The quality of every dynamic multi-projection mapping system is limited by the quality of the projector to tracking device calibration. Common problems with poor calibration result in noticeable artifacts for the user, such as ghosting and seams. In this work we introduce a new, fully automated calibration algorithm that is tailored to reduce these artifacts, based on consumer-grade hardware. We achieve this goal by repurposing a structured-light scanning setup. A structured-light scanner can generate 3D geometry based on a known intrinsic and extrinsic calibration of its components (projector and RGB camera). We revert this process by providing the resulting 3D model to determine the intrinsic and extrinsic parameters of our setup (including those of a variety of tracking systems). Our system matches features and solves for all parameters in a single pass while respecting the lower quality of our sensory input.

We present a novel approach to mesh deformation that enables simple context sensitive manipulation of 3D geometry. The method is based on locally anisotropic transformations and is extended to global control directions. This allows intuitive directional modeling within an easy to implement framework. The proposed method complements current sculpting paradigms by providing further possibilities for intuitive surface-based editing without the need for additional host geometries. We show the anisotropic deformation to be seamlessly transferable to free boundary parameterization methods, which allows us to solve the hard problem of flattening compression garments in the domain of apparel design.

Projection-based mixed reality is an effective tool to create immersive visualizations on real-world objects. Its wide range of applications includes art installations, education, stage shows, and advertising. In this work, we enhance a multi-projector system for dynamic projection mapping by handling various physical stray-light effects: interreflection, projector black-level, and environmental light in real time for dynamic scenes. We show how all these effects can be efficiently simulated and accounted for at runtime, resulting in significantly improved projection mapping results. By adding a global optimization step, we can further increase the dynamic range of the projection.

Recent publications and art performances demonstrate amazing results using projection mapping. To our knowledge, there exists no multi-projection system that can project onto non-rigid target geometries. This constrains the applicability and quality for live performances with multiple spectators. Given the cost and complexity of current systems, we present a low-cost easy-to-use markerless non-rigid face multi-projection system. It is based on a non-rigid, dense face tracker and a real-time multi-projection solver adapted to imprecise tracking, geometry and calibration. Using this novel system we produce compelling results with only consumer-grade hardware.

Using projection mapping enables us to bring virtual worlds into shared physical spaces. In this paper, we present a novel, adaptable and real-time projection mapping system, which supports multiple projectors and high quality rendering of dynamic content on surfaces of complex geometrical shape. Our system allows for smooth blending across multiple projectors using a new optimization framework that simulates the diffuse direct light transport of the physical world to continuously adapt the color output of each projector pixel. We present a real-time solution to this optimization problem using off-the-shelf graphics hardware, depth cameras and projectors. Our approach enables us to move projectors, depth camera or objects while maintaining the correct illumination, in realtime, without the need for markers on the object. It also allows for projectors to be removed or dynamically added, and provides compelling results with only commodity hardware.

The high peak-to-average power ratio (PAR) of the transmit signal is one serious issue, which occurs in orthogonal frequency-division multiplexing (OFDM). Hence, the application of a PAR reduction algorithm, which controls the peak-power of the transmit signal, is indispensable. In this paper, we consider selected mapping (SLM), a very popular technique for PAR reduction and its recently proposed extension successive SLM. One drawback of (successive) SLM is that the transmission of side information is necessary, which is extraordinarily prone to transmission errors. In this paper, the explicit transmission of this side information is considered. In order to reduce the increase in bit error rates, due to an erroneous detection of the side information, its estimation at the receiver and its mapping to signals embedded into the OFDM frame is optimized. In this case the application of successive SLM is very advantageous compared to the original approach of SLM as the detection error rate can be reduced significantly. Moreover, with successive SLM almost no differences between explicit transmission and perfect knowledge of the side information in terms of bit error rates occur.

A successive scheme for PAR reduction in (MIMO/ SISO) OFDM is presented, where K (parallel/consecutive) OFDM frames are treated jointly. Employing Reed-Solomon codes further candidate OFDM frames are generated and assessed successively; the currently best K are selected for possible transmission. The procedure stops if (i) all K best frames stay below a given tolerable PAR limit, or (ii) the maximally allowed number of candidates is exhausted. Thereby complexity compared to other PAR reduction schemes can be reduced significantly. Analytical derivations show that for PAR limits in the region of the "critical PAR" value xicrit = log(D), with D being the number of carriers, the average number candidates is close to Euler's number e = 2.71828..., which is particularly low.

Selected mapping (SLM) is a popular scheme for peak power reduction in orthogonal frequency-division multiplexing (OFDM) systems. In this letter, the performance of various versions of SLM, among them ordinary and directed SLM, in single- and multi-antenna point-to-point OFDM systems is assessed. Analytic expressions for the distribution of the PAR are derived. Numerical results cover that significant gains over conventional SLM can be achieved by directed SLM.

New schemes for peak-to-average power ratio reduction in orthogonal frequency-division multiplexing (OFDM) systems are proposed. Reed-Solomon (RS) and simplex codes are employed to create a number of candidates, from which the best are selected. Thereby, in contrast to existing approaches, the codes are arranged over a number of OFDM frames rather than over the carriers, hence a combination of the principles of multiple signal representation with selection (as done in selected mapping) and the use of channel coding is present. In particular, in multiple-antenna transmission, the proposed schemes do not cause any additional delay, but due to the utilization of the dimension space, additional gains can be achieved. Moreover, the schemes are very flexible; due to the selection step, any criterion of optimality can be taken into account. Besides multiple-antenna transmission, packet transmission is briefly considered, which, moreover, covers the appealing similarities with incremental redundancy check schemes in automatic repeat request (ARQ) applications and with decoding of codes transmitted over the erasure channel. The performance of the schemes is (using some approximations) derived analytically and is covered by numerical results that are in very good agreement with the theory. Significant gains can be achieved with these very flexible and versatile methods.

A new scheme for peak-to-average power ratio reduction in OFDM systems is proposed which combines the principles of multiple signal representation with selection (as done in selected mapping) and the use of channel coding. Thereby, in contrast to existing approaches, the code is arranged over a number of OFDM frames rather than over the carriers. Given the initial OFDM frames all linear combinations thereof are generated; from that the best are selected. The corresponding generator matrix is identical to that of the Simplex code. Specifically, we consider multi-antenna transmission, where the proposed scheme does not cause any additional delay, but utilize the dimension space adequately. The scheme is very flexible; due to the selection step any criterion of optimality can be taken into account. Performance is derived analytically and is covered by numerical results which are in very good agreement with theory.

In this paper variants of selected mapping are investigated for different MIMO OFDM scenarios (point-to- point, multiple-access, and broadcast channel). Particular focus is on the broadcast scenario, where transmitter side precoding is mandatory which usually increases peak-to-average power ratio (PAR). The combination of (non-linear) precoding with a selected mapping technique leads to a very high computational complexity because it operates on all carriers. This paper introduces a new PAR reducing method which affects only a subset of carriers and therefore saves complexity. Because PAR reduction is achieved by optimizing the sorting in the precoding scheme, this technique is called selected sorting.