Tomer Moscovich

As-rigid-as-possible shape manipulation

We present an interactive system that lets a user move and deform a two-dimensional shape without manually establishing a skeleton or freeform deformation (FFD) domain beforehand. The shape is represented by a triangle mesh and the user moves several vertices of the mesh as constrained handles. The system then computes the positions of the remaining free vertices by minimizing the distortion of each triangle. While physically based simulation or iterative refinement can also be used for this purpose, they tend to be slow. We present a two-step closed-form algorithm that achieves real-time interaction. The first step finds an appropriate rotation for each triangle and the second step adjusts its scale. The key idea is to use quadratic error metrics so that each minimization problem becomes a system of linear equations. After solving the simultaneous equations at the beginning of interaction, we can quickly find the positions of free vertices during interactive manipulation. Our approach successfully conveys a sense of rigidity of the shape, which is difficult in space-warp approaches. With a multiple-point input device, even beginners can easily move, rotate, and deform shapes at will.

CavePainting: a fully immersive 3D artistic medium and interactive experience

CavePainting is an artistic medium that uses a 3D analog of 2D brush strokes to create 3D works of art in a fully immersive Cave environment. Physical props and gestures are used to provide an intuitive interface for artists who may not be familiar with virtual reality. The system is designed to take advantage of the 8 ft. x 8 ft. x 8 ft. space in which the artist works. CavePainting enables the artist to create a new type of art and provides a novel approach to viewing this art after it has been created. In this paper, we describe CavePainting’s 3D brush strokes, color pickers, artwork viewing mode, and interface. We also present several works of art created using the system along with feedback from artists. Artists are excited about this form of art and the gestural, full-body experience of creating it. CR Categories and Subject Descriptors: I.3.6 [Computer Graphics]: Methodology and Techniques - Interaction Techniques; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism Virtual Reality; J.5 [Arts and Humanities]: Fine Arts Additional Key Words: 3D painting, 3D modeling, gestures, tangible user interface, Cave

Indirect mappings of multi-touch input using one and two hands

Touchpad and touchscreen interaction using multiple fingers is emerging as a valuable form of high-degree-of-freedom input. While bimanual interaction has been extensively studied, touchpad interaction using multiple fingers of the same hand is not yet well understood. We describe two experiments on user perception and control of multi-touch interaction using one and two hands. The first experiment addresses how to maintain perceptual-motor compatibility in multi-touch interaction, while the second measures the separability of control of degrees-of-freedom in the hands and fingers. Results indicate that two-touch interaction using two hands is compatible with control of two points, while twotouch interaction using one hand is compatible with control of a position, orientation, and hand-span. A slight advantage is found for two hands in separating the control of two positions.

Spatial keyframing for performance-driven animation

This paper introduces spatial keyframing, a technique for performance-driven character animation. In traditional temporal keyframing, key poses are defined at specific points in time: i.e., we define a map from a set key times to the configuration space of the character and then extend this map to the entire timeline by interpolation. By contrast, in spatial keyframing key poses are defined at specific key positions in a 3D space where the character lives; the mapping from the 3D space to the configuration space is again defined by interpolation. The user controls a character by adjusting the position of a control cursor in the 3D space; the pose of the character is given as a blend of nearby key poses. The user thus can make expressive motion in real time and the resulting motion can be recorded and interpreted as an animation sequence. Although similar ideas are present in previous systems, our system is unique in that the designer can quickly design a new set of keyframes from scratch, and make an animation without motion capture data or special input devices. Our technique is especially useful for imaginary characters other than human figures because we do not rely on motion-capture data. We also introduce several applications of the basic idea and give examples showing the expressiveness of the approach.

Contact area interaction with sliding widgets

We show how to design touchscreen widgets that respond to a fingers contact area. In standard touchscreen systems a finger often appears to touch several screen objects, but the system responds as though only a single pixel is touched. In contact area interaction all objects under the finger respond to the touch. Users activate control widgets by sliding a movable element, as though flipping a switch. These Sliding Widgets resolve selection ambiguity and provide designers with a rich vocabulary of self-disclosing interaction mechanism. We showcase the design of several types of Sliding Widgets, and report study results showing that the simplest of these widgets, the Sliding Button, performs on-par with medium-sized pushbuttons and offers greater accuracy for small-sized buttons.

Navigating documents with the virtual scroll ring

We present a technique for scrolling through documents that is simple to implement and requires no special hardware. This is accomplished by simulating a hardware scroll ring--a device that maps circular finger motion into vertical scrolling. The technique performs at least as well as a mouse wheel for medium and long distances, and is preferred by users. It can be particularly useful in portable devices where screen-space and space for peripherals is at a premium.

Reading comprehension programs in a statistical-language-processing class

We present some new results for the reading comprehension task described in [3] that improve on the best published results - from 36% in [3] to 41% (the best of the systems described herein). We discuss a variety of techniques that tend to give small improvements, ranging from the fairly simple (give verbs more weight in answer selection) to the fairly complex (use specific techniques for answering specific kinds of questions).

Interactive layered character animation in immersive virtual environments

We present a novel method for creating 3D animations by letting users act directly on 3D characters in a virtual reality Cave [CruzNeira et al. 1993] environment. Our system records the performance of the animator as she manipulates the character’s joints and limbs using 3D trackers. By making multiple passes, animators can layer simple motions to create more complex animations. For example, an animator may first record a character’s arm motion, and later the movement of its head. We believe our approach bridges the gap between animators and the characters they bring to life by making animators an integral part of the virtual world inhabited by their characters.