Search Results

Now showing 1 - 10 of 37
  • Item
    Example-based Interpolation and Synthesis of Bidirectional Texture Functions
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Ruiters, Roland; Schwartz, Christopher; Klein, Reinhard; I. Navazo, P. Poulin
    Bidirectional Texture Functions (BTF) have proven to be a well-suited representation for the reproduction of measured real-world surface appearance and provide a high degree of realism. We present an approach for designing novel materials by interpolating between several measured BTFs. For this purpose, we transfer concepts from existing texture interpolation methods to the much more complex case of material interpolation. We employ a separation of the BTF into a heightmap and a parallax compensated BTF to cope with problems induced by parallax, masking and shadowing within the material. By working only on the factorized representation of the parallax compensated BTF and the heightmap, it is possible to efficiently perform the material interpolation. By this novel method to mix existing BTFs, we are able to design plausible and realistic intermediate materials for a large range of different opaque material classes. Furthermore, it allows for the synthesis of tileable and seamless BTFs and finally even the generation of gradually changing materials following user specified material distribution maps.
  • Item
    Perceptually Motivated Real-Time Compression of Motion Data Enhanced by Incremental Encoding and Parameter Tuning
    (The Eurographics Association, 2013) Firouzmanesh, Amirhossein; Cheng, Irene; Basu, Anup; M.- A. Otaduy and O. Sorkine
    We address the problem of efficient real-time motion data compression considering human perception. Using incremental encoding plus a database of motion primitives for each key point, our method achieves a higher or competitive compression rate with less online overhead. Trade-off between visual quality and bandwidth usage can be tuned by varying a single threshold value. A user study was performed to measure the sensitivity of human subjects to reconstruction errors in key rotation angles. Based on these evaluations we are able to perform lossy compression on the motion data without noticeable degradation in rendered qualities. While achieving real-time performance, our technique outperforms other methods in our experiments by achieving a compression ratio exceeding 50 : 1 on regular sequences.
  • Item
    Using Webcams for Product Presentations in HTML5
    (The Eurographics Association, 2013) Borg, Mathias; Kraus, Martin; Miguel Chover and A. Augusto de Sousa
    The Media Capture and Streams API ("getUserMedia API") enables plug-in free webcam support in HTML5. This opens new ways of interacting with visualisations using open web standards. In this work, two techniques are proposed that employ the user's webcam for interactive product presentations on websites. The first technique tracks the user's face and uses its position to create the impression of a user-controlled rotation of a product by displaying a sequence of product images for different view points. The second technique uses photographs of a product with reflections of coloured patterns to render the user's webcam stream as a reflection in the product presentation. Thus, users in front of a webcam are able to see their virtual reflection in a picture of a real product in real time. Our implementation of two prototypes shows that it is technically possible to implement these features with HTML5 and JavaScript only.
  • Item
    A Sensor Based Approach to Outdoor Illumination Estimation for Augmented Reality Applications on Mobile Devices
    (The Eurographics Association, 2013) Barreira, João; Magalhães, Luís; Bessa, Maximino; Miguel Chover and A. Augusto de Sousa
    Realistic Augmented Reality applications require integrating virtual objects in the real world in a seamless visual way. The main problem to obtain a perfect visual augmentation is rendering the virtual objects with consistent illumination. In this paper, we present a novel approach to estimate outdoor illumination for Augmented Reality applications on mobile devices based on information acquired from sensors. We use an ambient light sensor to automatically detect in real-time the scene illuminance, which is used to simulate the actual lighting conditions. As outdoor illumination is mostly dependent on the weather, we derived the sky/sun illumination parameters from the light sensor data based on the IESNA sky model. The sunlight direction is estimated based on information from the GPS, date and time of the day. The result is a practical solution for outdoor illumination estimation handling light changes under natural conditions and applying them to the rendering of virtual objects in the real scene.
  • Item
    Latency Considerations of Depth-first GPU Ray Tracing
    (The Eurographics Association, 2014) Guthe, Michael; Eric Galin and Michael Wand
    Despite the potential divergence of depth-first ray tracing [AL09], it is nevertheless the most efficient approach on massively parallel graphics processors. Due to the use of specialized caching strategies that were originally developed for texture access, it has been shown to be compute rather than bandwidth limited. Especially with recents developments however, not only the raw bandwidth, but also the latency for both memory access and read after write register dependencies can become a limiting factor. In this paper we will analyze the memory and instruction dependency latencies of depth first ray tracing. We will show that ray tracing is in fact latency limited on current GPUs and propose three simple strategies to better hide the latencies. This way, we come significantly closer to the maximum performance of the GPU.
  • Item
    Automatic Convergence Adjustment for Stereoscopy using Eye Tracking
    (The Eurographics Association, 2013) Fisker, Martin; Gram, Kristoffer; Thomsen, Kasper Kronborg; Vasilarou, Dimitra; Kraus, Martin; Miguel Chover and A. Augusto de Sousa
    When using stereoscopic displays, decoupling between convergence and accommodation can cause eyestrain. This paper proposes an adjustment method to automatically fit convergence at user fixation depth to accommodation by using eye tracking. Two different adjustment methods are proposed: one binocular, adjusting the images for both eyes, and one monocular, which adjusts only the image for the non-dominant eye. Preliminary results suggest better user comfort and a preference for binocular adjustment in high adjustment scenarios, while the adjustment is less noticeable with the monocular system.
  • Item
    Stylized and Performative Gaze for Character Animation
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Pejsa, Tomislav; Mutlu, Bilge; Gleicher, Michael; I. Navazo, P. Poulin
    Existing models of gaze motion for character animation simulate human movements, incorporating anatomical, neurophysiological, and functional constraints. While these models enable the synthesis of humanlike gaze motion, they only do so in characters that conform to human anatomical proportions, causing undesirable artifacts such as cross-eyedness in characters with non-human or exaggerated human geometry. In this paper, we extend a state-of-the- art parametric model of human gaze motion with control parameters for specifying character geometry, gaze dynamics, and performative characteristics in order to create an enhanced model that supports gaze motion in characters with a wide range of geometric properties that is free of these artifacts. The model also affords ''staging effects'' by offering softer functional constraints and more control over the appearance of the character's gaze movements. An evaluation study showed that the model, compared with the state-of-the-art model, creates gaze motion with fewer artifacts in characters with non-human or exaggerated human geometry while retaining their naturalness and communicative accuracy.
  • Item
    A Novel Projection Technique with Detail Capture and Shape Correction for Smoke Simulation
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Wu, Xiaoyue; Yang, Xubo; Yang, Yang; I. Navazo, P. Poulin
    Smoke simulation on a large grid is quite time consuming and most of the computation time is spent on the projection step.We present a novel projection method which produces quite similar visual results as those produced with the traditional projection method, but uses much less computation time. Our method includes two steps: detail-capture and shape-correction. The first step preserves most of the smoke details using an efficient DST (Discrete Sine Transformation) Poisson Solver with auxiliary boundary sweeping. The second step maintains the overall flow shape by solving a correcting Poisson equation on a coarse grid. Our algorithm is very fast and quite easy to implement. Experiments show that our projection is approximately 10-30 times faster than the traditional projection with PCG(Preconditioned Conjugate Gradient), while convincingly preserving both the flow details and the overall shape of the smoke.
  • Item
    Volume Ray Casting quality estimation in terms of Peak Signal-to-Noise Ratio
    (The Eurographics Association, 2013) Gavrilov, Nikolay; Turlapov, V.; Miguel Chover and A. Augusto de Sousa
    In spite of a large number of techniques aimed for improvement of Direct Volume Rendering (DVR) quality and performance proposed in the literature, there is a lack of approaches for numerical quality estimation of the images obtained by visualization of medical and scientific volumetric datasets. In this paper we propose a method to estimate sampling artefacts. Using the proposed estimation method we compare different RC algorithms to expose optimal ones in quality-performance criteria.
  • Item
    Skeleton-based Joints Position Detection
    (The Eurographics Association, 2014) Madaras, Martin; Piovarci, Michal; Kovacovský, Tomás; Mathias Paulin and Carsten Dachsbacher
    We present a system for detection of joint positions in scans of articulated models. Our method is based purely on skeletons extracted from scanned point clouds of input models. First, skeletons are extracted from scans and then an estimation of possible matches between skeletons is performed. The matches are evaluated and sorted out. The whole matching process is fully automatic, but some user-driven suggestions can be included. Finally, we pick the best matching of skeletons and create a union-skeleton containing all the nodes from all the skeletons. We find nodes in the union-skeleton with rotation changes higher than the predefined threshold. We take these nodes as joints and visualize them in original scans.