Fast Preview Research Articles

Automatic embroidery texture synthesis for garment design and online display

We introduce an automatic texture synthesis-based framework to convert an arbitrary input image into embroidery style art for garment design and online display. Given an input image and some reference textures, we first extract key embroidery regions from the input image using image segmentation. Each segmented region is single-colored and labeled with a stitch style automatically. We then fill these regions with embroidery reference textures via a stitch-style-based texture synthesis method. For each region, our approach maintains color similarity before and after synthesis, along with stitch style consistency. Compared to existing approaches, our method is able to generate digital embroidery patterns with faithful details automatically. Moreover, it can accept diverse input images effectively, enabling a fast preview of the embroidery patterns synthesized on digital garments interactively, and therefore accelerating the workflow from design to production. We validate our method through extensive experimentation and comparison.

A CNN‐based Flow Correction Method for Fast Preview

AbstractEulerian‐based smoke simulations are sensitive to the initial parameters and grid resolutions. Due to the numerical dissipation on different levels of the grid and the nonlinearity of the governing equations, the differences in simulation resolutions will result in different results. This makes it challenging for artists to preview the animation results based on low‐resolution simulations. In this paper, we propose a learning‐based flow correction method for fast previewing based on low‐resolution smoke simulations. The main components of our approach lie in a deep convolutional neural network, a grid‐layer feature vector and a special loss function. We provide a novel matching model to represent the relationship between low‐resolution and high‐resolution smoke simulations and correct the overall shape of a low‐resolution simulation to closely follow the shape of a high‐resolution down‐sampled version. We introduce the grid‐layer concept to effectively represent the 3D fluid shape, which can also reduce the input and output dimensions. We design a special loss function for the fluid divergence‐free constraint in the neural network training process. We have demonstrated the efficacy and the generality of our approach by simulating a diversity of animations deviating from the original training set. In addition, we have integrated our approach into an existing fluid simulation framework to showcase its wide applications.

Additional lossless compression of JPEG images based on BPG

The task of additional lossless compression of JPEG images is considered. We propose to decode JPEG image and recompress it using lossy BPG (Better Portable Graphics) codec based on a subset of the HEVC open video compression standard. Then the decompressed and smoothed BPG image is used for calculation and quantization of DCT coefficients in 8x8 image blocks using quantization tables of the source JPEG image. A difference between obtained quantized DCT coefficients and quantized DCT coefficients of the source JPEG image (prediction error) is calculated. The difference is lossless compressed by a proposed context modeling and arithmetical coding. In this way the source JPEG image is replaced by two files: compressed BPG image and the compressed difference which needed for lossless restoration of the source JPEG image. It is shown that the proposed approach provides compression ratios comparable with state of the art PAQ8, WinZip and STUFFIT file archivers. At the same time BPG images may be used for fast preview of compressed JPEG images.

Interactive Two-Way Shape Design of Elastic Bodies

We present a novel system for interactive elastic shape design in both forward and inverse fashions. Using this system, the user can choose to edit the rest shape or the quasistatic shape of an elastic solid, and obtain the other shape that matches under the quasistatic equilibrium condition at the same time. The development of this system is based on the discovery that inverse quasistatic simulation can be immediately solved by Newton's method with a direct solver. To implement our simulator, we propose a Jacobian matrix evaluation scheme for the inverse elastic problem and we present step length and matrix evaluation techniques that improve the simulation performance. While our simulator is efficient, it is still not fast enough for the system to generate the result in real time. Our solution is a shape initialization method using the recent projective dynamics technique. Shape initialization not only works as a fast preview function during the user editing process, but also speeds up the convergence of quasistatic or inverse quasistatic simulation afterwards. The use of a heterogeneous algorithm structure allows the system to further reduce its preview cost, by utilizing the power of both the CPU and the GPU. Our experiment demonstrates that the whole system is fast, robust, and convenient for the designer to use in both forward and inverse elastic shape design. It can handle a variety of nonlinear elastic material models, and its runtime performance has space for more improvement.

Stress-aware large-scale mesh editing using a domain-decomposed multigrid solver

In this paper, we develop a domain-decomposed subspace and multigrid solver to analyze the stress distribution for large-scale finite element meshes with millions of degrees of freedom. Through the domain decomposition technique, the shape editing directly updates the data structure of local finite element matrices. Doing so avoids the expensive factorization step in a direct solver and provides users with a progressive feedback of the stress distribution corresponding to the mesh operations: a fast preview is achieved through the subspace solver, and the multigrid solver refines the preview result if the user needs to examine the stress distribution carefully at certain design stages. Our system constructs the subspace for stress analysis using reduced constrained modes and builds a three-level multigrid solver through the algebraic multigrid method. We remove mid-edge nodes and lump unknowns with the Schur complement method. The updating and solving of the large global stiffness matrix are implemented in parallel after the domain decomposition. Experimental results show that our solver outperforms the parallel Intel MKL solver. Speedups of ▪ can be achieved for large-scale meshes with reasonable pre-computation costs when setting the stopping criterion of the multigrid solver to be 1e−3 relative error.

Low-Complexity Enhancement Layer Compression for Scalable Lossless Video Coding Based on HEVC

Lossless compression is desired, especially for professional applications like medical imaging. However, scalability may be necessary to transmit a fast preview of pictures when the channel capacity is limited. Furthermore, there may be the need for random access to single frames of a losslessly reconstructed video. We present and evaluate a lossy-to-lossless scalable video coding system in which the scalability is achieved by using a lossy base layer (BL) in conjunction with lossless compression of the reconstruction error in the enhancement layer (EL). High Efficiency Video Coding (HEVC) is employed for encoding the BL. For compression of the EL, we propose a low-complexity scheme called sample-based weighted prediction for EL coding (SELC). Furthermore, EL compression using JPEG-LS and the scalable extension of HEVC (SHVC) are evaluated. The performance of scalable coding using each of these three methods is compared with lossless single-layer (SL) coding using the intra-main RExt configuration. Experimental results show that the scalable coding with SELC achieves average bitrate savings of 7.3% compared with the lossless SL coding, while average bitrate reductions of only 6.3% and 3.9% are obtained using JPEG-LS and SHVC, respectively. Concerning runtime, the additional encoder runtimes of SELC and JPEG-LS compared with the BL coding are negligible. In contrast to that, the runtime of the SHVC EL encoder is much higher and similar to the runtime of the BL encoder.

Interactive Generation of Realistic Facial Wrinkles from Sketchy Drawings

AbstractSynthesizing facial wrinkles has been tackled either by a long process of manual sculpting on 3D models, or using automatic methods that do not allow for user interaction or artistic expression. In this paper, we propose a method that accepts interactive sketchy drawings depicting wrinkle patterns, and synthesizes realistic looking wrinkles on faces. The method inherits the simplicity of sketching, making it possible for artists as well as novice users to generate realistic facial detail very efficiently, allowing fast preview for physical makeup, or aging simulations for fun and professional applications. All strokes are used to infer the wrinkles, retaining the expressiveness of the sketches and realism of the final result at the same time. This is achieved by designing novel multi‐scale statistics tailored to the wrinkle geometry and coupled to the sketch interpretation method. The statistics capture the cross‐sectional profiles of wrinkles at different scales and parts of a face. The strokes are augmented with the statistics extracted from given example face models, and applied to an input face model interactively. The interface gives the user control over the shapes and scales of wrinkles via sketching while adding extra details required for realism automatically.

Incremental BVH construction for ray tracing

We propose a new method for incremental construction of Bounding Volume Hierarchies (BVHs). Despite the wide belief that the incremental construction of BVH is inefficient we show that our method incrementally constructs a BVH with quality comparable to the best SAH builders. We illustrate the versatility of the proposed method using a flexible parallelization scheme that opens new possibilities for combining different BVH construction heuristics. We demonstrate the usage of the method in a proof-of-concept application for real-time preview of data streamed over the network. We believe that our method will renew the interest in incremental BVH construction and it will find its applications in ray tracing based remote visualizations and fast previews or in interactive scene editing applications handling very large data sets.

Fast reconstruction of off-axis digital holograms based on digital spatial multiplexing.

A method for fast reconstruction of off-axis digital holograms based on digital multiplexing algorithm is proposed. Instead of the existed angular multiplexing (AM), the new method utilizes a spatial multiplexing (SM) algorithm, in which four off-axis holograms recorded in sequence are synthesized into one SM function through multiplying each hologram with a tilted plane wave and then adding them up. In comparison with the conventional methods, the SM algorithm simplifies two-dimensional (2-D) Fourier transforms (FTs) of four N*N arrays into a 1.25-D FTs of one N*N arrays. Experimental results demonstrate that, using the SM algorithm, the computational efficiency can be improved and the reconstructed wavefronts keep the same quality as those retrieved based on the existed AM method. This algorithm may be useful in design of a fast preview system of dynamic wavefront imaging in digital holography.

GPU-based iterative transmission reconstruction in 3D ultrasound computer tomography

As today’s standard screening methods frequently fail to detect breast cancer before metastases have developed, early diagnosis is still a major challenge. With the promise of high-quality volume images, three-dimensional ultrasound computer tomography is likely to improve this situation, but has high computational needs. In this work, we investigate the acceleration of the ray-based transmission reconstruction by a GPU-based implementation of the iterative numerical optimization algorithm TVAL3. We identified the regular and transposed sparse-matrix–vector multiply as the performance limiting operations. For accelerated reconstruction we propose two different concepts and devise a hybrid scheme as optimal configuration. In addition we investigate multi-GPU scalability and derive the optimal number of devices for our two primary use-cases: a fast preview mode and a high-resolution mode. In order to achieve a fair estimation of the speedup, we compare our implementation to an optimized CPU version of the algorithm. Using our accelerated implementation we reconstructed a preview 3D volume with 24,576 unknowns, a voxel size of (8 mm)3 and approximately 200,000 equations in 0.5 s. A high-resolution volume with 1,572,864 unknowns, a voxel size of (2mm)3 and approximately 1.6 million equations was reconstructed in 23 s. This constitutes an acceleration of over one order of magnitude in comparison to the optimized CPU version.

On the use of hierarchical prediction structures for efficient summary generation of H.264/AVC bitstreams

Video summarization refers to an important set of abstraction techniques aimed to provide a compact representation of the video essential to effectively browse and retrieve video content from multimedia repositories. Most of these video summarization techniques, such as image storyboards, video skims and fast previews, are based on selecting some frames or segments. H.264/AVC has become a widely accepted coding standard and is expected that many of the content will be available in this format soon. This paper proposes a generic model of video summarization especially suitable for generating summaries of H.264/AVC bitstreams in a highly efficient manner, using the concept of temporal scalability via hierarchical prediction structures. Along with the model, specific examples of summarization techniques are given to prove the utility of the model.

Tensor Clustering for Rendering Many‐Light Animations

AbstractRendering animations of scenes with deformable objects, camera motion, and complex illumination, including indirect lighting and arbitrary shading, is a long‐standing challenge. Prior work has shown that complex lighting can be accurately approximated by a large collection of point lights. In this formulation, rendering of animation sequences becomes the problem of efficiently shading many surface samples from many lights across several frames. This paper presents a tensor formulation of the animated many‐light problem, where each element of the tensor expresses the contribution of one light to one pixel in one frame. We sparsely sample rows and columns of the tensor, and introduce a clustering algorithm to select a small number of representative lights to efficiently approximate the animation. Our algorithm achieves efficiency by reusing representatives across frames, while minimizing temporal flicker. We demonstrate our algorithm in a variety of scenes that include deformable objects, complex illumination and arbitrary shading and show that a surprisingly small number of representative lights is sufficient for high quality rendering. We believe out algorithm will find practical use in applications that require fast previews of complex animation.

A JAVA-based DICOM server with integration of clinical findings and DICOM-conform data encryption

The transfer of large amounts of medical data within heterogeneous hard and software infrastructures and the exploitation of distributed resources require a fast, secure, and platform-independent data exchange. To avoid costly vendor-specific solutions, a DICOM server was implemented in JAVA. Data access was enabled via internet browser technology. Relevant patient and image acquisition information was extracted from the DICOM images and stored into a relational database. Patient information such as radiological findings were transferred from the Radiological Information System into the database. Image data were accessed either by a fast preview tool or using a JAVA-based DICOM viewer. Since data security mechanisms are not yet part of the DICOM standard, a DICOM-conform encryption of sensitive patient data was implemented. The method allowed a dynamic selection of the data to be encrypted. Integrating this module into the image server enabled the fast and secure transfer of image data across insecure networks as well as long-term storage on CD-Recordables.