|
Lighting and Occlusion in a Wave-Based FrameworkWe present novel methods to enhance Computer Generated Holography (CGH) by introducing a complex-valued wave-based occlusion handling method. This offers a very intuitive and efficient interface to introduce optical elements featuring physically-based light interaction exhibiting depth-of-field, diffraction, and glare effects. Furthermore, an efficient and flexible evaluation of lit objects on a full-parallax hologram leads to more convincing images. Previous illumination methods for CGH are not able to change the illumination settings of rendered holograms. In this paper we propose a novel method for real-time lighting of rendered holograms in order to change the appearance of a previously captured holographic scene. These functionalities are features of a bigger wavebased rendering framework which can be combined with 2D framebuffer graphics. We present an algorithm which uses graphics hardware to accelerate the rendering. Ziegler, R., Croci, S., Gross, M."Lighting and Occlusion in a Wave-Based Framework" EG 2008. |
|
A Bidirectional Light Field - Hologram TransformBest Paper Award and Best Student Paper Award Eurographics 2007 In this paper, we propose a novel framework to represent visual information. Extending the notion of conventional image-based rendering, our framework makes joint use of both light fields and holograms as complementary representations. We demonstrate how light fields can be transformed into holograms, and vice versa. By exploiting the advantages of either representation, our proposed dual representation and processing pipeline is able to overcome the limitations inherent to light fields and holograms alone. We show various examples from synthetic and real light fields to digital holograms demonstrating advantages of either representation, such as speckle-free images, ghosting-free images, aliasing-free recording, natural light recording, aperture-dependent effects and real-time rendering which can all be achieved using the same framework. Capturing holograms under white light illumination is one promising application for future work. Ziegler, R., Bucheli, S., Ahrenberg, L., Magnor, M., Gross, M."A Bidirectional Light Field - Hologram Transform" EG 2007. |
|
A Framework for Holographic Scene Representation and Image SynthesisTraditionally, graphics objects or scenes have been represented through geometry and appearance. Most often, geometry is described by primitives such as triangles, points, basis functions, and others, while appearance is encoded in texture maps. Due to the difficulty of representing some real-world objects, such as fur, hair, or trees, with traditional techniques, research has also focused on image based rendering usinglight-fields, lumigraphs, reflectance fields, sprites, and other models. In all these graphics representations the treatment of light is motivated through ray optics, and rendering involves projection and rasterization, or ray tracing. Ziegler, R., Kaufmann, P., Gross, M."A Framework for Holographic Scene Representation and Image Synthesis" To appear in IEEE TVCG 2007. Ziegler, R., Kaufmann, P., Gross, M."A Framework for Holographic Scene Representation and Image Synthesis" Sketch presented at SIGGRAPH 2006. |
|
Low-Cost Telepresence for Collaborative Virtual EnvironmentsWe present a novel low-cost method for visual communication and telepresence in a CAVETM-like environment, relying on 2D stereo-based video avatars. The system combines a selection of proven efficient algorithms and approximations in a unique way, resulting in a convincing stereoscopic real-time representation of a remote user acquired in a spatially immersive display. The system was designed to extend existing projection systems with acquisition capabilities requiring minimal hardware modifications and cost. Rhee, S.-M., Ziegler, R., Park, J., Naef, M., Gross, M., Kim, M.-H. "Low-Cost Telepresence for Collaborative Virtual Environments" To appear in TVCG January/February 2007. |
|
Adaptive Instant Displays: Continuously Calibrated Projections Using Per-Pixel Light ControlWe present a framework for achieving user-defined on-demand displays in setups containing bricks of movable cameras and DLP-projectors. A dynamic calibration procedure is introduced, which handles cameras and projectors in a unified way and allows continuous flexible setup changes, while seamless projection alignment and blending is performed simultaneously. For interaction, an intuitive laser pointer based technique is developed, which can be combined with real-time 3D information acquired from the scene. All these tasks can be performed concurrently with the display of a user-chosen application in a non-disturbing way. This is achieved by using an imperceptible structured light approach enabling pixel-based surface light control suited for a wide range of computer graphics and vision algorithms. To ensure scalability of light control in the same working space, multiple projectors are multiplexed. Cotting, D., Ziegler, R., Gross, M., Fuchs, H. "Adaptive Instant Displays: Continuously Calibrated Projections Using Per-Pixel Light Control" In Proceedings of Eurographics 2005. |
|
3D Reconstruction Using Labeled Image RegionsIn this paper we present a novel algorithm for reconstructing 3D scenes from a set of images. The user defines a set of polygonal regions with corresponding labels in each image using familiar 2D photo-editing tools. Our reconstruction algorithm computes the 3D model with maximum volume that is consistent with the set of regions in the input images. The algorithm is fast, uses only 2D intersection operations, and directly computes a polygonal model. We implemented a user-assisted system for 3D scene reconstruction and show results on scenes that are difficult or impossible to reconstruct with other methods. Ziegler, R., W. Matusik, H. Pfister, and L McMillan, "3D Reconstruction Using Labeled Image Regions." In Proceedings of Eurographics Symposium on Geometry Processing 2003. |
|
Image-Based 3D Photography using Opacity HullsWe have built a system for acquiring and displaying high quality graphical models of objects that are impossible to scan with traditional scanners. Our system can acquire highly specular and fuzzy materials, such as fur and feathers. The hardware set-up consists of a turntable, two plasma displays, an array of cameras, and a rotating array of directional lights. We use multi-background matting techniques to acquire alpha mattes of the object from multiple viewpoints. The alpha mattes are used to construct an opacity hull. The opacity hull is a new shape representation, defined as the visual hull of the object with view-dependent opacity. It enables visualization of complex object silhouettes and seamless blending of objects into new environments. Our system also supports relighting of objects with arbitrary appearance using surface reflectance fields, a purely image-based appearance representation. Our system is the first to acquire and render surface reflectance fields under varying illumination from arbitrary viewpoints. We have built three generations of digitizers with increasing sophistication. In this paper, we present our results from digitizing hundreds of models. Matusik, W., H. Pfister, A. Ngan, P. Beardsley, R. Ziegler, L. McMillan. "Image-based 3D Photography using Opacity Hulls." In Proceedings of SIGGRAPH 2002. |
|
Acquisition and Rendering of Transparent and Refractive ObjectsThis paper introduces a new image-based approach to capturing and modeling highly specular, transparent, or translucent objects. We have built a system for automatically acquiring high quality graphical models of objects that are extremely difficult to scan with traditional 3D scanners. The system consists of turntables, a set of cameras and lights, and monitors to project colored backdrops. We use multi-background matting techniques to acquire alpha and environment mattes of the object from multiple viewpoints. Using the alpha mattes we reconstruct an approximate 3D shape of the object. We use the environment mattes to compute a high-resolution surface reflectance field. We also acquire a low-resolution surface reflectance field using the overhead array of lights. Both surface reflectance fields are used to relight the objects and to place them into arbitrary environments. Our system is the first to acquire and render transparent and translucent 3D objects, such as a glass of beer, from arbitrary viewpoints under novel illumination. Matusik, W., H. Pfister, R. Ziegler, A. Ngan, L. McMillan, "Acquisition and Rendering of Transparent and Refractive Objects." In Proceedings of Eurographics Workshop on Rendering 2002. |
|
Cartoon Dioramas in MotionCartoon animations are traditionally seen on screen. On the other hand, static cartoon dioramas are commonly seen in shops and amusement parks. We present techniques to combine the two in limited cases. We illuminate static physical models with projectors. The images are generated with real time three dimensional computer graphics. We describe a system to demonstrate various visual effects such as non-photorealistic shading, apparent motion and virtual lighting on a toy-car model. Raskar, R.; Ziegler, R.; Willwacher, T., "Cartoon Dioramas in Motion",
International Symposium on Non-Photorealistic Animation and Rendering (NPAR),
June 2002 (NPAR
2002, TR2002-28) |
|
Direct Rotational Interaction With a Spherical ProjectionThis paper investigates a design for a new form of interactivity with information projected onto a spherical surface. This form of interaction is related to the direct rotation of the spherical surface itself. Traditional methods of computer interaction use a representative format, such as the movement of a mouse representing motion of a cursor on a flat screen. This representative interaction often becomes less obvious with a three dimensional object as there is often an exact view position required. The rotational interaction method developed provides a more direct physical connection with the data interaction upon a sphere by mimicking globe style rotational interaction. Design and implementation of the rotation interactivity are described in detail, including a discussion of the limitations involved. Kettner, S.; Madden, C.; Ziegler, R., "Direct Rotational Interaction With Spherical Projection", In Interaction: Systems, Practice and Theory 2004 (cooperation with ACM SIGCHI) |
