EG UK Theory and Practice of Computer Graphics 2013

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https://diglib.eg.org/handle/10.2312/908

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Browsing EG UK Theory and Practice of Computer Graphics 2013 by Subject "I.3.3 [Computer Graphics]"

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    Acquisition, Representation and Rendering of Real-World Models using Polynomial Texture Maps in 3D
    (The Eurographics Association, 2013) Vassallo, Elaine; Spina, Sandro; Debattista, Kurt; Silvester Czanner and Wen Tang
    The ability to represent real-world objects digitally in a realistic manner is an indispensable tool for many applications. This paper proposes a method for acquiring, processing, representing, and rendering these digital representations. Acquisition can be divided into two processes: acquiring the 3D geometry of the object, and obtaining the texture and reflectance behaviour of the object. Our work explores the possibility of using Microsoft's Kinect sensor to acquire the 3D geometry, by registration of data captured from different viewpoints. The Kinect sensor itself is used to acquire texture and reflectance information which is represented using multiple Polynomial Texture Maps. We present processing pipelines for both geometry and texture, and finally our work examines how the acquired and processed geometry, texture, and reflectance behaviour information can be mapped together in 3D, allowing the user to view the object from different viewpoints while being able to interactively change light direction. Varying light direction uncovers details of the object which would not have been possible to observe using a single, fixed, light direction. This is useful in many scenarios, amongst which is the examination of cultural heritage artifacts with surface variations.
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    Multi-Perspective Detail+Overview Visualization for 3D Building Exploration
    (The Eurographics Association, 2013) Pasewaldt, Sebastian; Trapp, Matthias; Döllner, Jürgen; Silvester Czanner and Wen Tang
    Virtual 3D building models, as key elements of virtual 3D city models, are used in a growing number of application domains, such as geoanalysis, disaster management and architectural planning. Visualization systems for such building models often rely on perspective or orthogonal projections using a single viewpoint. Therefore, the exploration of a complete model requires a user to change the viewpoint multiple times and to memorize the content of each view to obtain a comprehensive mental model. Since this is usually a time-consuming task, which implies context switching, current visualization systems use multiple viewports to simultaneously depict an object from different perspectives. Our approach extends the idea of multiple viewports by combining two linked views for the interactive exploration of virtual 3D buildings model and their façades. In contrast to traditional approaches, we automatically generate a multi-perspective view that simultaneously depicts all façades of the building in one overview image. This facilitates the process of obtaining overviews and supports fast and direct navigation to various points-of-interest. We describe the concept and implementations of our Multiple-Center-of-Projection camera model for real-time multi-perspective image synthesis. Further, we provide insights into different interaction techniques for linked multi-perspective views and outline approaches of future work.
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    Resolution Estimation for Shadow Mapping
    (The Eurographics Association, 2013) Ferko, Michal; Silvester Czanner and Wen Tang
    We present an approach to efficiently reduce shadow map resolution while retaining high quality hard shadows. In the first step, we generate a list of sample points that are seen from the camera and then project these into light space, much like Alias-free Shadow Maps. In the next step, we analyze the list of sample points on the GPU to construct a tight light frustum for shadow rendering. After the light frustum is computed, we calculate for each sample the actual coverage in the final shadow map to estimate how large a shadow map pixel should be. From this number, we derive the lowest possible resolution to use in the shadow map while retaining nearly alias-free shadows. Our algorithm is built for a deferred renderer.
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    StegoNPR: Information Hiding in Painterly Renderings
    (The Eurographics Association, 2013) Lord, Craig; Collomosse, John; Silvester Czanner and Wen Tang
    We present a novel steganographic technique for concealing information within an image. Uniquely we explore the practicality of hiding, and recovering, data within the pattern of brush strokes generated by a non-photorealistic rendering (NPR) algorithm. We incorporate a linear binary coding (LBC) error correction scheme over a raw data channel established through the local statistics of NPR stroke orientations. This enables us to deliver a robust channel for conveying short (e.g. 30 character) strings covertly within a painterly rendering. We evaluate over a variety of painterly renderings, parameter settings and message lengths.