Our observations of landscape architecture students revealed a new phenomenon-interstices. Their bimanual interactions with a pen and touch surface involved various sustained hand gestures, interleaved between their regular commands. Positioning of the non-preferred hand indicates anticipated actions, including: sustained hovering near the surface; pulled back but still floating above the surface; and resting in their laps. We ran a second study with 14 landscape architect students which confirmed our observations, and uncovered a new interstice i.e. stabilizing the preferred hand while handwriting. We conclude with directions for future research and challenges for designers and researchers.

We introduce, LayerFish, a bimanual interaction technique for layering overlapping content in large 2D design spaces. Designers compose visual elements, often producing overlap and requiring layering in the z-dimension. A common approach in design tools is to provide a scene index, as an ordered list of layered elements. Scene indexes become difficult, in terms of physical effort and human cognition, to deal with when working with hundreds of elements. LayerFish renders an in-place scene index as a fisheye to reduce demands on effort and attention. Bimanual gestures support selection, scrolling, and manipulation. We evaluated layering task performance with LayerFish in comparison to a traditional scene index. Findings indicate that the fisheye reduces time to find an element and selection reduces layering time when elements do not heavily overlap.