Short Presentations

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https://diglib.eg.org/handle/10.2312/225

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3dml: A Language for 3D Interaction Techniques
(Eurographics Association, 2001) Figueroa, Pablo; Green, Mark; Hoover, H. James
We present 3dml, a markup language for 3D interaction techniques and virtual environment applications that involve non-traditional devices. 3dml has two main purposes: readability and rapid development. Designers can read 3dml-based representations of 3D interaction techniques, compare them, and understand them. 3dml can also be used as a front end for any VR toolkit, so designerswithout programming skills can create VR applications as 3dml documents that plug together interaction techniques, VR objects, and devices. This paper focuses on the language features and presentation scheme designed in our website (http://www.cs.ualberta.ca/~pfiguero/3dml).
Adaptive Progressive Vertex Tracing for Interactive Reflections
(Eurographics Association, 2001) Ullmann, Thomas; Schmidt, Alexander; Beier, Daniel; Bruderlin, Beat
This paper presents an approach for real-time rendering of physically accurate reflection effects in virtual environments. We apply a hybrid rendering of an OpenGL-generated scene, blended with correct reflection characteristics of selected scene objects. The core of the approach consists of a special type of ray tracing, the so-called vertex tracing. Real-time performance, even for complex CAD scenes, is achieved by progressive adaptive refinement, (derived from the geometry in object space) as well as by parallelization of the algorithm. A mesh-based load balancing yields a uniform distribution of the computing load in a heterogeneous network with resources with widely varying performance. The performance of the overall system is demonstrated using a truck interior in a Virtual Reality simulator.
Animating cuts with on-the-fly re-meshing
(Eurographics Association, 2001) Ganovelli, Fabio; O’Sullivan, C.
The problem of defining a model for deformable objects which allows the user to perform cuts is still open. Generally speaking, the reason is that such a task affects the connectivity and the topology of the mesh, while the assumption that they never change is the basis of most algorithms for both computation of deformation and collision detection. The drawback of approaching this problem as one of cutting based on re-meshing, is that the mesh exhibits a higher density where it has been cut than elsewhere. This paper proposes an on-the-fly tetrahedral simplification scheme to cope with such a fragmentation problem.
Animation of Facial Expressions by Physical Modeling
(Eurographics Association, 2001) Zhang, Yu; Prakash, Edmond C.; Sung, Eric
In this paper, we propose a physically-based 3D dynamic facial model based on anatomical knowledge for realistic facial expression animation. The facial model incorporates a physically-based approximation to facial skin tissue and a set of anatomically-motivated facial muscle actuators. The tissue model has multilayered mass-spring structure which approximates different types of facial tissue. Two kinds of biphasic springs, structural springs and shear springs, are included in our model to simulate nonlinear elastic behavior of the skin. Facial muscle models are presented to emulate facial muscle contraction. In the muscle model, two factors, the muscle force scaling factor and muscle strength factor provide us macro and micro control of the muscle influence respectively. Based on the facial anatomy, these contractile muscles are inserted at anatomically correct position within the dynamic skin model. Lagrangian mechanics governs the dynamics, dictating the deformation of facial surface in response to muscle forces. The dynamic facial animation algorithm runs at interactive rate with continuous 3D display on a graphics workstation.
Approximated Phong Shading by using the Euler Method
(Eurographics Association, 2001) Hast, Anders; Barrera, Tony; Bengtsson, Ewert
After almost three decades and several improvements, Gouraud shading is still more often used for interactive computer graphics than Phong shading. One of the main reasons for this is of course that Phong shading is computationally more expensive. Quadratic polynomial approximation techniques like Bishop’s method could reduce the amount of computation in the inner loop to just the double of what is done in Gouraud shading. By using Euler’s method we get another quadratic polynomial approximation technique which is just as fast in the inner loop, but it will also give correct intensities on the edges, which we will not get with Bishop’s method. By computing the maximum difference over a scan line between Gouraud shading and the proposed method, we could decide if Gouraud will suffice. It is also shown that linearly interpolated normals are normalized by a symmetric function. This means that we could reduce the amount of square roots by the half in Phong shading.
Approximated View Reconstruction Using Precomputed ID-Bitfields
(Eurographics Association, 2001) Meruvia Pastor, Oscar E.; Strothotte, Thomas
A technique is presented to construct arbitrary views of a model by using previously computed views. The technique is simple to implement, completely general for polygonal models and can be used within object hierarchies or scene graphs. During a preprocessing step images of a model are taken from different viewpoints. These images are saved using long bitfields (ID-bitfields) which encode the visibility information according to an array of the model’s primitives used as the base for the bitfield. These ID-bitfield encodings, together with the primitive array, are then used by a viewer which selects and joins them to provide an approximated (not conservative) reconstruction of the visible elements of the object for a new viewpoint. The technique implicitly performs occlusion culling, since a minimal set of visible polygons is the result of the reconstruction. Results show how interaction can be improved when working with high depth complexity models. Satisfactory reconstructions are achieved by taking as few as 25 images around an object. This paper suggests how the technique can be extended to other applications such as virtual walkthroughs and visualization of non-realistic images, and how graphics libraries and hardware could be enhanced by allowing the application to pass an ID-bitfield. Key words: view reconstruction, interactive display, visibility preprocessing, occlusion culling, polygon reduction.
Artist Driven Expressive Graphics
(Eurographics Association, 2001) Mason, Kaye; Carpendale, Sheelagh
Current methods in non-photorealistic graphics can place a heavy emphasis on the algorithm, as opposed to the artist. In this paper, we analyse these trends, and present a conceptual framework for putting control back in the hands of the artist. Combining ideas from non-photorealistic graphics and artificial intelligence, we present new methods of supporting alternative artistic styles. Details of our implementation of this model are described, as well as methods for interaction. Finally, we create a simulation under this framework, and show preliminary results.
Automatic Animated Face Modeling Using Multiview Video
(Eurographics Association, 2001) Wu, Fu-Che; Murphy, Chien-Chang Ho; Ouhyoung, Ming
An image-based 3-D modeling system is presented in this paper. Our modeling system consists of three main stages: camera calibration, depth estimation and 3-D geometry reconstruction. All of these steps are executed automatically. In the camera calibration stage, some patterns are used that help to determine the camera’s position in an environment. The camera’s intrinsic and external parameters are determined using epipolar geometry. After the camera parameters are determined, the camera’s location in each projected frame is determined. The depth for each pixel in a base image is estimated from the camera’s focus to the object’s surface by measuring the similarity between the base image and the neighboring images. The object’s 3-D geometry is reconstructed with texture from the base image using the depth information.
Collision Detection for Continuously Deforming Bodies
(Eurographics Association, 2001) Larsson, Thomas; Akenine-Möller, Tomas
Fast and accurate collision detection between geometric bodies is essential in application areas like virtual reality, animation, simulation, games and robotics. In this work, we address the collision detection problem in applications where deformable bodies are used, which change their overall shape every time step of the simulation. We propose and evaluate suitable bounding volume trees for deforming bodies that can be pre-built and then updated very efficiently during simulation. Several heuristics for updating the trees due to deformations are compared to each other. By combining a top-down and a bottom-up update strategy into a hybrid tree update method, promising results were achieved. Experiments show that our approach is four to five times faster than a previously leading method.
Complexity Reduction of Catmull-Clark/Loop Subdivision Surfaces
(Eurographics Association, 2001) Steenberg, Eskil
By applying a filter this algorithm can reduce the number of polygons generated by subdividing a mesh dynamically. This algorithm is designed especially for real-time engines where the geometrical complexity is critical. It also avoids edge cracks and is generally more efficient than a general-purpose polygon reduction algorithm.
Constructive Hypervolume Textures
(Eurographics Association, 2001) Schmitt, B.; Pasko, A.; Adzhiev, V.; Schlick, C.
The concept of solid texturing is extended in two directions: constructive modeling of space partitions for texturing and modeling of multidimensional textured objects called hypervolumes. A hypervolume is considered as a point set with attributes of both physical (density, temperature, etc.) and photometric (color, transparency, diffuse and specular reflections, etc.) nature. The point set geometry and attributes are modeled independently using real-valued scalar functions of several variables. Each real-valued function defining geometry or an attribute is evaluated in the given point by a procedure traversing a constructive tree structure with primitives in the leaves and operations in the nodes of the tree. This approach provides a framework for modeling, texturing and visualization of 3D solids, time- dependent and multidimensional objects in a completely uniform manner. We introduced a special modeling language and implemented software tools supporting the proposed approach. The concept of constructive hypervolume textures is independent of the geometry representation. We provide examples of textured Frep and BRep objects as illustrations.
CORBA Visualization Platform
(Eurographics Association, 2001) Benoist, Thierry; Hewitt, W. T.; John, Nigel W.
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Data driven motion transitions for interactive games
(Eurographics Association, 2001) Mizuguchi, Mark; Buchanan, John; Calvert, Tom
In 3D video games that employ human characters, a series of animations is required to display a character’s motion. The current approach is to use stored animation sequences, either motion captured or hand animated, and play them back as required. Unlike a sequence for film or video the motion needs to change according to the user’s interaction with the game. There are constant unpredictable transitions from one animation into another. This paper presents the design and analysis of a framework for supporting data driven transitions that have been pre-specified by animators. This approach frees the programmers from having to determine the details of each transition and gives control to the animators. This takes advantage of the animators’ skill at evaluating and tweaking the motion to produce better aesthetic results and lets the animators and programmers work in parallel.
Deformable Terrain Generation for Real-time Strategy Game
(Eurographics Association, 2001) Davison, Christopher; Tang, Wen
In this paper, we present a system that has the ability to deform terrain for Real-time Strategy Game with general PC hardware specifications. Various effects could be simulated in real-time such as raising and lowering the ground, creating a large chasm, or levelling the terrain. Effects such as ordering a unit to fire that then destroys part of a mountain could also be replicated. We present our implementations and techniques in using terrain deformation algorithms, Real-time Optimally Adapting Meshes, texture design and terrain generations. An analysis of the speed and memory usage of the system with respect to different PC hardware systems is also presented.
Fractal approximation of surfaces based on projected IFS attractors
(Eurographics Association, 2001) Guerin, Eric; Tosan, Eric; Baskurt, Atilla
A method for approximating smooth or rough surfaces defined in R3 is introduced. A fractal model called projected IFS model allows the extension of the iteration space to a barycentric space Rn2 by enriching the classical IFS model with a set of control points (m2 points). This flexible model has good fitting properties for recovering surfaces. The input for the model is single viewpoint range data defined on a fixed grid and also 2D grey-level images considered as surfaces. The model recovery is formulated as a non-linear fitting problem and resolved using a modified LEVENBERG-MARQUARDT minimization method. During the iterative fitting algorithm, all the parameters of the projected IFS model are adjusted simultaneously in order to minimize the overall distance between the models surface and the original data. The final model is very compact and gives satisfactory results on synthetic range data and real geological surfaces. The main applications are surface modeling, shape description and geometric surface compression.
Free-Form Deformation of Solid Models in CSR
(Eurographics Association, 2001) Hui, K. C.; Lai, C.F.
Existing free-form deformation (FFD) techniques deform an object by deforming the space enclosing the object. Points on the object are thus deformed relative to the undeformed space (or world space). The deformed object is visualized by sampling points on the object surfaces, or by approximating the object with a polyhedral model. This provides good visual effect for the deformed objects. However, the deformed solid is represented in terms of the lattice of the FFD and the undeformed solid. There is no precise explicit representation of the deformed object so that existing solid modeling techniques, such as Boolean operations, on the deformed object may not be applied. This paper is concerned with the techniques of applying free-form deformation on solid models represented by the Constructive Shell Representation (CSR). By applying free-form deformation on the surface points of the trunctets of a CSR object so that the vertices and the quadric patch polynomial of the trunctets are changed, the shape of the object can be modified. This technique can be used to deform globally smooth solid models or general solid models with sharp edges. The deformation can be applied either globally or locally. Techniques for the deformation are discussed in detail. Experiments are conducted and the results are also presented.
Game Based Interfaces
(Eurographics Association, 2001) Diener, Holger; Schumacher, Hagen
Complex menu and dialog structures prevent users from working intuitively with standard applications. In this paper, a new kind of user interface is suggested based on concepts of computer games. Defining a new structure for the functionality of an application will simplify users adjustment to new applications and will improve their everyday work. Usability tests based on eye tracking devices are described to verify the correctness of this game based interface approach. In addition, other game based concepts are introduced, which can be transferred to standard applications to improve the usability.
Gaze-Contingent Level Of Detail Rendering
(Eurographics Association, 2001) Murphy, Hunter; Duchowski, Andrew T.
The contributions of this paper are the development and evaluation of a nonisotropic model-based Level Of Detail (LOD) rendering technique for gaze-contingent viewing of multiresolution meshes. A high resolution portion of the model is rendered at the eye-tracked Point Of Regard (POR). A method is given for converting a closed polygonal mesh to a nonisotropic LOD representation suitable for gaze-contingent viewing. Based on a theoretical model of visual acuity, a three-dimensional spatial degradation function is obtained from human subject experiments in an attempt to render imperceptibly degraded geometric objects. Unlike previous LOD approaches, our resolution degradation method is based on the measurement of visual angle in world coordinates and is applied directly to object geometries prior to rendering. The gaze-contingent technique is evaluated in a Virtual Reality (VR) system integrated with a binocular eye tracker. To our knowledge, this is the first example of a binocular eye-tracked VR system used to evaluate a gaze-contingent modeling technique. Results are reported in terms of rendering performance, indicating an overall 4-fold average frame rate improvement during gaze-contingent viewing. Frame rate improvement ranged from a factor of at least 2, up to a 15-fold gain in performance over full resolution display, varying with the model complexity and the instantaneous direction of the viewer’s gaze.
HYPER MASK – Projecting a Virtual Face onto a Moving Real Object
(Eurographics Association, 2001) Morishima, Shigeo; Yotsukura, T.; Nielsen, F.; Binsted, K.; Pinhanez, C.
HYPERMASK is a system which projects an animated face onto a physical mask, worn by an actor. As the mask moves within a prescribed area, its position and orientation are detected by a camera, and the projected image changes with respect to the viewpoint of the audience. The lips of the projected face are automatically synthesized in real time with the voice of the actor, who also controls the facial expressions. As a theatrical tool, HYPERMASK enables a new style of storytelling. As a prototype system, we propose to put a self-contained HYPERMASK system in a trolley (disguised as a linen cart), so that it projects onto the mask worn by the actor pushing the trolley.
Improved Rendering with Dégradé
(Eurographics Association, 2001) Boyer, Vincent; Sobczyk, Dominique; Bourdin, Jean-Jacques
In most paintboxes drawing (and filling) the picture and render the picture are two different steps and tools. Dégradé presents an efficient filling rendering tool: an efficient collection of effect filling. In Dégradé the renderer is included in the drawing process. This method enhance the renderer possibilities and the graphic designer work.

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