Compact Totally Disconnected Moufang Buildings

Let $\Delta$ be a spherical building each of whose irreducible components is infinite, has rank at least 2 and satisfies the Moufang condition. We show that $\Delta$ can be given the structure of a topological building that is compact and totally disconnected precisely when $\Delta$ is the building at infinity of a locally finite affine building.Comment: To appear in Tohoku Math. Journa

A LED-Based IR/RGB End-to-End Latency Measurement Device

Achieving a minimal latency within augmented reality (AR) systems is one of the most important factors to achieve a convincing visual impression. It is even more crucial for non-video augmentations such as dynamic projection mappings because in that case the superimposed imagery has to exactly match the dynamic real surface, which obviously cannot be directly influenced or delayed in its movement. In those cases, the inevitable latency is usually compensated for using prediction and extrapolation operations, which require accurate information about the occurring overall latency to exactly predict to the right time frame for the augmentation. Different strategies have been applied to accurately compute this latency. Since some of these AR systems operate within different spectral bands for input and output, it is not possible to apply latency measurement methods encoding time stamps directly into the presented output images as these might not be sensed by used input device.We present a generic latency measurement device which can be used to accurately measure the overall end-to-end latency of camera-based AR systems with an accuracy below one millisecond. It comprises a LED-based time stamp generator displaying the time as a gray code on spatially and spectrally multiple locations. It is controlled by a micro-controller and sensed by an external camera device observing the output display as well as the LED device at the same time

Magic Prints: Image-Changing Prints Observed under Visible and 365 nm UV Light

In this paper we propose a novel layered-printing method consisting of superposed visible cmy and invisible fluorescent ultraviolet (UV) rgb inks. Our approach can be used to generate a variety of visual color-alteration effects such as revealing two completely distinct images when the print is illuminated with either standard visible or 365 nm ultraviolet (UV) light (Figure 1). This is achieved by computing the maximum achievable color gamuts for both illumination conditions, generating accurate estimates, and applying a spatial-varying gamut mapping to minimize potential ghosting artifacts and calculate the optimal ink surface coverages that, when printed, generate the desired image-alteration effect. Our method uses invisible UV-rgb fluorescent inks which are printed onto a transparent film. It is placed on top of a visible print consisting of standard cmy inks. By separating the UV and the visible inks using the transparent film, physical mixing of the two different ink types is avoided. This significantly increases the intensity of the fluorescent emission resulting in stronger and more vivid color-alteration effects. Besides the revealing of two different images, the same method can be applied for other use cases as well, such as enhancing or adding specific parts to an image under one illumination condition, generating personalized document security features, or aiding color-blind people in color distinction. (C) 2019 Society for Imaging Science and Technology

Spatial Augmented Reality for Architecture Designing and planning with and within existing buildings

At present, more than half of all building activity in the German building sector is undertaken within existing built contexts. The development of a conceptual and technological basis for the digital support of design directly on site, within an existing building context is the focus of the research project “Spatial Augmented Reality for Architecture” (SAR). This paper describes the goals achieved in one aspect of the project: the sampling of colors and materials at a scale of 1:1 using Augmented Reality (AR) technologies. We present initial results from the project, the development of an ad-hoc visualization of interactive data on arbitrary surfaces in real-world indoor environments using a mobile hardware setup. With this, it was possible to project the color and material qualities of a design directly onto almost all surfaces within a geometrically corrected, existing building. Initially, a software prototype “Spatial Augmented Reality for Architecture-Colored Architecture” (SAR-CA) was developed and then assessed based on evaluation results from a user study