Section: New Results

Micro-dynamics

Participants : Géry Casiez [contact person] , Sylvain Malacria, Mathieu Nancel, Thomas Pietrzak.

Latency & Transfer functions

End-to-end latency in interactive systems is detrimental to performance and usability, and comes from a combination of hardware and software delays. While these delays are steadily addressed by hardware and software improvements, it is at a decelerating pace. In parallel, short-term input prediction has recently shown promising results to compensate for latency, in both research and industry.

In the context of the collaborative TurboTouch project, we proposed a method based on a frequency-domain approximation of a non-causal ideal predictor with a finite impulse response filter. Given a sufficiently rich dataset, the parameters of the filter can be either optimized off-line or tuned on-line with the proposed adaptive algorithm. The performance of the proposed solution is evaluated in an experimental study consisting of drawings on a touchscreen [13].

On the related topic of transfer functions, we proposed a switched dynamic model to model indirect pointing tasks with a computer mouse. The model contains a ballistic movement phase governed by a nonlinear model in Lurie form and a corrective movement phase described by a linear visual-feedback system. The stability of the model was evaluated and the derived model was then validated with experimental data acquired in a pointing task with a mouse. Numerical comparison to pointing models available in the literature is also provided [12].

3D interaction

Raycasting is the most common target pointing technique in virtual reality environments. However, performance on small and distant targets is impacted by the accuracy of the pointing device and the user's motor skills. Current pointing facilitation techniques are currently only applied in the context of the virtual hand, i.e. for targets within reach. We proposed enhancements to Raycasting: filtering the ray, and adding a controllable cursor on the ray to select the nearest target (Figure 2). We ran a series of studies for the design of the visual feedforward, filtering technique, as well as a comparative study between different 3D pointing techniques. Our results show that highlighting the nearest target is one of the most efficient visual feedforward technique. We also show that filtering the ray reduces error rate in a drastic way. Finally we show the benefits of RayCursor compared to Raycasting and another technique from the literature [19], [14].