Browsing by Author "Jorge, Joaquim A."

Now showing 1 - 3 of 3
  • No Thumbnail Available
    ItemMetadata only
    A comparison of ray pointing techniques for very large displays
    (Canadian Information Processing Society, 2010) Jota, Ricardo; Nacenta, Miguel A.; Jorge, Joaquim A.; Carpendale, Sheelagh; Greenberg, Saul
    Ray-pointing techniques are often advocated as a way for people to interact with very large displays from several meters away. We are interested in two factors that can affect ray pointing: the particular technique's control type, and parallax. Consequently, we tested four ray pointing variants on a wall display that covers a large part of the user's field of view. Tasks included horizontal and vertical targeting, and tracing. Our results show that (a) techniques based on 'rotational control' perform better for targeting tasks, and (b) techniques with low parallax are best for tracing tasks. We also show that a Fitts's law analysis based on angles (as opposed to linear distances) better approximates people's ray pointing performance.
  • Thumbnail Image
    ItemOpen Access
    The Continuous Interaction Space: Integrating Gestures Above a Surface with Direct Touch
    (2009-04-29T19:57:06Z) Marquardt, Nicolai; Jota, Ricardo; Greenberg, Saul; Jorge, Joaquim A.
    The advent of touch-sensitive and camera-based digital surfaces has spawned considerable development in two types of hand-based interaction techniques. In particular, people can interact: 1) directly on the surface via direct touch, or 2) above the surface via hand motions. While both types have value on their own, we believe much more potent interactions are achievable by unifying interaction techniques across this space. That is, the underlying system should treat this space as a continuum, where a person can naturally move from gestures over the surface to touches directly on it and back again. We illustrate by example, where we unify actions such as selecting, grabbing, moving, reaching, and lifting across this continuum of space.
  • Thumbnail Image
    ItemOpen Access
    Non-Photorealistic Rendering in Context: An Observational Study
    (2006-02-14) Isenberg, Tobias; Neumann, Petra; Carpendale, Sheelagh; Costa Sousa, Mario; Jorge, Joaquim A.
    Pen-and-ink line drawing techniques are frequently used to depict form, tone, and texture in artistic, technical, and scientific illustration. In non-photorealistic rendering (NPR), there has been considerable progress on reproducing traditional pen-and-ink techniques for rendering 3D objects. However, formal evaluation and validation of these NPR images remain an important open research problem. In this paper we present an observational study with three groups of users to examine their understanding and assessment of hand-drawn pen-and-ink illustrations of objects in comparison with NPR renditions of the same 3D objects. The results show that people perceive differences between those two types of illustration but that those that look computer-generated are still highly valued in terms of scientific illustration.