Ricardo Jota

How fast is fast enough?: a study of the effects of latency in direct-touch pointing tasks

Although advances in touchscreen technology have provided us with more precise devices, touchscreens are still laden with latency issues. Common commercial devices present with latency up to 125ms. Although these levels have been shown to impact users perception of the responsiveness of the system [16], relatively little is known about the impact of latency on the performance of tasks common to direct-touch interfaces, such as direct physical manipulation. In this paper, we study the effect of latency of a direct-touch pointing device on dragging tasks. Our tests show that user performance decreases as latency increases. We also find that user performance is more severely affected by latency when targets are smaller or farther away. We present a detailed analysis of users coping mechanisms for latency, and present the results of a follow-up study demonstrating user perception of latency in the land-on phase of the dragging task.

How Much Faster is Fast Enough?: User Perception of Latency & Latency Improvements in Direct and Indirect Touch

This paper reports on two experiments designed to further our understanding of users perception of latency in touch- based systems. The first experiment extends previous efforts to measure latency perception by reporting on a unified study in which direct and indirect form-factors are compared for both tapping and dragging tasks. Our results show significant effects from both form-factor and task, and inform system designers as to what input latencies they should aim to achieve in a variety of system types. A follow-up experiment investigates peoples ability to perceive small improvements to latency in direct and indirect form-factors for tapping and dragging tasks. Our results provide guidance to system designers of the relative value of making improvements in latency that reduce but do not fully eliminate lag from their systems.

Snake Charmer: Physically Enabling Virtual Objects

Augmented and virtual reality have the potential of being indistinguishable from the real world. Holographic displays, including head mounted units, support this vision by creating rich stereoscopic scenes, with objects that appear to float in thin air - often within arms reach. However, one has but to reach out and grasp nothing but air to destroy the suspension of disbelief. Snake-charmer is an attempt to provide physical form to virtual objects by revisiting the concept of Robotic Graphics or Encountered-type Haptic interfaces with current commodity hardware. By means of a robotic arm, Snake-charmer brings physicality to a virtual scene and explores what it means to truly interact with an object. We go beyond texture and position simulation and explore what it means to have a physical presence inside a virtual scene. We demonstrate how to render surface characteristics beyond texture and position, including temperature; how to physically move objects; and how objects can physically interact with the users hand. We analyze our implementation, present the performance characteristics, and provide guidance for the construction of future physical renderers.

Zero-latency tapping: using hover information to predict touch locations and eliminate touchdown latency

A method of reducing the perceived latency of touch input by employing a model to predict touch events before the finger reaches the touch surface is proposed. A corpus of 3D finger movement data was collected, and used to develop a model capable of three granularities at different phases of movement: initial direction, final touch location, time of touchdown. The model is validated for target distances >= 25.5cm, and demonstrated to have a mean accuracy of 1.05cm 128ms before the user touches the screen. Preference study of different levels of latency reveals a strong preference for unperceived latency touchdown feedback. A form of soft feedback, as well as other uses for this prediction to improve performance, is proposed.

High rate, low-latency multi-touch sensing with simultaneous orthogonal multiplexing

We present Fast Multi-Touch (FMT), an extremely high frame rate and low-latency multi-touch sensor based on a novel projected capacitive architecture that employs simultaneous orthogonal signals. The sensor has a frame rate of 4000 Hz and a touch-to-data output latency of only 40 microseconds, providing unprecedented responsiveness. FMT is demonstrated with a high-speed DLP projector yielding a touch-to-light latency of 110 microseconds.

Hammer Time!: A Low-Cost, High Precision, High Accuracy Tool to Measure the Latency of Touchscreen Devices

We report on the Latency Hammer, a low-cost yet highaccuracy and high-precision automated tool that measures the interface latency of touchscreen devices. The Hammer directly measures latency by triggering a capacitive touch event on a device using an electrically actuated touch simulator, and a photo sensor to monitor the screen for a visual response. This allows us to measure the full end-toend latency of a touchscreen system exactly as it would be experienced by a user. The Hammer does not require human interaction to perform a measurement, enabling the acquisition of large datasets. We present the operating principles of the Hammer, and discuss its design and construction; full design documents are available online. We also present a series of tools and equipment that were built to assess and validate the performance of the Hammer, and demonstrate that it provides reliable latency measurements.

Let's kick it: how to stop wasting the bottom third of your large screen display

Large-scale touch surfaces have been widely studied in literature and adopted for public installations such as interactive billboards. However, current designs do not take into consideration that touching the interactive surface at different heights is not the same; for body-height displays, the bottom portion of the screen is within easier reach of the foot than the hand. We explore the design space of foot input on vertical surfaces, and propose three distinct interaction modalities: hand, foot tapping, and foot gesturing. Our design exploration pays particular attention to areas of the touch surface that were previously overlooked: out of hands reach and close to the floor. We instantiate our design space with a working prototype of an interactive surface, in which we are able to distinguish between finger and foot tapping and extend the input area beyond the bottom of the display to support foot gestures.

Collaborative Visualization of Sensor Data Through a Subscription based Architecture

AbstractIn this paper we propose a collaborative prototype for the integration of GIS sensor data into a distributed archi-tecture for Virtual Reality. Sensor data of various origin and classified domains are provided using a topic sub-scription metaphor. A graphical editor, which allows creation/import/export/manipulation of sensor data, servesas a real-time administrative interface to control the provision of topics/sensorial data and, at the same time, itis used as an interface to common GIS applications. A client application, responsible for the rendering, decidesaccording to the context which data (timevarying, static) is relevant for the actual examination. Additionally, ter-rain cultures like forests, buildings, streets along with their geometrical and semantical attributes are provided byusing queries to a Web Feature Service/PostGIS Database and translated to a 3D representation. These queriesare broadcasted to all clients in the framework to assure at all times synchronicity of the examination data. Fi-nally Session Management is enabled by storing the messages in a relational database to achieve persistency andrecalling of the analysis process.Categories and Subject Descriptors