Abstract In recent years, it becomes possible to extract hair information for hair reconstruction from multiple cameras or monocular camera. Using a single image as the input avoids the high cost setups and complex calibration compared to multiviewed reconstruction. Taking advantage of an extendible hairstyle database, this paper introduced Struct2Hair, a novel single‐viewed hair modelling approach by extracting hair shape descriptor (HSD). The HSD is defined as the fundamental structure‐aware feature, which is a combination of critical shapes in a hairstyle. A complete dataset of critical hair shapes is constructed from a known database of three‐dimensional (3D) hair models. We first analyze the input two‐dimensional (2D) image to extract the orientation information and 2D hair sketch automatically. The extracted information is then used to retrieve the corresponding critical shapes with optimization to build the robust HSD. Finally, the HSD constructs a weighted 3D hair orientation field to guide full‐head hair model generation. Our method can preserve local geometric features of hair and retain the whole shape of the hairstyle globally owing to the HSD, which will benefit further hair editing and stylization.

Abstract Destruction in video games traditionally use pre-fracturing techniques to efficiently swap out game objects at run-time, which requires artists to create multiple models in various states of destruction. Real-time methods require less design time and can produce more realistic results but often come at a cost of performance. If real-time methods can perform at similar levels as tradition pre-fracturing means, this could increase the current standards of realistic destruction in video games. This paper explores and implements real-time fracturing techniques, comparing these to traditional pre-fracturing methods in terms of visual realism and performance. The results of the implementation were then distributed in an online questionnaire, to view how participants perceived the differences of both techniques and whether the visual or performance aspects affected their preferences of one method over the other.

To better capture the shapes as well as the rich dynamics of hair, image based modelling techniques have been developed for reconstructing their 3D geometry and important visual features. Most hair images contain inevitable noises which impair reconstructed hair models. Therefore we propose to pre-process hair images and provide an orientation map of hair strands to enhance the follow-on modelling. To demonstrate the usage of pre-processing techniques, we apply our pre-processing results for bas-relief stylisation and modelling of hair from image inputs. We compare different techniques to estimate hair orientations, adopting four types of filter mechanisms. Our analysis of their performance sheds insight on designing a suitable pre-processing technique for hair reconstruction from images. Several examples of bas-relief creation validate the effectiveness of the proposed approach.

A generalized version of orthogonal frequency division multiplexing interleave division multiple access (OFDM-IDMA) referred to as grouped OFDM-IDMA (G-OFDM-IDMA) is introduced in this paper. By dividing users into groups and transmitting each group's data only on some (as opposed to all) subcarriers, G-OFDM-IDMA can have much lower decoding complexity compared with conventional OFDM-IDMA while preserving the bit error probability (BEP) performance and the bandwidth efficiency. The user grouping problem is formulated into an integer linear programming problem whose suboptimal solution is proposed and compared with the lower bound. The optimization complexity issue is also addressed. Simulations are carried out to test the performance of G-OFDM-IDMA under various system configurations. It is observed that up to 80% complexity could be saved when the conventional OFDM-IDMA is substituted by G-OFDM-IDMA configured according to the suboptimal grouping solution.

The battery nonlinearity has never been considered for energy analysis in relay networks. In this letter, we adopt the realistic nonlinear battery model, apply the battery energy consumption results in to general relay networks, investigate the optimum and suboptimum energy allocation solutions for relaying transmission, and establish the relay selection criterion from the battery energy efficiency perspective. Our analyses and comparisons show that relaying does not always increase the system energy efficiency. We further establish closed-form conditions that can be easily checked to determine whether the relay transmission is preferable to the direct transmission. Numerical examples are also presented to verify these results.

In a case study of the waveform design for target estimation in MIMO sensing, [9] developed the optimum waveform design in the presence of colored noise, as well as the joint robust transmitter and receiver designs. Three criteria, namely mutual information (MI), minimum mean square error (MMSE), and normalized MSE (NMSE), are considered. The relationship between the essential measure MI in communications and the commonly adopted MSE indicators for sensing has created a vision of communications-inspired sensing. In this paper, we will further investigate this relationship by analyzing the sensitivity of the optimum design to the overestimation error. For each of the three criteria, we derive the explicit formula for the error mode strength threshold, above which the error mode would consume nonzero transmit power and the original waveform design will be inevitably altered. We also develop a normalized NMSE indicator to measure the estimation performance variation induced by the error mode. Both analytical and numerical results confirm that the optimum waveform designs based on the three criteria do not show significant performance deterioration. While the NMSE-based optimum solution is always more sensitive to the overestimation error than the MI-based one, there is no universal relationship between these two criteria and MMSE.

Rapid and accurate timing synchronization is the first and foremost task in ultra-wideband (UWB) systems. The timing with dirty templates (TDT) algorithm introduced in [10] is a promising method with low complexity and relaxed operation conditions in the presence of unknown time hopping and multipath channel. Its optimality, however, remains unexplored. In this paper, we develop the maximum-likelihood (ML) timing algorithm and obtain its optimum training sequence. We show that the optimum training sequence of the ML timing estimator coincides with that of the TDT algorithm. In addition, we prove that, using this training sequence, the ML algorithm can be simplified, and that the simplified ML (SML) is equivalent to TDT.

In the distributed space time block coded (DSTBC) orthogonal frequency division multiplexing (OFDM) system (DSTBC-OFDM), since the transmit antennas belong to different nodes that are distributed, there may exist multiple carrier frequency offsets (CFOs) to the transmitters at the receiver. Several kinds of equalization techniques, which intend to mitigate the intercarrier interference (ICI) when detecting symbols, are compared in terms of the BER performance. And an equalization method based on iterative ICI cancellation is proposed. Simulation results show that when the difference of normalized CFOs (with respect to the subcarrier spacing) between distributed transmitters is not more than 0.2, the proposed iterative ICI cancellation method could combat ICI effectively at very low computational cost. However, in case of large difference of normalized CFOs, i.e., 0.4, the frequency offsets could cancel the space diversity gain of distributed STBC totally even when ideal ICI cancellation is assumed, and the performance is close to that of OFDM system using single transmit antenna without space time block coding

In this paper, the performance of distributed space-time block coded (DSTBC) orthogonal frequency-division multiplexing (OFDM) system (DSTBC-OFDM) with the presence of carrier frequency offsets is investigated. Since the transmit antennas belong to different nodes that are distributed, there may exist multiple carrier frequency offsets to the transmitters at the receiver of DSTBC-OFDM system. The system model of DSTBC-OFDM with multiple carrier frequency offsets is given. Then we propose a frequency-domain detector to cancel the inter-symbol interference and the inter-carrier interference when detecting the symbols. The proposed detector has a reasonable performance and a moderate computational complexity. Simulation results show that the detector works very well when the carrier frequency difference between the distributed transmitters is small