Due to the recent advances in technologies for gesture recognition, midair gestures can be considered the interface of the future in a large number of applications. However, designing effective interfaces with midair gestures is not an easy task because the design is application dependent and it must fulfill many requirements at the same time. Despite the availability of general guidelines in the literature, clear and well-established procedures for the optimal design of midair gesture-based interfaces are, to date, not available and remain an open issue. The main contribution of this paper is a user-centered modular framework, which integrates existing and novel methods. It supports the designer considering multiple aspects including ergonomics, memorability, and specific user requirements tailored to the application scenario. The framework involves three design steps and a final validation step, also supported by dedicated software. We tested with success the proposed framework in an industrial case study, where technicians must easily access technical information by browsing digital manuals during maintenance operations.

Text readability with augmented reality head-worn displays is critical and at present time, there are no standard guidelines to follow. The readability depends mainly on background lighting, display technology (i.e., OST: optical see-through or VST: video see-through), and text style (e.g., plain text, outline or billboard). In this work, we addressed the readability limits for industrial activities. We experimented the effects of two background illuminances levels (1,000 lx for very fine basic industrial tasks and 4,000 lx for fine machining), two commercially available head-worn display technologies, variable outline widths and contrast polarity of text. We analyzed the performance of 12 subjects by collecting about 3,400 measurements using a specific test application and followed by qualitative interviews. With high illuminances, VST performed better than OST, regardless of contrast polarity and outline width. We found that negative contrast polarity is preferable with VST, and that just a minimum outline (1 px) around black text is optimal. On the contrary, positive contrast polarity should be used with OST and outline is not effective. Therefore, we evaluated the usage limits of the OST by sampling its contrast sensitivity function.

Efficient text visualization in head-worn augmented reality (AR) displays is critical because it is sensitive to display technology, text style and color, ambient illumination and so on. The main problem for the developer is to know the optimal text style for the specific display and for applications where color coding must be strictly followed because it is regulated by laws or internal practices. In this work, we experimented the effects on readability of two head-worn devices (optical and video see-through), two backgrounds (light and dark), five colors (white, black, red, green, and blue), and two text styles (plain text and billboarded text). Font type and size were kept constant. We measured the performance of 15 subjects by collecting about 5,000 measurements using a specific test application and followed by qualitative interviews. Readability turned out to be quicker on the optical see-through device. For the video see-through device, background affects readability only in case of text without billboard. Finally, our tests suggest that a good combination for indoor augmented reality applications, regardless of device and background, could be white text and blue billboard, while a mandatory color should be displayed as billboard with a white text message.

We introduce the 3D warp brush, a method for interactive shape modeling in a immersive virtual reality environment. 3D warp brushes are implicitly-defined tools that operate on triangle meshes. We combine the efficiency of explicit mesh representations with implicit modeling operators. The area of influence of a 3D warp brush can be of arbitrary shape since it has an associated distance field. We define different warp functions including drag, explode, and whittle. A unique feature of our framework is the ability to convert meshes into 3D warp brushes at run time. The use of a Responsive Workbench and two-handed interaction allows the user to exploit the full potential of the modeling system by intuitive and easy modification of a base surface into a desired shape. We present models, which have been created and modified using 3D warp brushes, to demonstrate the usefulness of our framework.

Spacedesign is an innovative mixed reality (MR) application addressed to aesthetic design of free form curves and surfaces. It is a unique and comprehensive approach which uses task-specific configurations to support the design workflow from concept to mock-up evaluation and review. The first-phase conceptual design benefits from a workbench-like 3-D display for free hand sketching, surfacing and engineering visualization. Semitransparent stereo glasses augment the pre-production physical prototype by additional shapes, textures and annotations. Both workspaces share a common interface and allow collaboration and cooperation between different experts, who can configure the system for the specific task. A faster design workflow and CAD data consistency can be thus naturally achieved. Tests and collaborations with designers, mainly from automotive industry, are providing systematic feedback for this ongoing research. As far as the authors are concerned, there is no known similar approach that integrates the creation and editing phase of 3D curves and surfaces in virtual and augmented reality (VR/AR). Herein we see the major contribution of our new application.

We present a new technique for surface reconstruction of digitized models in three dimensions. Concerning this problem, we are given a data set in three-dimensional space, represented as a set of points without connectivity information, and the goal is to find, for a fixed number of vertices, a set of approximating triangles which minimize the error measured by the displacement from the given points. Our method creates near-optimal linear spline approximations, using an iterative optimization scheme based on simulated annealing. The algorithm adopts the mesh to the data set and moves the triangles to enhance feature lines. At the end, we can use the approach to create a hierarchy of different resolutions for the model.