Smartwatches offer powerful features, but their small touchscreens limit the expressiveness of the input that can be achieved. To address this issue, we present, and open-source, the first sonar-based around-device input on an unmodified consumer smartwatch. We achieve this using a fine-grained, one-dimensional sonar-based finger-tracking system. In addition, we use this system to investigate the fundamental issue of how to trigger selections during around-device smartwatch input through two studies. The first examines the methods of double-crossing, dwell, and finger tap in a binary task, while the second considers a subset of these designs in a multi-target task and in the presence and absence of haptic feedback. Results showed double-crossing was optimal for binary tasks, while dwell excelled in multi-target scenarios, and haptic feedback enhanced comfort but not performance. These findings offer design insights for future around-device smartwatch interfaces that can be directly deployed on today's consumer hardware.

Existing 3D face alignment primarily aim to achieve accurate face alignment result for a static facial image. While these methods have strong alignment performance under large poses, occlusion, and extreme lighting conditions, they often result in trembling artifacts in video-based sequential 3D face alignment. Reducing temporal misalignment remains a challenging task because a single misaligned frame can propagate errors to other frames along the temporal axis. To address this issue, we propose a novel temporal discriminating scheme that learns the distribution gap between the face alignment results and ground truth face animation. By leveraging the discrimination results as a guide, the proposed method can effectively align the 3D faces to the input video by reducing temporal trembling artifacts. To effectively learn the distribution gap, we introduce a multi-discriminating scheme that separately discriminates facial animation based on identity and expression changes. It enables the proposed method to produce a stabilized alignment result, especially in dynamic and fast movement. Through extensive experiments in both qualitative and quantitative evaluations, it is confirmed that our method outperforms state-of-the-art 3D face alignment methods by animating stabilized results in the video.