world objects has long been a desired goal of image-based computer graphics. Usually this involves a lengthy capture process where an object is photographed from different viewpoints and illumination conditions. Using this collection of input images, we can now re-render the object from any viewing angle or lighting condition. However, acquiring a dense sampling of both the lighting and view space is time consuming. We carry out an analysis on this combined lighting and view space to find the optimal sampling given a restricted image budget. We also analyze the order of interpolation and find that improved results are obtained by interpolating first in viewpoint and second in lighting, the reverse of the usual order.

Invisible light: Using infrared for video conference relighting

Desktop video conferencing often suffers from bad lighting, which may be caused by harsh shadowing, saturated regions, etc. The primary reason for this is the lack of control over lighting in the users environment. A hardware-based solution to this problem would be to place lights near the video camera, but these would be distracting to the user. We use a set of infrared lights placed around the computer monitor to gather a sequence of frames which is used to infer surface normals of the scene. These are used in combination with a visible spectrum image to create an improved relighting result.

Same frame rate IR to enhance visible video conference lighting

Professional studios produce good lighting by using well-positioned, bright studio lights to illuminate the subjects, while casual desktop video conferencing often suffers from uneven and unreliable lighting. Using bright lights is not an option — they annoy and distract non-professional subjects. In this work, we illuminate the subjects using invisible near infrared (IR) lights and capture the subject simultaneously in IR and visible light. The IR video is used as a reference to enhance the visible video. The advantages of IR illumination for video conferencing have previously been shown, but the prior works require 4 to 8 times higher IR frame rate, with concomitant complexity and bandwidth increases. The enhancement developed here performs well with low IR frame rates equal to the visible frame rate. The technique works well even when uneven lighting causes bright visible light pixels to clip. After describing the technique, comparisons with prior methods are provided.

Analyzing statistical relationships between global indicators through visualization

There is a wealth of information collected about national level socio-economic indicators across all countries each year. These indicators are important in recognizing the level of development in certain aspects of a particular country, and are also essential in international policy making. However with past data spanning several decades and many hundreds of indicators evaluated, trying to get an intuitive sense of this data has in a way become more difficult. This is because simple indicator-wise visualization of data such as line/bar graphs or scatter plots does not do a very good job of analyzing the underlying associations or behavior. Therefore most of the socio-economic analysis regarding development tends to be focused on few main economic indicators. However, we believe that there are valuable insights to be gained from understanding how the multitude of social, economic, educational and health indicators relate to each other.

Keyframe animation using an artist's doll

Keyframe animation of an articulated human figure is a difficult task due to the large number of degrees of freedom inherent in the models 3D joints, the complex range of motion and the vast amount of possible interpolations between keyframes. Existing software solutions, such as Maya and Poser, try to solve these problems by providing extensive user control over positioning and orientation of joints, etc. However, due to the sheer number of adjustable parameters and settings in these interfaces, skills of a master animator are required to create satisfactory results.