Short Presentations 2005

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https://diglib.eg.org/handle/10.2312/250

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Progressive Cartesian Inequality Constraints for the Inverse Kinematic Control of Articulated Chains
(The Eurographics Association, 2005) Peinado, Manuel; Boulic, Ronan; Callennec, Benoit Le; Meziat, D.; John Dingliana and Fabio Ganovelli
We propose an Inverse Kinematic Control architecture capable of handling tasks that are expressed in terms of inequality constraints in the Cartesian space. These inequality constraints are progressive in the sense that their influence manifests itself in a zone of finite thickness by damping the progression toward the strict limit of the constraint. We show how to enforce this family of constraints in a two stage process with our prioritized IK sheme. Various examples highlight the potential of this approach for managing complex articulated chains in cluttered environments where obstacles are modelled with this type of constraints.
Constriction Computation using Surface Curvature
(The Eurographics Association, 2005) Hétroy, F.; John Dingliana and Fabio Ganovelli
This paper provides a curvature-based algorithm to compute locally shortest geodesics on closed triangulated surfaces. These curves, which are called "constrictions", are useful for shape segmentation. The key idea of the algorithm is that constrictions are almost plane curves; it first finds well-located simple, plane, closed curves, and then slides them along the surface until a shortest geodesic is reached. An initial curve is defined as a connected component of the intersection between the surface and a plane going through an initial vertex. Initial vertices and planes are determined using approximations of surface curvature.
Perception-Based Rendering: Eyes Wide Bleached
(The Eurographics Association, 2005) Gutierrez, Diego; Anson, Oscar; Munoz, Adolfo; Seron, Francisco J.; John Dingliana and Fabio Ganovelli
Perception issues are a key factor in rendering Vision-Realistic images. This paper develops a novel spectral sensitive model of the Human Visual System (HVS) in order to simulate the bleaching effect in retinal photopigments. First, the Stiles-Crawford effect is taken into account to determine the pupil size of the adapted eye and to compute the directional sensitivity of the photoreceptors in the retina. After that, the percentage of bleached pigment based on the incident retinal illuminance is calculated to simulate the loss of spectral sensitivity of the human observer seeing the scene.
Predicting Natural Hair Shapes by Solving the Statics of Flexible Rods
(The Eurographics Association, 2005) Bertails, Florence; Audoly, Basile; Querleux, Bernard; Leroy, Frédéric; Lévêque, Jean-Luc; Cani, Marie-Paule; John Dingliana and Fabio Ganovelli
This paper presents a new physically-based method for predicting natural hairstyles in the presence of gravity and collisions. The method is based upon a mechanically accurate model for static elastic rods (Kirchhoff model), which accounts for the natural curliness of hair, as well as for hair ellipticity. The equilibrium shape is computed in a stable and easy way by energy minimization. This yields various typical hair configurations that can be observed in the real world, such as ringlets. As our results show, the method can generate different hair types with a very few input parameters, and perform virtual hairdressing operations such as wetting, cutting and drying hair.
Efficient, Physically Plausible Finite Elements
(The Eurographics Association, 2005) Nesme, Matthieu; Payan, Yohan; Faure, François; John Dingliana and Fabio Ganovelli
This paper discusses FEM-based simulations of soft bodies in terms of speed and robustness. To be physically plausible, three fundamental laws must be respected: rotational invariance, Newton's law and Euler's law. We show that precomputed strain-displacement matrices generate nonphysical torques which can lead to visual artifacts. We then derive the fastest FEM-based method meeting our criteria of plausibility and robustness and discuss their limitations.
Real-time Upper Body 3D Pose Estimation from a Single Uncalibrated Camera
(The Eurographics Association, 2005) Micilotta, Antonio Salvatore; Ong, Eng Jon; Bowden, Richard; John Dingliana and Fabio Ganovelli
In this paper we introduce a real-time steering controller ensuring the reach of a (possible mobile) target position and orientation, without requiring to build/update the full trajectory to that target. We name it the funnelling control. The final orientation is achieved through the continuous adjustment of the heading direction. This control mode is proactive in the sense that it anticipates the success/failure of the reach and adjusts the desired speed accordingly. Both features rely on an heterogeneously sampled table of radial-tangential seek angles obtained when the controller reaches a desired position target without prescribed orientation. By construction, the control update has a constant computing cost, even with variable target characteristics. Its low update cost makes it particularly suited for controlling a large number of mobile entities in real-time. The present exposition is made for an obstacle-free context.This paper outlines a method of estimating the 3D pose of the upper human body from a single uncalibrated camera. The objective application lies in 3D Human Computer Interaction where hand depth information offers extended functionality when interacting with a 3D virtual environment, but it is equally suitable to animation and motion capture. A database of 3D body configurations is built from a variety of human movements using motion capture data. A hierarchical structure consisting of three subsidiary databases, namely the frontal-view Hand Position (top-level), Silhouette and Edge Map Databases, are pre-extracted from the 3D body configuration database. Using this hierarchy, subsets of the subsidiary databases are then matched to the subject in real-time. The examples of the subsidiary databases that yield the highest matching score are used to extract the corresponding 3D configuration from the motion capture data, thereby estimating the upper body 3D pose.
A Visual Quality Prediction Model for 3D Texture
(The Eurographics Association, 2005) Cheng, Irene; Boulanger, Pierre; John Dingliana and Fabio Ganovelli
Online bandwidth limitations and fluctuations impose a major challenge in estimating the amount of data to transmit in a given time period. Over or under estimation of bandwidth can jeopardize the visual fidelity of the transmitted and related multimedia data. We propose a Visual Quality Prediction (VQP) model which supports an adaptive fragmented texture transmission approach taking bandwidth fluctuations into consideration, and adjusts the data size (and thus quality) of the next block of texture data to be transmitted. The transmission depends on a set of predictors used to optimize an overall best effort visual quality.
Scalar Tagged PN Triangles
(The Eurographics Association, 2005) Boubekeur, Tamy; Reuter, Patrick; Schlick, Christophe; John Dingliana and Fabio Ganovelli
This paper presents a new technique to convert a coarse polygonal geometric model into a smooth surface interpolating the mesh vertices, by improving the principle proposed by Vlachos et al. in their "Curved PN-Triangles". The key idea is to assign to each mesh vertex, a set of three scalar tags that act as shape controllers. These scalar tags (called sharpness, bias, and tension) are used to compute a procedural displacement map that enriches the geometry, and a procedural normal map that enriches the shading. The resulting technique offers two majors features: First, it can be applied on meshes of arbitrary topology while always generating surfaces with consistent behaviors across edge and vertex boundaries, second, it only involves operations that are purely local to each polygon, which means that it is very well suited for hardware implementations.
Real-Time Rendering of Cloudy Natural Phenomena with Hierarchical Depth Impostors
(The Eurographics Association, 2005) Ummenhoffer, Tamás; Szirmay-Kalos, László; John Dingliana and Fabio Ganovelli
This paper presents a real-time method to realistically render dynamic participating media under changing lighting conditions. In order to cope with performance requirements, the volume is built of instances of particle blocks. The simulation and rendering happen on two levels, on the block level and on the volume level. On the volume level blocks are replaced by depth impostors, which allows for very fast recalculation of the cloud illumination. Including depth information into block impostors our technique also eliminates billboard clipping artifacts when the participating medium contains objects. The proposed method can render swirling clouds and smoke on high frame rates, and can be used in real-time applications.
A Sharpness Dependent Approach to 3D Polygon Mesh Hole Filling
(The Eurographics Association, 2005) Chen, Chun-Yen; Cheng, Kuo-Young; Liao, H.Y. Mark; John Dingliana and Fabio Ganovelli
A sharpness dependent hole filling approach is proposed in this paper. The proposed method can fill the hole of a mesh-based model and recover its sharp feature located at the hole area. Interpolation based on radial basis function is applied to create a smooth implicit surface and this surface can approximate the shape of the missed data. Then, a regularized marching tetrahedral algorithm is adopted to triangulate the above implicit surface and to produce a polygonal hole patch. A repaired mesh model is obtained by stitching the hole patch and the hole boundary of the original model. Finally, a feature enhancement process is applied if there exists a sharp feature on the hole boundary of the original model. The introduction of a sharpness dependent filter enhances the sharp feature of a hole-filled model. Experiment results show that our approach can produce excellent reparation results especially for recovering sharp feature.
Real-Time Marching Cubes on the Vertex Shader
(The Eurographics Association, 2005) Goetz, Frank; Junklewitz, Theodor; Domik, Gitta; John Dingliana and Fabio Ganovelli
In this paper we propose a new approach for visualizing volumetric datasets by their isosurfaces. For an interactive isosurface reconstruction an optimized version of the well-known marching cubes algorithm is used. We extend the original algorithm by an additional vertex shader program. Contrary to other hardware-accelerated solutions our program is not based on a tetrahedral algorithm and thus the implementation for structured grids is more effective. Furthermore, surfaces of time-varying datasets at distinguished threshold values can be extracted in real-time.
Preface
(The Eurographics Association, 2005) -; John Dingliana and Fabio Ganovelli
Preface and Table of Contents
Carving, Painting, and Printing with a Pen Tablet
(The Eurographics Association, 2005) Mizuno, Shinji; Kobayashi, Daigo; Okada, Minoru; Toriwaki, Junichiro; Yamamoto, Shinji; John Dingliana and Fabio Ganovelli
We discuss on an interactive CG system with a pressure sensitive pen tablet. This system is based on the virtual sculpting and printing method which are simulations of real sculpting and woodblock printing. In the sculpting process, the user operates virtual chisels with a pen to carve a virtual wooden object which has a 3D shape. The user can control the carving depth and the carving angle to the surface of the object with the pressure applied to the pen. In the painting process, the user paints ink with a pen on a 3D virtual sculpture created in the sculpting process. The painting result is determined by the surface shape of the sculpture and the pressure to the pen. In the printing process, a pen is used to operate a Japanese printing squeegee, Baren. The user can control the thickness of the print by changing the thickness of ink on the virtual woodblock and the pressure of printing operation.
Walking with Pens
(The Eurographics Association, 2005) Kolhoff, Philipp; Preuß, Jacqueline; Loviscach, Jörn; John Dingliana and Fabio Ganovelli
Believable 3D animation of walking or running characters still requires complex motion capture technology or extensive skills in manual keyframing. We present an inexpensive, yet natural input method: The user walks on a digital graphics tablet, striding over the surface with two pens in his or her hands, where each pen represents one leg. This technique leverages the popular graphics tablets that can track two drawing tools at the same time. We implemented recording software and a plug-in to use the data in off-the-shelf 3D animation software.
Improving the Experience of Scenes with a Large Field of View using Shift Lens Perspective
(The Eurographics Association, 2005) Hoeben, Aldo; Stappers, Pieter Jan; John Dingliana and Fabio Ganovelli
In interactive computer graphics such as games and interactive panoramic photos, users are often presented a view with a larger field of view than would correspond to the distance to and size of the screen on which the graphics are viewed. This makes looking at the scene a less claustrophobic experience, showing more of the environment than that which is strictly ahead. In many applications however, where the goal is to get a sense of presence and ambiance of the depicted scene, the large field of view distracts the observer with extreme converging lines when looking up or down. Even though these converging lines are perspectively correct, the resulting image does not match the way we normally perceive the world around us. In this paper we discuss modifying the perspective to reduce the distortions caused by the large field of view, to enhance the experience of these scenes.
Image Reconstruction Invariant to Relighting
(The Eurographics Association, 2005) Georgiev, Todor; John Dingliana and Fabio Ganovelli
This paper describes an improvement to the Poisson image editing method for seamless cloning. Our approach is based on minimizing an energy expression invariant to relighting. The improved method reconstructs seamlessly the selected region, matching both pixel values and texture contrast of the surrounding area, while previous algorithms matched pixel values only. Our algorithm solves a deeper problem: It performs reconstruction in terms of the internal working mechanisms of human visual system. Retinex-type effects of adaptation are built into the structure of the mathematical model, producing results that change covariantly with lighting.
Proactive Steering Toward Oriented Targets
(The Eurographics Association, 2005) Boulic, Ronan; John Dingliana and Fabio Ganovelli
In this paper we introduce a real-time steering controller ensuring the reach of a (possible mobile) target position and orientation, without requiring to build/update the full trajectory to that target. We name it the funnelling control. The final orientation is achieved through the continuous adjustment of the heading direction. This control mode is proactive in the sense that it anticipates the success/failure of the reach and adjusts the desired speed accordingly. Both features rely on an heterogeneously sampled table of radial-tangential seek angles obtained when the controller reaches a desired position target without prescribed orientation. By construction, the control update has a constant computing cost, even with variable target characteristics. Its low update cost makes it particularly suited for controlling a large number of mobile entities in real-time. The present exposition is made for an obstacle-free context.
Leaf Cluster Impostors for Tree Rendering with Parallax
(The Eurographics Association, 2005) Garcia, Ismael; Sbert, Mateu; Szirmay-Kalos, László; John Dingliana and Fabio Ganovelli
This paper presents a simple method to render complex trees on high frame rates while maintaining parallax effects. Based on the recognition that a planar impostor is accurate if the represented polygon is in its plane, we find an impostor for each of those groups of tree leaves that lie approximately in the same plane. The groups are built automatically by a clustering algorithm. Unlike billboards, these impostors are not rotated when the camera moves, thus the expected parallax effects are provided. On the other hand, clustering allows the replacement of a large number of leaves by a single semi-transparent quadrilateral, which improves rendering time considerably. Our impostors well represent the tree from any direction and provide accurate depth values, thus the method is also good for shadow computation.
Estimating Mobile Memory Requirements and Rendering Time for Remote Execution of the Graphics Pipeline
(The Eurographics Association, 2005) Banerjee, Kutty; Wu, Fan; Agu, Emmanuel; John Dingliana and Fabio Ganovelli
Mobile devices have limited processing power, memory and battery power. Remote execution, wherein part or entire graphics pipeline is offloaded to a powerful surrogate server, is an attractive solution for low end mobile devices such as PDAs and cell phones that lack floating point units or GPUs. We have found that remote execution of floating-point-intensive pipeline stages such as transform and geometry operations can produce speedups of up to 10 times for a low-end mobile device. We introduce generalized pipeline-splitting, a paradigm whereby 15 sub-stages of the graphics pipeline are instrumented with networking code such that they can run either on a mobile client or a surrogate server. To validate our concepts, we create Remote Mesa (RMesa). As a foundation for deciding which stages of the pipeline would benefit from remote execution, this paper presents analytical models for the overall rendering time, memory requirements and roundtrip network delay incurred by RMesa.
Facial Motion Cloning Using Global Shape Deformation
(The Eurographics Association, 2005) Fratarcangeli, Marco; Schaerf, Marco; John Dingliana and Fabio Ganovelli
We present a novel Facial Motion Cloning method relying on the combination of the radial basis functions (RBF) based scattered data interpolation with the encoding capabilities of the MPEG-4 Facial and Body Animation (FBA) international standard. Beside from an initial manual selection of feature points, our method works fully automatically without user interaction. The produced talking head is able to perform generic face animation which is stored in a MPEG-4 FBA data stream.

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