EG2014 - Short Papers

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https://diglib.eg.org/handle/10.2312/7706

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Unsupervised Three-dimensional Reconstruction of Small Rocks from a Single Two-dimensional Image
(The Eurographics Association, 2014) Gilardi, Marco; Watten, Phil L.; Newbury, Paul; Eric Galin and Michael Wand
Surfaces covered with pebbles and small rocks can often be found in nature or in human-shaped environments. Generating an accurate three-dimensional model of these kind of surfaces from a reference image can be challenging, especially if one wants to be able to animate each pebble individually. To undertake this kind of task manually is time consuming and impossible to achieve in dynamic terrains animations. The method described in this paper allows unsupervised automatic generation of three-dimensional textured rocks from a two-dimensional image aiming to closely match the original image as much as possible.
Regional Time Stepping for SPH
(The Eurographics Association, 2014) Goswami, Prashant; Batty, Christopher; Eric Galin and Michael Wand
This paper presents novel and efficient strategies to spatially adapt the amount of computational effort applied based on the local dynamics of a free surface flow, for classic weakly compressible SPH (WCSPH). Using a convenient and readily parallelizable block-based approach, different regions of the fluid are assigned differing time steps and solved at different rates to minimize computational cost. We demonstrate that our approach can achieve about two times speed-up over the standard method even in highly dynamic scenes.
Post-Tessellation Geometry Caches
(The Eurographics Association, 2014) Sathe, Rahul; Foley, Tim; Salvi, Marco; Eric Galin and Michael Wand
Current 3D rendering architectures support adaptive tessellation of patches, allowing for increased geometric detail. Patches are specified independently, giving the implementation freedom to exploit parallel execution. However, this independence leads to redundant shading computations at patch corners and along edges. In this paper, we present post-tessellation geometry caches, the edge cache and corner cache, that can reduce redundant shading along patch edges and corners, respectively. We demonstrate the two caches in a software-simulated D3D11 rendering pipeline, and show that for current tessellation workloads our approach saves up to 37% of post-tessellation vertex shading using caches with as few as 8 entries.
Depth Sensor-Based Realtime Tumor Tracking for Accurate Radiation Therapy
(The Eurographics Association, 2014) Nutti, Björn; Kronander, Åsa; Nilsing, Mattias; Maad, Kristofer; Svensson, Cristina; Li, Hao; Eric Galin and Michael Wand
We present an image guided radiation therapy (IGRT) system for tracking tumors in realtime based on continuous structured light imaging. While an accurate positioning of the radiation isocenter to pre-imaged cancer cells is critical to minimize the risk of damaging healthy tissues, patients undergo involuntary motions such as breathing or unpredictable gestures during treatment. Moreover, multiple sessions are typically necessary and repositioning the patient accurately can be difficult. Our approach consists of determining the tumor position by densely tracking the deformation of a stream of 3D scans using a realtime variant of a state-of-the-art non-rigid registration algorithm and an FEM simulation on the interior body. We use interactive reprojection for visual guidance to adjust the posture of the patient and couch position, depending on the tumor location. Compared to existing techniques, our method uniquely estimates tumor deviations under body deformations. Our pipeline has been successfully commercialized as part of the C-RAD AB CatalystTM product line and is already deployed in a number of hospitals.
A User Study: Is the Advection Step in Shallow Water Equations Really Necessary?
(The Eurographics Association, 2014) Kellomäki, Timo; Saari, Timo; Eric Galin and Michael Wand
Heightfield methods, such as the pipe method and shallow water equations (SWE), have often been used to simulate large areas of water. Of these, the SWE are often preferred due to being more realistic, but they are also more complex and demand more computational resources than the pipe method. These two methods were presented to over 40 subjects in both a gaming and a video context to see whether they report noticing the advantages of SWE compared to the pipe method. No significant differences were observed in any of the categories measured (hedonic valence, flow, spatial presence, realism). Therefore, at least considering using the pipe method instead of the SWE is recommended. Also, varying the time step between 5 and 20 ms did not affect the user experience.
Merging Live and pre-Captured Data to support Full 3D Head Reconstruction for Telepresence
(The Eurographics Association, 2014) Fleury, Cedric; Popa, Tiberiu; Cham, Tat Jen; Fuchs, Henry; Eric Galin and Michael Wand
This paper proposes a 3D head reconstruction method for low cost 3D telepresence systems that uses only a single consumer level hybrid sensor (color+depth) located in front of the users. Our method fuses the real-time, noisy and incomplete output of a hybrid sensor with a set of static, high-resolution textured models acquired in a calibration phase. A complete and fully textured 3D model of the users head can thus be reconstructed in real-time, accurately preserving the facial expression of the user. The main features of our method are a mesh interpolation and a fusion of a static and a dynamic textures to combine respectively a better resolution and the dynamic features of the face.
Unified Skeletal Animation Reconstruction with Multiple Kinects
(The Eurographics Association, 2014) Ahmed, Naveed; Eric Galin and Michael Wand
We present a new method for reconstructing a unified skeletal animation with multiple Kinects. Our method is able to reconstruct the unified skeletal animation from Kinect data over 360 degrees. We make use of all three streams: RGB, depth and skeleton, along with the joint tracking confidence state from Microsoft Kinect SDK to find the correctly oriented skeletons and merge them together to get a uniform animation. Our method is easy to implement and provides a simple solution of creating a 360 degree plausible unified skeletal animation that would not be possible to capture with a single Kinect due to occlusions, tracking failures, and field of view constraints.
Combining Inertial Navigation and ICP for Real-time 3D Surface Reconstruction
(The Eurographics Association, 2014) Nießner, Matthias; Dai, Angela; Fisher, Matthew; Eric Galin and Michael Wand
We present a novel method to improve the robustness of real-time 3D surface reconstruction by incorporating inertial sensor data when determining inter-frame alignment. With commodity inertial sensors, we can significantly reduce the number of iterative closest point (ICP) iterations required per frame. Our system is also able to determine when ICP tracking becomes unreliable and use inertial navigation to correctly recover tracking, even after significant time has elapsed. This enables less experienced users to more quickly acquire 3D scans. We apply our framework to several different surface reconstruction tasks and demonstrate that enabling inertial navigation allows us to reconstruct scenes more quickly and recover from situations where reconstructing without IMU data produces very poor results.
HDR Reconstruction for Alternating Gain (ISO) Sensor Readout
(The Eurographics Association, 2014) Hajisharif, Saghi; Kronander, Joel; Unger, Jonas; Eric Galin and Michael Wand
Modern image sensors are becoming more and more flexible in the way an image is captured. In this paper, we focus on sensors that allow the per pixel gain to be varied over the sensor and develop a new technique for efficient and accurate reconstruction of high dynamic range (HDR) images based on such input data. Our method estimates the radiant power at each output pixel using a sampling operation which performs color interpolation, re-sampling, noise reduction and HDR-reconstruction in a single step. The reconstruction filter uses a sensor noise model to weight the input pixel samples according to their variances. Our algorithm works in only a small spatial neighbourhood around each pixel and lends itself to efficient implementation in hardware. To demonstrate the utility of our approach we show example HDR-images reconstructed from raw sensor data captured using off-the shelf consumer hardware which allows for two different gain settings for different rows in the same image. To analyse the accuracy of the algorithm, we also use synthetic images from a camera simulation software.
Deferred Shading for Order-Independent Transparency
(The Eurographics Association, 2014) Hillesland, Karl E.; Bilodeau, Bill; Thibieroz, Nicolas; Eric Galin and Michael Wand
Rendering many layers of transparency presents difficult challenges with respect to performance. Most previous work focused on the sorting problem, paying the full shading cost for all fragments. We present a method that defers shading until fragments can be classified as less important to the final pixel color, allowing us to switch to a lower-cost, approximate shading function. We apply this idea to TressFX, which is a state-of-the-art hair rendering technique used in video game production. For hair rendering, we switched to low-quality shading in all but the front eight fragments per pixel. This gave us a 75% speedup without noticeable loss in visual quality.
A Tone Reproduction Operator for All Luminance Ranges Considering Human Color Perception
(The Eurographics Association, 2014) Mikamo, Michihiro; Raytchev, Bisser; Tamaki, Toru; Kaneda, Kazufumi; Eric Galin and Michael Wand
In this paper, we present a novel tone reproduction operator that is able to handle the color shift that occurs in photopic, mesopic, and scotopic vision, using a model based on a two-stage model of human color vision and psychophysical data obtained from measurements of human color perception. Since conventional methods are limited to generating images under a certain visual condition, it is difficult to apply just one operator to deal with scenes with continuous change within a wide luminance range, such as various scenes in movies. To overcome this problem, we have developed a model based on psychophysical data involving wavelength discrimination within a wide luminance range, which provides us with clues about the change of color perception. That is, the spectral sensitivity shifts toward the short wavelengths and decreases according to the adaptation light levels. By integrating the wavelength discrimination into our model, the proposed operator enables us to compute the transition of color perception under a wide range of viewing conditions.
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.
CSG Feature Trees from Engineering Sketches of Polyhedral Shapes
(The Eurographics Association, 2014) Plumed, Raquel; Company, Pedro; Varley, Peter A. C.; Martin, Ralph R.; Eric Galin and Michael Wand
We give a method to obtain a 3D CSG model from a 2D engineering wireframe sketch which depicts a polyhedral shape. The method finds a CSG feature tree compatible with a reverse design history of a 2D line-drawing obtained by vectorising the sketch. The process used seeks the CSG feature tree recursively, combining all design or manufacturing features embedded in the sketch, proceeding in reverse order from the most detailed features to the blank.
Data Driven Assembly of Procedurally Modeled Facilities
(The Eurographics Association, 2014) Bishop, M. Scott; Ferrer, Josè; Max, Nelson; Eric Galin and Michael Wand
We present a method to arrange components of industrial facilities in a constrained site footprint. We use a probabilistic graphical model of industrial sites and existing procedural modeling methods to automate the assembly and 3D modeling of wastewater treatment plants. A knowledge engineered approach produces a combination of components that inherently contains domain specific information like process dependencies and facility size. The inferred combination is laid out using mathematical optimization or via a physics-based simulation resulting in an arrangement that respects the industrial process and design plausibility.
Information-Guided Transfer Function Refinement
(The Eurographics Association, 2014) Luo, Shengzhou; Dingliana, John; Eric Galin and Michael Wand
This paper examines the methods for exploring volume data by optimization of visualization parameters. The size and complexity of the parameter space controlling the rendering process makes it challenging to generate an informative rendering. In particular, the specification of the transfer function (which is a mapping from data values to visual properties) is frequently a time-consuming and unintuitive task. We propose an information theory based approach to optimize the transfer function based on the intensity distribution of the volume data set and the ability for users to specify priority areas of importance in the resulting image in a simple and intuitive way. This optimization approach reduces the occlusion in the resulting images, and thus improves the perception of structures.
Towards Understanding Beautiful Things: A Computational Approach for the Study of Color Modulation in Visual Art
(The Eurographics Association, 2014) Agahchen, Anissa; Albu, Alexandra Branzan; Eric Galin and Michael Wand
This paper is a guided attempt at analyzing the aesthetics of color from the perspective of color theory. Our guides are the works of Johannes Itten, one of the most influential theorists of color aesthetics. We focus on one specific aspect of color usage in visual art, namely color modulation. To this purpose, we introduce the color palette, a novel 3D visualization of the chromatic information of an image in the HSL space. Moreover, we propose a set of simple descriptors for evaluating color modulation. Our approach is demonstrated on two case studies, which show that our measures on modulation are consistent with Itten s color theory. Ongoing work involves a thorough experimental exploration of the proposed color palette and modulation descriptors, in terms of their ability to discriminate between different artists and painting styles.

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