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Efficient Ray Tracing Through Aspheric Lenses and Imperfect Bokeh Synthesis

COMPUTER GRAPHICS FORUM 2016年第4期35卷 99-105页

作者： Joo, Hyuntae Kwon, Soonhyeon Lee, Sangmin Eisemann, Elmar Lee, Sungkil Sungkyunkwan Univ Seoul South Korea Delft Univ Technol NL-2600 AA Delft Netherlands

We present an efficient ray-tracing technique to render bokeh effects produced by parametric aspheric lenses. Contrary to conventional spherical lenses, aspheric lenses do generally not permit a simple closed-form solution of ray-surface intersections. We propose a numerical root-finding approach, which uses tight proxy surfaces to ensure a good initialization and convergence behavior. Additionally, we simulate mechanical imperfections resulting from the lens fabrication via a texture-based approach. Fractional Fourier transform and spectral dispersion add additional realism to the synthesized bokeh effect. Our approach is well-suited for execution on graphics processing units (GPUs) and we demonstrate complex defocus-blur and lens-flare effects.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash display algorithms

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Thumbnail galleries for procedural models

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COMPUTER GRAPHICS FORUM 2014年第2期33卷 361-370页

作者： Lienhard, S. Specht, M. Neubert, B. Pauly, M. Mueller, P. Esri R&D Ctr Zurich Zurich Switzerland Ecole Polytech Fed Lausanne LGG Lausanne Switzerland

Procedural modeling allows for the generation of innumerable variations of models from a parameterized, conditional or stochastic rule set. Due to the abstractness, complexity and stochastic nature of rule sets, it is often very difficult to have an understanding of the diversity of models that a given rule set defines. We address this problem by presenting a novel system to automatically generate, cluster, rank, and select a series of representative thumbnail images out of a rule set. We introduce a set of view attributes' that can be used to measure the suitability of an image to represent a model, and allow for comparison of different models derived from the same rule set. To find the best thumbnails, we exploit these view attributes on images of models obtained by stochastically sampling the parameter space of the rule set. The resulting thumbnail gallery gives a representative visual impression of the procedural modeling potential of the rule set. Performance is discussed by means of a number of distinct examples and compared to state-of-the-art approaches.

关键词： Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture/Image Generation&mdash display algorithms I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling&mdash Geometric algorithms languages and systems I.5.3 [Pattern Recognition]: Clustering&mdash Similarity measures

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Optimizing stereo-to-multiview conversion for autostereoscopic displays

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COMPUTER GRAPHICS FORUM 2014年第2期33卷 63-72页

作者： Chapiro, Alexandre Heinzle, Simon Aydin, Tunc Ozan Poulakos, Steven Zwicker, Matthias Smolic, Aljosa Gross, Markus Disney Res Zurich Zurich Switzerland Swiss Fed Inst Technol Zurich Switzerland Univ Bern CH-3012 Bern Switzerland

We present a novel stereo-to-multiview video conversion method for glasses-free multiview displays. Different from previous stereo-to-multiview approaches, our mapping algorithm utilizes the limited depth range of autostereoscopic displays optimally and strives to preserve the scene's artistic composition and perceived depth even under strong depth compression. We first present an investigation of how perceived image quality relates to spatial frequency and disparity. The outcome of this study is utilized in a two-step mapping algorithm, where we (i) compress the scene depth using a non-linear global function to the depth range of an autostereoscopic display and (ii) enhance the depth gradients of salient objects to restore the perceived depth and salient scene structure. Finally, an adapted image domain warping algorithm is proposed to generate the multiview output, which enables overall disparity range extension.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics] Picture/Image Generation&mdash display algorithms I.4.8 [Image Processing and Computer Vision] Scene Analysis&mdash Stereo

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Real-time Texture Synthesis and Concurrent Random-access Rendering for Low-cost GPU Chip Design

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COMPUTER GRAPHICS FORUM 2016年第7期35卷 87-95页

作者： Zhang, L. Fenney, S. Escribano, F. Imaginat Technol Ltd Hyderabad Andhra Pradesh India

Numerous algorithms have been researched in the area of texture synthesis. However, it remains difficult to design a low-cost synthesis scheme capable of generating high quality results while simultaneously achieving real-time performance. Additional challenges include making a scheme parallel and being able to partially render/synthesize high-resolution textures. Furthermore, it would be beneficial for a synthesis scheme to be able to incorporate Texture Compression and minimize the bandwidth usage, especially on mobile devices. In this paper, we propose a practical method which has low computational complexity and produces textures with small storage requirements. Through use of an index table, random access of the texture is another essential advantage, with which parallel rendering becomes feasible including generation of mip-map sequences. Integrating the index table with existing compression algorithms, for example ETC or PVRTC, the bandwidth is further reduced and avoids the need for a separate, computationally expensive pass to compress the synthesized output. It should be noted that our texture synthesis achieves real-time performance and low power consumption even on mobile devices, for which texture synthesis has been traditionally considered too expensive.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash display algorithms

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A flexible multi-volume shader framework for arbitrarily intersecting multi-resolution datasets

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IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2007年第6期13卷 1584-1591页

作者： Plate, John Holtkaemper, Thorsten Froehlich, Bernd Bauhaus Univ Weimar Weimar Germany

We present a powerful framework for 3D-texture-based rendering of multiple arbitrarily intersecting volumetric datasets. Each volume is represented by a multi-resolution octree-based structure and we use out-of-core techniques to support extremely large volumes. Users define a set of convex polyhedral volume lenses, which may be associated with one or more volumetric datasets. The volumes or the lenses can be interactively moved around while the region inside each lens is rendered using interactively defined multi-volume shaders. Our rendering pipeline splits each lens into multiple convex regions such that each region is homogenous and contains a fixed number of volumes. Each such region is further split by the brick boundaries of the associated octree representations. The resulting puzzle of lens fragments is sorted in front-to-back or back-to-front order using a combination of a view-dependent octree traversal and a GPU-based depth peeling technique. Our current implementation uses slice-based volume rendering and allows interactive roaming through multiple intersecting multi-gigabyte volumes.

关键词： Lenses Rendering Computer Graphics Pipelines Geometry Spatial Resolution Petroleum Graphics Data Visualization Solids displays display algorithms Multi Volume Visualization Constructive Solid Geometry Shading

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Visualization of Particle-based Data with Transparency and Ambient Occlusion

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COMPUTER GRAPHICS FORUM 2015年第3期34卷 151-160页

作者： Staib, Joachim Grottel, Sebastian Gumhold, Stefan Tech Univ Dresden Chair Comp Graph & Visualizat Dresden Germany

Particle-based simulation techniques, like the discrete element method or molecular dynamics, are widely used in many research fields. In real-time explorative visualization it is common to render the resulting data using opaque spherical glyphs with local lighting only. Due to massive overlaps, however, inner structures of the data are often occluded rendering visual analysis impossible. Furthermore, local lighting is not sufficient as several important features like complex shapes, holes, rifts or filaments cannot be perceived well. To address both problems we present a new technique that jointly supports transparency and ambient occlusion in a consistent illumination model. Our approach is based on the emission-absorption model of volume rendering. We provide analytic solutions to the volume rendering integral for several density distributions within a spherical glyph. Compared to constant transparency our approach preserves the three-dimensional impression of the glyphs much better. We approximate ambient illumination with a fast hierarchical voxel cone-tracing approach, which builds on a new real-time voxelization of the particle data. Our implementation achieves interactive frame rates for millions of static or dynamic particles without any preprocessing. We illustrate the merits of our method on real-world data sets gaining several new insights.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash display algorithms I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism&mdash Color shading shadowing and texture I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism&mdash Raytracing

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Layered Reconstruction for Defocus and Motion Blur

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COMPUTER GRAPHICS FORUM 2014年第4期33卷 81-92页

作者： Munkberg, Jacob Vaidyanathan, Karthik Hasselgren, Jon Clarberg, Petrik Akenine-Moller, Tomas Intel Corp Santa Clara CA 95051 USA Lund Univ S-22100 Lund Sweden

Light field reconstruction algorithms can substantially decrease the noise in stochastically rendered images. Recent algorithms for defocus blur alone are both fast and accurate. However, motion blur is a considerably more complex type of camera effect, and as a consequence, current algorithms are either slow or too imprecise to use in high quality rendering. We extend previous work on real-time light field reconstruction for defocus blur to handle the case of simultaneous defocus and motion blur. By carefully introducing a few approximations, we derive a very efficient sheared reconstruction filter, which produces high quality images even for a low number of input samples. Our algorithm is temporally robust, and is about two orders of magnitude faster than previous work, making it suitable for both real-time rendering and as a post-processing pass for offline rendering.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Three-Dimensional Graphics and Realism&mdash display algorithms

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Guided Volume Editing based on Histogram Dissimilarity

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COMPUTER GRAPHICS FORUM 2015年第3期34卷 91-100页

作者： Karimov, A. Mistelbauer, G. Auzinger, T. Bruckner, S. Vienna Univ Technol Inst Comp Graph & Algorithms A-1040 Vienna Austria Univ Bergen Dept Informat N-5008 Bergen Norway

Segmentation of volumetric data is an important part of many analysis pipelines, but frequently requires manual inspection and correction. While plenty of volume editing techniques exist, it remains cumbersome and errorprone for the user to find and select appropriate regions for editing. We propose an approach to improve volume editing by detecting potential segmentation defects while considering the underlying structure of the object of interest. Our method is based on a novel histogram dissimilarity measure between individual regions, derived from structural information extracted from the initial segmentation. Based on this information, our interactive system guides the user towards potential defects, provides integrated tools for their inspection, and automatically generates suggestions for their resolution. We demonstrate that our approach can reduce interaction effort and supports the user in a comprehensive investigation for high-quality segmentations.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Picture/Image Generation&mdash display algorithms I.3.6 [Computer Graphics]: Methodology and Techniques&mdash Interaction techniques I.4.6 [Image Processing and Computer Vision]: Segmentation&mdash Edge and feature detection

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EFFICIENT display OF QUADRIC CSG MODELS

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COMPUTERS IN INDUSTRY 1992年第2期19卷 201-211页

作者： VANKLEIJ, R DELFT UNIV TECHNOL FAC TECH MATH & INFORMAT2628 BL DELFTNETHERLANDS

CSG (Constructive Solid Geometry) is a method for defining complex solid objects as a combination of simple primitives. This paper gives a short overview of modeling with CSG and of methods for generating shaded images of CSG models. An efficient scanline algorithm for CSG models with quadric primitives is presented, which gives reasonable display times on a general-purpose workstation. Some remarks on the performance on future workstations are made.

关键词： display algorithms CONSTRUCTIVE SOLID GEOMETRY QUADRICS SCANLINE algorithms

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BRDC: binary representation of displacement code for line

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COMPUTERS & GRAPHICS-UK 2002年第3期26卷 401-408页

作者： Miao, LF Liu, XG Peng, QS Bao, HJ Zhejiang Univ State Key Lab CAD&CG Hangzhou 310027 Peoples R China Zhejiang Normal Univ Dept Comp Sci Jinhua 321004 Peoples R China

In raster graphics, a line is displayed as a sequence of connected pixels that best approximate the line with minimum deviation. The displacement code of a line is a sequence of binary codes, each of which represents the displacement of a pixel on the line to its immediate predecessor pixel on the line. In fact, the displacement code records the entire process of drawing a line with successive pixels and it is deterministic for each specific line. In this paper, we study the important properties of the binary representation of displacement code, called BRDC, including calculation formula, periodicity, complement, decomposition etc. At last, we put forward an efficient adaptive multi-pixel line drawing algorithm based on exploited properties of BRDC, which demonstrates that BRDC is significant for designing efficient line drawing algorithms. (C) 2002 Elsevier Science Ltd. All rights reserved.

关键词： raster display devices line and curve generation display algorithms displacement code

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