Talks and Poster Presentations (with Proceedings-Entry):

W. Karel:
"Sophisticated Use of Virtual Shapes of Architecture and Visualization of Quality";
Poster: International Symposium of CIPA, Turin, Italien; 2005-09-26 - 2005-10-01; in: "International Cooperation to Save the World's Cultural Heritage", S. Dequal (ed.); International Archives of Photogrammetry Remote Sensing and Spatial Information Sciences, Vol. XXXVI-5/C34 (2005), ISSN: 1682-1750; 882 - 887.

English abstract:
The object of this project was the creation of a precise photorealistic model of the Romanesque church of San Juan del Hospital in Valencia, Spain. The church building should be modelled with a geometric accuracy, a level of detail, and a texture resolution of 5cm, the neighbouring pavilion even with 2cm, respectively. To reach this with economically reasonable efforts despite the complex geometry and difficult accessibility, virtual shapes of architecture (also called `fictitious observations´ or `Gestalts´) were integrated into the modelling process. The application of virtual shapes takes advantage of the fact that even ancient buildings were created on the basis of a plan, delimiting the object mainly with planes and straight edges. This means that in the simplest case, it can be presumed that points on the same face of a wall reside on a (vertical) plane. More sophisticated surfaces and curves can be applied to arcs and cupolas. The same virtual shapes were used for all objects built the same way (e.g. columns). Furthermore, symmetries were considered. Many areas on the building could only be pictured in one photograph. Thus, photogrammetric or polar spatial intersection was impossible there. Nevertheless, vertices within these areas could be determined by usage of shape assumptions. Additionally, the application of virtual shapes enhanced the determination of points on lines in poorly textured areas. The extensive use of virtual shapes is not the only innovation in this project, but also the visualization of the photorealistic model. Users may not only inspect the model itself, but also the modelling quality as a meta-information. Having activated a model vertex, the quality of point determination is visualized numerically by the three coordinate standard deviations and by the number of observations that were employed to determine the point. Moreover, quality is viewed graphically by the point's photogrammetric and tachymetric observation rays in space and by fading in the point's error ellipsoid.

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