PG: Pacific Graphics Short Papers

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Browsing PG: Pacific Graphics Short Papers by Subject "and texture"

Now showing 1 - 7 of 7
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    Adaptive Measurement of Anisotropic Material Appearance
    (The Eurographics Association, 2017) Vávra, Radomir; Filip, Jiri; Jernej Barbic and Wen-Chieh Lin and Olga Sorkine-Hornung
    We present a practical adaptive method for acquisition of the anisotropic BRDF. It is based on a sparse adaptive measurement of the complete four-dimensional BRDF space by means of one-dimensional slices which form a sparse four-dimensional structure in the BRDF space and which can be measured by continuous movements of a light source and a sensor. Such a sampling approach is advantageous especially for gonioreflectometer-based measurement devices where the mechanical travel of a light source and a sensor creates a significant time constraint. In order to evaluate our method, we perform adaptive measurements of three materials and we simulate adaptive measurements of ten others. We achieve a four-times lower reconstruction error in comparison with the regular non-adaptive BRDF measurements given the same count of measured samples. Our method is almost twice better than a previous adaptive method, and it requires from two- to five-times less samples to achieve the same results as alternative approaches.
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    Automatic Aesthetics-based Lighting Design with Global Illumination
    (The Eurographics Association, 2014) Léon, Vincent; Gruson, Adrien; Cozot, Rémi; Bouatouch, Kadi; John Keyser and Young J. Kim and Peter Wonka
    In computer graphics, lighting plays an important role in the appearance of a scene. A change in the configuration of light sources can lead to different aesthetics in the final rendered image. Lighting design becomes increasingly complex when using sophisticated global illumination techniques. In this paper, we present a new approach to automatically design the lighting configuration according to the aesthetic goal specified by the user as a set of target parameters. Target parameters are used to set up an objective function which is minimized using an optimization method. The results show that our method can be used to automatically design a lighting configuration that will give to the final image a classic photographic look.
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    Fast Random Sampling of Triangular Meshes
    (The Eurographics Association, 2013) Sik, Martin; Krivanek, Jaroslav; Bruno Levy and Xin Tong and KangKang Yin
    We present a simple and fast algorithm for generating randomly distributed points on a triangle mesh with probability density specified by a two-dimensional texture. Efficiency is achieved by resampling the density texture on an adaptively subdivided version of the input mesh. This allows us to generate the samples up to 40 x faster than the rejection sampling algorithm, the fastest existing alternative. We demonstrate the algorithm in two applications: fast placement of hair roots on a surface and sampling of illumination from a complex luminaire. Part of our mesh sampling procedure is a new general acceleration technique for drawing samples from a 1D discrete probability distribution whose utility extends beyond the mesh sampling problem.
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    Local Detail Enhancement for Volume Rendering under Global Illumination
    (The Eurographics Association, 2016) Zheng, Jinta; Zhang, Tianjin; Qin, Jing; Eitan Grinspun and Bernd Bickel and Yoshinori Dobashi
    We present a novel method for realistic perception enhanced volume rendering. Compared with traditional lighting systems, that either tend to eliminate important local shapes and details in volume data or cannot offer interactive global illumination, our method can enhance the edges and curvatures within a volume under global illumination through a user-friendly interface. We first propose an interactive volumetric lighting model to both simulate scattering and enhance the local detail information. In this model, users only need to determine a key light source. Next, we propose a new cue to intensify the shape perception by enhancing the local edges and details. The cue can be pre-computed and thus we can still keep the rendering process running real-time. Experiments on a variety of volume data demonstrate that the proposed method can generate more details, and hence more realistic rendering results.
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    Modified Filtered Importance Sampling for Virtual Spherical Gaussian Lights
    (The Eurographics Association, 2016) Tokuyoshi, Yusuke; Eitan Grinspun and Bernd Bickel and Yoshinori Dobashi
    This paper proposes a modification of the filtered importance sampling (FIS) method, and improves the quality of virtual spherical Gaussian light (VSGL) based real-time glossy indirect illumination using this modification. The original FIS method produces large overlaps of and gaps between filtering kernels for high-frequency probability density functions (PDFs). This is because the size of the filtering kernel is determined using the PDF at the sampled center of the kernel. To reduce those overlaps and gaps, this paper determines the kernel size using the integral of the PDF in the filtering kernel. Our key insight is that these integrals are approximately constant, if kernel centers are sampled using stratified sampling. Therefore, an appropriate kernel size can be obtained by solving this integral equation. Using the proposed kernel size for FIS-based VSGL generation, undesirable artifacts are significantly reduced with a negligibly small overhead.
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    Perceptually Optimised Illumination for Seamless Composites
    (The Eurographics Association, 2014) Chalmers, Andrew; Choi, Jong Jin; Rhee, Taehyun; John Keyser and Young J. Kim and Peter Wonka
    Realistic illumination in composition is important for a seamless mixture between the virtual and real world objects in visual effects and mixed reality. The seamlessness is the measure of how perceivably apparent the synthetic object in the final composition is, and how indistinguishable it is from the photographed scene. Given that the ultimate receiver of image information is the human eye, the metric is determined by the Human Visual System (HVS). We conducted a series of psychophysical studies to observe and capture the thresholds of the HVS's ability to perceive illumination inconsistencies between the rendered subject and the photographed scene. Based on our observations, we find perceptually optimised thresholds for reducing resources across resolution and dynamic range of the radiance map (RM) for image based lighting (IBL). We evaluated our thresholds to illuminate virtual objects for seamless composition with photographed scenes.
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    Visibility Filtering for Producing Indirect Illumination
    (The Eurographics Association, 2014) Chen, Yu-Jung; Yen, Chen-Yu; Chen, Yen-Yu; Chen, Wei-Chao; Chien, Shao-Yi; John Keyser and Young J. Kim and Peter Wonka
    Indirect illumination is one of the most visually significant effects for a synthesized image. In order to render such effects at interactive rates, it is important to resolve the visibility between surfaces efficiently. In this work, we propose to approximate visibility by representing the scene through point proxies and hash them into voxels. The indirect illumination is then rendered in two stages. First, we cast sparse shadow rays to march and collect visible voxels for each low-resolution deferred pixel. The list of visible voxels are then processed using the proposed Visibility Filter (VF) to collect voxels missed from the first stage. Afterward, we properly weight the visible voxels as light sources to produce the full resolution image. Our method runs at interactive rates at 1.3 fps to 2.3 fps on GPUs with pleasing visual quality, in particular for glossy reflections.