Volume 21, Number 3 (2013)
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Item Creating Finite Element Models of Facial Soft Tissue(Václav Skala - Union Agency, 2013) Warburton, Mark; Maddock, Steve; Skala, VáclavPhysically-based animation techniques enable more realistic and accurate animation to be created. Such approaches require the creation of a complex simulation model that, for computer graphics applications, can efficiently produce realistic-looking animations. We present a process to automatically create animatable nonconforming hexahedral finite element (FE) simulation models of facial soft tissue, including automatic computation of skin layers and element material properties, muscle properties and boundary conditions, making them immediately ready for simulation. Using the GPU, the detailed models can simulate complex gross and fine-scale behaviour, such as wrinkling. Our process can also be used to create a multi-layered FE model of any object (not just soft tissue).
Item Distributed VFX Architecture for SPH Simulation(Václav Skala - Union Agency, 2013) Morgenroth, Dieter; Weiskopf, Daniel; Eberhardt, Bernhard; Skala, VáclavWe propose an approach to simulating and rendering physically based fluid effects in a VFX production environment using a client/server architecture that is practical for distributed simulation resources and that can be seamlessly integrated into commercial 3D animation packages. The fluid simulation implements smoothed particle hydrodynamics (SPH). We extend the concept of surface particles by introducing blind particles that facilitate efficient direct raytracing of isosurfaces. We evaluate the performance of our approach with local simulation on CPUs and GPUs and distributed GPU simulation. We demonstrate the integration into the animation package 3ds Max and the VRay raytracer. The usability of the VFX production pipeline is assessed by a user study with VFX professionals and animation experts.Item Visual Parameter Exploration in GPU Shader Space(Václav Skala - Union Agency, 2013) Mindek, Peter; Bruckner, Stefan; Rautek, Peter; Gröller, M. Eduard; Skala, VáclavThe wide availability of high-performance GPUs has made the use of shader programs in visualization ubiquitous. Understanding shaders is a challenging task. Frequently it is difficult to mentally reconstruct the nature and types of transformations applied to the underlying data during the visualization process. We propose a method for the visual analysis of GPU shaders, which allows the flexible exploration and investigation of algorithms, parameters, and their effects. We introduce a method for extracting feature vectors composed of several attributes of the shader, as well as a direct manipulation interface for assigning semantics to them. The user interactively classifies pixels of images which are rendered with the investigated shader. The two resulting classes, a positive class and a negative one, are employed to steer the visualization. Based on this information, we can extract a wide variety of additional attributes and visualize their relation to this classification. Our system allows an interactive exploration of shader space and we demonstrate its utility for several different applications.Item Texture Mapping of Images with Arbitrary Contours(Václav Skala - Union Agency, 2013) Cherin, Nicolas; Cordier, Frederic; Melkemi, Mahmoud; Skala, VáclavDecaling is an intuitive paradigm for texture mapping in an analogy of attaching stickers on an object in the real world. This paradigm enables an artist to put decals directly on a 3D model after interactive manipulations such as modifying their positions, scales and orientations. In this paper, we present a novel method for multipleconstrained decaling. Given a region inside a texture together with a set of feature points in the region and a 3D model, our problem is to map the texture region onto the surface of the model in an intuitive manner, while satisfying the constrained imposed by a user-specified correspondence between a set of feature points in the region and the surface. We propose a solution for this problem. Our approach iteratively determines a portion of the mesh representing the surface while accordingly refining its parameterization, guided by the feature point correspondence.Item Rendering of Bézier Surfaces on Handheld Devices(Václav Skala - Union Agency, 2013) Concheiro, Raquel; Amor, Margarita; Padrón, Emilio J.; Gil, Marisa; Martorell, Xavier; Skala, VáclavBézier surfaces have been widely employed in the designing of complex scenes with high-quality results. Nevertheless, parametric surfaces cannot be directly rendered in the current GPUs of modern handheld devices. This work proposes a non-adaptive method for tessellating Bézier surfaces on a GPU without primitive generator, such as the GPUs implemented in handled devices. Our technique is based on the utilization of a parametric map of virtual vertices, and its operation can be adapted to the hardware resources available in the GPU by tuning a series of parameters. Additionally, an analysis of the most relevant hardware constraints in the graphics hardware of the current handheld devices has been carried out. As those constraints prevent interactive high-quality results from being achieved, even with our proposal, we present an algorithmic approach focused on the real-time rendering on future handheld devices.Item Screen Space Foam Rendering(Václav Skala - Union Agency, 2013) Akinci, Nadir; Dippel, Alexander; Akinci, Gizem; Teschner, Matthias; Skala, VáclavWe present a method for the efficient rendering of large scale particle-based foam data in screen space using a GPU based rendering pipeline. Our approach employs a multi-pass rendering technique to imitate some of the effects that are commonly accomplished by using expensive ray-tracing based methods. We demonstrate through different scenarios that our pipeline is able to produce convincing foam renderings for large scale scenarios and it has a significant performance advantage compared to using ray-casting techniques for rendering such particle data.Item VDR-AM: View-Dependent Representation of Articulated Models(Václav Skala - Union Agency, 2013) Claudio, Pio; Kim, Dohyeong; Kim, Tae-Joon; Yoon, Sung-eui; Skala, VáclavWe present a novel, View-Dependent Representation of Articulated Models (VDR-AM), and show its main benefits in the context of view-dependent rendering integrated with occlusion culling for large-scale crowd scenes. In order to provide varying resolutions on each animated, articulated model, we propose to use a cluster hierarchy in the VDR-AM for an articulated model. The cluster hierarchy serves as a dual representation for both view-dependent rendering and occlusion culling. For a high-performance view-dependent rendering and occlusion culling, we construct each cluster of the cluster hierarchy to contain a spatially coherent portion of the mesh that also has similar simplification errors. To achieve our goal, we present an error-aware clustering method for articulated models. We also identify a subset of animation poses that well represents the original pose data and perform the well-known quadrics-based simplification to efficiently compute our representation, while achieving a high quality simplification. At runtime, we choose a LOD cut from the cluster hierarchy given a user specified error bound in the screen space and render all the visible clusters in the LOD cut. We implement our method in GPU and achieve interactive performance (e.g., 40 frames per second) for large-scale crowd scenes that consist up to thousands of articulated models and 242 M triangles, without noticeable visual artifacts.
