Figure 1: Varv Examples: (a) A todo list web application that is inherently extensible. Here, a basic todo list is extended with the ability to complete and delete todos by adding two new concept defnitions and new modifed template defnitions. (b) A board game toolkit that defnes abstractions for board game logic. The games "Checkers" and "Othello" were implemented with the toolkit and then merged into a new "Checkers-O-Thello" game with the addition of a short concept defnition. As Varv applications are represented as data structures, higher-level tooling can be developed including a block-based editor (right), an inspector to go from an element in the view to the corresponding template or data (context menu to the left), and a data inspector for live editing application state (middle).
This paper proposes a series of techniques for improving the precision of optical fiducial tracking on tangible tabletops. The motivation is to enable convincing interactive projection mapping on tangibles on the table, which requires a high precision tracking of the location of tangibles. We propose a new fiducial design optimized for GPU based tracking, a technique for calibrating light that allows for computation on a greyscale image rather than a binarized black and white image, an automated technique for compensating for optical distortions in the camera lenses, and a tracking algorithm implemented primarily in shaders on the GPU. The techniques are realized in the BullsEye computer vision software. We demonstrate experimentally that BullsEye provides sub-pixel accuracy down to a tenth of a pixel, which is a significant improvement compared to the commonly used reacTIVision software.
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