Using vanishing points for camera calibration and coarse 3D reconstruction from a single image

In this paper, we show how to calibrate a camera and to recover the geometry and the photometry (textures) of objects from a single image. The aim of this work is to make it possible walkthrough and augment reality in a 3D model reconstructed from a single image. The calibration step does not need any calibration target and makes only four assumptions: (1) the single image contains at least two vanishing points, (2) the length (in 3D space) of one line segment (for determining the translation vector) in the image is known, (3) the principle point is the center of the image, and (4) the aspect ratio is fixed by the user. Each vanishing point is determined from a set of parallel lines. These vanishing points help determine a 3D world coordinate system R _o. After having computed the focal length, the rotation matrix and the translation vector are evaluated in turn for describing the rigid motion between R _o and the camera coordinate system R _c. Next, the reconstruction step consists in placing, rotating, scaling, and translating a rectangular 3D box that must fit at best with the potential objects within the scene as seen through the single image. With each face of a rectangular box, a texture that may contain holes due to invisible parts of certain objects is assigned. We show how the textures are extracted and how these holes are located and filled. Our method has been applied to various real images (pictures scanned from books, photographs) and synthetic images.     

Edge-preserving texture filtering for real-time rendering

Texture filtering is essential in enhancing the visual quality of real-time rendering. Conventional schemes do not consider the characteristics of texture content, thus the sharpness of edges in texture images cannot be retained. This paper proposes a novel texture-filtering algorithm, which consists of edge-preserving interpolation and edge-preserving MIP-map prefiltering. The memory bandwidth requirement is kept the same as in conventional schemes by dynamically adjusting the interpolation kernel. Hardware implementation is also provided to show the real-time processing capability. Published online: 28 January 2003     

A method for generating pavement textures using the square packing technique

Published online: 2 October 2001     

The synthesis of rust in seawater

Computer graphics researchers have recently revealed that the presence of imperfections is an essential part of the illusion of photorealism. An improved model to simulate the rust development of ferrous metals in seawater is proposed. The tide and the current, under the gravity of the sun and the moon, affect the stability of the environment at the bottom of the ocean. A simple current model is employed to elucidate the periodic transition of currents in the ocean. L-systems, coupled with the current model, modulate the diffusion of rust according to tendencies based on the object geometry and environmental factors. Changing the underlying distributions of tendency allows images of a variety of metallic rusts to be generated. Published online: 28 January 2003     

Surface scratches: measuring, modeling and rendering

  One of the most important criticisms that can be made concerning synthesized images is the brand new and too clean aspect of objects. Surface color modifications can be used to introduce dirtiness or other aging-linked characteristics. Also, techniques such as bump or displacement mapping allow users to improve surface aspects by introducing geometrical perturbations. In parallel, the bidirectional reflectance distribution function (BRDF) is a crucial factor in achieving a high degree of realism. It turns out that surfaces are very often covered by defects such as scratches that are related to both textures and BRDFs due to their size. Scratches do not always affect the apparent geometry but nevertheless can remain strongly visible. None of the previously mentioned methods is suited for rendering these defects efficiently. We propose a new method, based on extensions to existing BRDFs and classical 2D texture mapping techniques, to render efficiently individually visible scratches. We use physical measurements on "real objects" to derive an accurate geometric model of scratches at small scale range (roughness scale), and we introduce a new geometric level between bump mapping and BRDFs. Beyond providing graphical results closely matching real cases, our method opens the way to a new class of considerations in computer graphics based on defects that require the coupling of both BRDFs and texturing techniques.     

Query by video clip

Typical digital video search is based on queries involving a single shot. We generalize this problem by allowing queries that involve a video clip (say, a 10-s video segment). We propose two schemes: (i) retrieval based on key frames follows the traditional approach of identifying shots, computing key frames from a video, and then extracting image features around the key frames. For each key frame in the query, a similarity value (using color, texture, and motion) is obtained with respect to the key frames in the database video. Consecutive key frames in the database video that are highly similar to the query key frames are then used to generate the set of retrieved video clips. (ii) In retrieval using sub-sampled frames, we uniformly sub-sample the query clip as well as the database video. Retrieval is based on matching color and texture features of the sub-sampled frames. Initial experiments on two video databases (basketball video with approximately 16,000 frames and a CNN news video with approximately 20,000 frames) show promising results. Additional experiments using segments from one basketball video as query and a different basketball video as the database show the effectiveness of feature representation and matching schemes.     

NeTra: A toolbox for navigating large image databases

We present here an implementation of NeTra, a prototype image retrieval system that uses color, texture, shape and spatial location information in segmented image regions to search and retrieve similar regions from the database. A distinguishing aspect of this system is its incorporation of a robust automated image segmentation algorithm that allows object- or region-based search. Image segmentation significantly improves the quality of image retrieval when images contain multiple complex objects. Images are segmented into homogeneous regions at the time of ingest into the database, and image attributes that represent each of these regions are computed. In addition to image segmentation, other important components of the system include an efficient color representation, and indexing of color, texture, and shape features for fast search and retrieval. This representation allows the user to compose interesting queries such as “retrieve all images that contain regions that have the color of object A, texture of object B, shape of object C, and lie in the upper of the image”, where the individual objects could be regions belonging to different images. A Java-based web implementation of NeTra is available at http://vivaldi.ece.ucsb.edu/Netra.     

Acquiring, stitching and blending diffuse appearance attributes on 3D models

Published online: 23 April 2002     

Multiresolution volume visualization with a texture-based octree

Although 3D texture-based volume rendering guarantees image quality almost interactively, it is difficult to maintain an interactive rate when the technique has to be exploited on large datasets. In this paper, we propose a new texture memory representation and a management policy that substitute the classical one-texel per voxel approach for a hierarchical approach. The hierarchical approach benefits nearly homogeneous regions and regions of lower interest. The proposed algorithm is based on a simple traversal of the octree representation of the volume data. Driven by a user-defined image quality, defined as a combination of data homogeneity and importance, a set of octree nodes (the cut) is selected to be rendered. The degree of accuracy applied for the representation of each one of the nodes of the cut in the texture memory is set independently according to the user-defined parameters. The variable resolution texture model obtained reduces the texture memory size and thus texture swapping, improving rendering speed.     

A JPEG-like texture compression with adaptive quantization for 3D graphics application

Published online: 2 October 2001     

Integrating E-Commerce and Games

This paper investigates how many users of commercial interactive systems are not properly agents within the interactive narrative, largely due to the dynamics of branding in cyberspace. Parallels are drawn between the dynamic personalization of e-CRM engines and context aware computing systems. Several seminal games are discussed as examples of systems in which very different relationships exist between users and the system. Arguments are made for designing e-commerce interactive systems that install into games, inside the game narrative. Correspondence to: Ms N. Cummins, Preject Brand Communications Consultancy, Unit P, Carlton Works Studios, Asylum Road, London SE15 2SB, UK. Email: nizami@preject.com     

Rain-Dancing with Pseudo-Science

In this polemical essay the authors ask whether computerisation has become the neurosis of our age. By comparing the application of IT methodologies with ritual behaviour within human social institutions, they propose that the so-called rationality of management science, with its tidy benchmarking, auditing, categorisation and performance measurements etc., is actually a pseudo-science. They show that from the position of Nietzschean epistemology, this rationality is merely a false claim to the instrumental efficacy of data modelling, that is indistinguishable from the rain-dancing of primitive tribes.     

Knowledge Networking in Cross-Cultural Settings

Knowledge networking in the cross-cultural setting here focuses on promoting a culture of shared communication, values and knowledge, seeking cooperation through valorisation of diversity. The process is seen here in terms of creating new alliances of creators, users, mediators and facilitators of knowledge. At the global level, knowledge networking is seen as a symbiotic relationship between local and global knowledge resources. This focus is informed by the human-centred vision of the information society, which seeks a symbiotic relationship between technology and society. It explores the nature of the knowledge in transition, raising issues of technology and knowledge transfer in the local–global context. The notions of human–machine symbiosis and of diversity and coherence provide a handle to explore the role of technology for sustainable development. The centrality of knowledge in stimulating knowledge networking for cross-cultural collaboration is illustrated through an exemplar of an EU–India Cross-Cultural Innovation Network project, a collaboration between European and Indian universities and institutes.     

Taxonomy of interpolation constraints on recursive subdivision surfaces

Published online: 14 May 2002     

Designing wrapper components for e-services in integrating heterogeneous systems

Component-based approaches are becoming more and more popular to support Internet-based application development. Different component modeling approaches, however, can be adopted, obtaining different abstraction levels (either conceptual or operational). In this paper we present a component-based architecture for the design of e-applications, and discuss the concept of wrapper components as building blocks for the development of e-services, where these services are based on legacy systems. We discuss their characteristics and their applicability in Internet-based application development. Received: 30 October 2000 / Accepted: 9 January 2001 Published online: 28 June 2001     

Causality and atomicity in distributed computations

Summary. In a distributed system, high-level actions can be modeled by nonatomic events. This paper proposes causality relations between distributed nonatomic events and provides efficient testing conditions for the relations. The relations provide a fine-grained granularity to specify causality relations between distributed nonatomic events. The set of relations between nonatomic events is complete in first-order predicate logic, using only the causality relation between atomic events. For a pair of distributed nonatomic events X and Y, the evaluation of any of the causality relations requires integer comparisons, where and , respectively, are the number of nodes on which the two nonatomic events X and Y occur. In this paper, we show that this polynomial complexity of evaluation can by simplified to a linear complexity using properties of partial orders. Specifically, we show that most relations can be evaluated in integer comparisons, some in integer comparisons, and the others in integer comparisons. During the derivation of the efficient testing conditions, we also define special system execution prefixes associated with distributed nonatomic events and examine their knowledge-theoretic significance. Received: July 1997 / Accepted: May 1998