Non-linear perspectives have the potential to improve 3D scene perception by increasing the information bandwidth of 3D contents. As with the example of the Mercator projection of earth, they can reduce occlusions by showing more of the shape of an object than classical perspectives. However, an ill-advised construction of such “usually static” perspectives could make the original shape difficult to understand, drastically reducing the scene comprehension. Yet, despite of their potential, these perspectives are rarely used. In this paper we aim at making non-linear perspectives more widely usable on mobile devices. We propose to solve the understanding issue by allowing the user to control the transition between linear and non-linear perspectives in real-time with bending gestures. Using this approach, we present the first user study that investigates real-time manipulation of non-linear perspectives in an exploration task. Results show significant benefits of the approach, and give insights on the best bending gestures and configurations.

In this paper, we present BEXHI, a new mechanical structure for prototyping expandable and bendable handheld devices. Many research projects have pushed bendable surfaces from prototypes to commercially viable devices. In the meantime, expandable devices have become a topic of interest letting one foresee that such devices are on the horizon. With BEXHI, we provide a structure to explore the combined capabilities of these devices. The structure consists of multiple interweaved units allowing non-porous expandable surfaces to bend. Through an instanciation, we illustrate and discuss that the BEXHI structure allows for the exploration of the combination of both bend and expansion interaction spaces.

This paper presents two new pointing techniques for wiggle 3D displays, which present the 2D projection of 3D content with automatic (rotatory) motion parallax. Standard pointing at targets in wiggle 3D displays is challenging as the content is constantly in motion. The two pointing techniques presented here take advantage of the cursor's current position or the user's gaze direction for collocating the wiggle rotation center and potential targets. We evaluate the performance of the pointing techniques with a novel methodology that integrates 3D distractors into the ISO-9241-9 standard task. The experimental results indicate that the new techniques are significantly more efficient than standard pointing techniques in wiggle 3D displays. Given that we observed no performance variation for different targets, our new techniques seem to negate any interaction performance penalties of wiggle 3D displays.

We present EXHI-bit, a mechanical structure for prototyping unique shape-changing interfaces that can be easily built in a fabrication laboratory. EXHI-bit surfaces consist of inter-weaving units that slide in two dimensions. This assembly enables the creation of unique expandable handheld surfaces with continuous transitions while maintaining the surface flat, rigid, and non-porous. EXHI-bit surfaces can be combined to create 2D and 3D multi-surface objects. In this paper, we demonstrate the versatility and generality of EXHI-bit with user-deformed and self-actuated 1D, 2D, and 3D prototypes employed in an architectural urban planning scenario. We also present vision on the use of expandable tablets in our everyday life from 10 users after having interacted with an EXHI-bit tablet.

This paper presents DOP8: a Data Mining Iterative Cycle that improves the classical data life cycle. While the latter only combines the data production and data analysis phases, DOP8 also integrates the analysis operators life cycle. In this cycle, data life cycle and operators life cycle processing meet in the data analysis step. This paper also presents a reification of DOP8 in a new computing platform: UnderTracks. The latter provides a flexibility on storing and sharing data, operators and analysis processes. Undertracks is compared with three types of platform 'Storage platform', 'Analysis platform' and 'Storage and Analysis platform'. Several real TEL analysis scenarios are present into the platform, (1) to test Undertracks flexibility on storing data and operators and (2) to test Undertracks flexibility on designing analysis processes.

In this paper we describe a new orbiting algorithm, called SHOCam, which enables simple, safe and visually attractive control of a camera moving around 3D objects. Compared with existing methods, SHOCam provides a more consistent mapping between the user's interaction and the path of the camera by substantially reducing variability in both camera motion and look direction. Also, we present a new orbiting method that prevents the camera from penetrating object(s), making the visual feedback -- and with it the user experience -- more pleasing and also less error prone. Finally, we present new solutions for orbiting around multiple objects and multi-scale environments.

Now that 3D interaction is available on tablets and smart phones, it becomes critical to provide efficient 3D interaction techniques for novice users. This paper investigates interaction techniques for 3D rotation with two fingers of a single hand, on multitouch mobile devices.

We present ACCD, an interaction technique that allows direct drawing of long curves on 3D shapes with a tablet display over both multiple depth layers and multiple viewpoints. ACCD reduces the number of explicit viewpoint manipulations by combining self-occlusion management and automated camera control. As such it enables drawing on occluded faces but also around a 3D shape while keeping a constant drawing precision. Our experimental results indicates the efficacy of ACCD over conventional techniques.

This paper presents IUCA (Interaction Using Camera Animations), a new interaction technique for 3D objects manipulation. IUCA allows efficient interaction in a full-resolution perspective view by integrating transients animated transitions to orthographic views into the manipulation task. This provides an interaction in context, with precise object positioning and alignment. An evaluation of the technique shows that, compared to the classical configurations, IUCA allows to reduce pointing time by 14% on average. Testing with professional 3D designers and novice users indicate that IUCA is easy to use and to learn; and that users feel comfortable with it.

Fitts' pointing paradigm is widely used to conduct controlled experiments and to evaluate new interaction techniques enhancing target acquisition. Many of them change the behavior of the cursor according to various inputs, most notably the positions of potential targets. We propose to extend Fitts' paradigm in order to challenge those techniques with distractors (i.e., potential targets which are not the goal of the user) in a controlled manner. To reduce variability, we add a single new factor to the paradigm, the distractor density. We specify a distractors distribution, fully determined by this factor together with those of Fitts' task, aimed at reducing bias toward a specific technique. We also propose a preliminary extension of Fitts' law to take account of the sensitivity to the density of distractors as well as of the task difficulty. In an experiment, we compare five existing pointing techniques, and show that this extended protocol enables contrasted comparisons between them.

We introduce and formalize a novel constrained path optimization problem that is the heart of the real-time ad serving task in the Yahoo! (formerly RightMedia) Display Advertising Exchange. In the Exchange, the ad server's task for each display opportunity is to compute, with low latency, an optimal valid path through a directed graph representing the business arrangements between the hundreds of thousands of business entities that are participating in the Exchange. These entities include not only publishers and advertisers, but also intermediate entities called "ad networks" which have delegated their ad serving responsibilities to the Exchange. Path optimality is determined by the payment to the publisher, and is affected by an advertiser's bid and also by the revenue-sharing agreements between the entities in the chosen path leading back to the publisher. Path validity is determined by constraints which focus on the following three issues: 1) suitability of the opportunity's web page and its publisher 2)suitability of the user who is currently viewing that web page, and 3) suitability of a candidate ad and its advertiser. Because the Exchange's constrained path optimization task is novel, there are no published algorithms for it. This paper describes two different algorithms that have both been successfully used in the actual Yahoo! ad server. The first algorithm has the advantage of being extremely simple, while the second is more robust thanks to its polynomial worst-case running time. In both cases, meeting latency caps has required that the basic algorithms be improved by optimizations; we will describe a candidate ordering scheme and a pre-computation scheme that have both been effective in reducing latency in the real ad serving system that serves over ten billion ad calls per day.

We investigate the use of two concurrent input channels to perform a pointing task. The first channel is the traditional mouse input device whereas the second one is the gaze position. The rake cursor interaction technique combines a grid of cursors controlled by the mouse and the selection of the active cursor by the gaze. A controlled experiment shows that rake cursor pointing drastically outperforms mouse-only pointing and also significantly outperforms the state of the art of pointing techniques mixing gaze and mouse input. A theory explaining the improvement is proposed: the global difficulty of a task is split between those two channels, and the sub-tasks could partly be performed concurrently.

In this paper, we illustrate the OpenInterface Interaction Development Environment (OIDE) that addresses the design and development of multimodal interfaces. Multimodal interaction software development presents a particular challenge because of the ever increasing number of novel interaction devices and modalities that can used for a given interactive application. To demonstrate our graphical OIDE and its underlying approach, we present a multimodal slideshow implemented with our tool.

This paper describes a generalization of the god-object method for haptic interaction between rigid bodies. Our approach separates the computation of the motion of the six degree-of-freedom god-object from the computation of the force applied to the user. The motion of the god-object is computed using continuous collision detection and constraint-based quasi-statics, which enables high-quality haptic interaction between contacting rigid bodies. The force applied to the user is computed using a novel constraint-based quasi-static approach, which allows us to suppress force artifacts typically found in previous methods. The constraint-based force applied to the user, which handles any number of simultaneous contact points, is computed within a few microseconds, while the update of the configuration of the rigid god-object is performed within a few milliseconds for rigid bodies containing up to tens of thousands of triangles. Our approach has been successfully tested on complex benchmarks. Our results show that the separation into asynchronous processes allows us to satisfy the different update rates required by the haptic and visual displays. Force shading and textures can be added and enlarge the range of haptic perception of a virtual environment. This paper is an extension of [1].

This paper describes a generalization of the god-object method for haptic interaction between rigid bodies. Our approach separates the computation of the motion of the six degree-of-freedom god-object from the computation of the force applied to the user. The motion of the god-object is computed using continuous collision detection and constraint-based quasi-statics, which enables high-quality haptic interaction between contacting rigid bodies. The force applied to the user is computed using a novel constraint-based quasi-static approach, which allows us to suppress force artifacts typically found in previous methods. Our approach has been implemented on a 3.2 GHz Xeon bi-processor and has been successfully tested on complex benchmarks. Our results show that the separation into asynchronous processes allows us to satisfy the different update rates required by the haptic and the visual displays. The constraint-based force applied to the user, which handles any number of simultaneous contact points, is typically computed within a few microseconds, while the update of the configuration of the rigid god-object is performed within a few milliseconds for rigid bodies containing up to tens of thousands of triangles.

In many applications, users specify target values for certain attributes/features without requiring exact matches to these values in return. Instead, the result is typically a ranked list of "top k" objects that best match the specified feature values. User subjectivity is an important aspect of such queries, i.e., which objects are relevant to the user and which are not depends on the perception of the user. Due to the subjective nature of top-k queries, the answers returned by the system to an user query often do not satisfy the users need right away, either because the weights and the distance functions associated with the features do not accurately capture the users perception or because the specified target values do not fully capture her information need or both. In such cases, the user would like to refine the query and resubmit it in order to get back a better set of answers. While there has been a lot of research on query refinement models, there is no work that we are aware of on supporting refinement of top-k queries efficiently in a database system. Done naively, each "refined" query can be treated as a "starting" query and evaluated from scratch. We explore alternative approaches that significantly improve the cost of evaluating refined queries by exploiting the observation that the refined queries are not modified drastically from one iteration to another. Our experiments over a real-life multimedia data set show that the proposed techniques save more than 80 percent of the execution cost of refined queries over the naive approach and is more than an order of magnitude faster than a simple sequential scan.

Content-based image retrieval (CBIR) has become one of the most active research areas in the past few years. Many visual feature representations have been explored and many systems built. While these research efforts establish the basis of CBIR, the usefulness of the proposed approaches is limited. Specifically, these efforts have relatively ignored two distinct characteristics of CBIR systems: (1) the gap between high-level concepts and low-level features, and (2) the subjectivity of human perception of visual content. This paper proposes a relevance feedback based interactive retrieval approach, which effectively takes into account the above two characteristics in CBIR. During the retrieval process, the user's high-level query and perception subjectivity are captured by dynamically updated weights based on the user's feedback. The experimental results over more than 70000 images show that the proposed approach greatly reduces the user's effort of composing a query, and captures the user's information need more precisely.

To address the emerging needs of applications that require access to and retrieval of multimedia objects, we are developing the Multimedia Analysis and Retrieval System (MARS). In this paper, we concentrate on the retrieval subsystem of MARS and its support for content-based queries over image databases. Content-based retrieval techniques have been extensively studied for textual documents in the area of automatic information retrieval. This paper describes how these techniques can be adapted for ranked retrieval over image databases. Specifically, we discuss the ranking and retrieval algorithms developed in MARS based on the Boolean retrieval model and describe the results of our experiments that demonstrate the effectiveness of the developed model for image retrieval.

To address the emerging needs of applications that require access to and retrieval of multimedia objects, we are developing the Multimedia Analysis and Retrieval System (MARS) in our group at the University of Illinois [13].In this paper, we concentrate on the retrieval subsystem of MARS and its support for content-based queries over image databases.Content-based retrieval techniques have been extensively studied for textual documents in the area of automatic information retrieval [24, 21.This paper describes how these techniques can be adapted for ranked retried over image databases.Specifically, we discuss the ranking and retrieval algorithms developed in MARS based on the Boolean re-trievaI model and describe the results of our experiments that demonstrate the effectiveness of the developed model for image retrieval.