Heidelberg University

Visualization and
Numerical Geometry Group


ILATO - Improving Limited Angle computed Tomography by Optical data integration

Alu sample

From a finite number of X-rays detected after travelling through an object, sinograms representing attenuation values of specimen are acquired. The 3D information is reconstructed from a series of 2D projections mostly on a circular trajectory. Limited angle computed tomography is indicated whenever the specimen dimensions exceed cone beam limits or the object is impenetrable from certain angles. Thus, acquiring only a subset of a full circle CT scan poses problems for reconstruction algorithms due to incomplete data which introduces blurred edges and other artifacts. A surface mesh acquisition of the object obtained via structured light optical scan is not limited in angle but cannot reveal the volumetric structure inside. The project focuses on the registration of optically acquired surfaces with data acquired from computed tomography in order to enhance image quality and shorten acquisition times in X-ray based industrial quality inspection (project page).

Angkor discovery

Mold of the Facetower in Angkor Our activities at various places in Cambodia were accompanied by an ARTE camera team (German/French TV channel) in spring 2013. In close collaboration with the French archaeologist Eric Bourdonneau (EFEO) and our project coordinator Pheakdey Nguonphan (IWR/RUPP) we selected those fragments of an approximately 6 m high Śiva-Statue from Koh Ker and scanned it in 3D. The various parts of the puzzle are located in the temple on site as well as in the museums in Phnom Penh, Siem Reap (Cambodia) and in Paris (France). Due to the thoroughgoing investigations of the King's temple of Koh Ker, Eric Bourdonneau could furnish proof that these great temples had the purpose of intramural burials: They served King and subjects as gate to the afterworld. We contributed the high resolution 3D scans (structured light) and photogrammetric reconstructions of the real objects. Thereafter the inner of the various chappels of the temples, whose statues had been stolen by tomb raiders long time ago, were animated in Paris on behalf of Iliade Productions (Frédéric Wilner). Here comes the link to the ARTE documentary (86 min) on the temple in Cambodia with the premiere on Sat, Oct 5, 2013, 20h15 (repeated on Sun, Oct 6, 14h20) on the ARTE-TV channel and the link to the exhibition in Musée Guimet, Paris (October 16, 2013 - January 13, 2014)

The puzzle on the broken Śiva-Statue of Koh Ker has its own project page.

3D-Scans of medieval inscriptions on the Jewish Cemetery "Heiliger Sand", Worms

Stein No. 1061 A 3D close range scanner is used for the digitization of inscriptions of medieval gravestones on the Jewish Cemetery "Heiliger Sand" in Worms. The question is the acquisition of the today's status in an ongoing weathering of the sandstone surface. Subsequently the digitized surfaces are analysed according to additional characters to be deciphered, which have not already been decoded with sided light photography. First results can be found on the project page .

Scientific computing on data of mid range and close range laser scanning

cuneiform in false color Mid range and close range laser scanning for surveying sites become more and more popular. The results are extremely large data sets of (meshed) point clouds. We combine methods from scientific computing with demands of cultural heritage sites to draw the interesting information out of this data. Automated texturing with adaptive meshing is done as well as terrain-based level of detail mesh simplification. Reconstructions of a complex building, potsherds and broken fragments shall be automated based on multi-scale integral invariants used for 3D puzzles. Combing our knowledge on image filtering with 3D surface data shall result in automated transscriptions of scripts (epigraphy) for ancient documents (Assyrian cuneiform, Greek inscriptions, Chinese sutras).

GPGPU computing for applications in medical visualization techniques

engine block Programmable graphics cards or General Purpose Graphical Processing Units (GPGPU) accelerate the computing time tremendously. But not every algorithm can benefit from this architecture. Our main focus is the evaluation of algorithms due to their applicability on topics such as particle filtering methods or anisotropic nonlinear diffusion filtering used in medical applications. We already have experiences with volume rendering techniques successfully implemented with Compute Unified Device Architecture (CUDA) and are currently investigating the use of parallelization in fluid visualization techniques.

Geometry Reconstruction

grid of a human lung The software NeuRA2 is a toolbox of many sophisticated image processing and mesh generating operators. It enables the reconstruction of triangular surface meshes, tetrahedral volume meshes and feature skeletons from image stacks or single images. NeuRA2 is developed at G-CSC Frankfurt and IWR Heidelberg. It was successfully used in various application projects.

SiGHTSee - Simultaneous Generation in Heidelberg: Text and Scene images

NW_BirdView of INF In this FRONTIER-project in cooperation with linguistics we want to model the mutual specification of the two modalities language and vision, paired with the striking contrasts we find in how one and the same visual image is verbalised in different languages. Language and vision mutually disambiguate each other thus allowing for more efficient conveying of communicative goals. Different languages tend to verbalise visual scenes in different ways. Reconciling these two aspects within a coherent architecture is difficult. At the same time, it is crucial for the design of naturally sounding multilingual systems.

Baroque Globes, Restoration and Reconstruction

Gottorfer Globus Anisotropic Diffusion Filtering is suited best for hatching and scripture in digital images. This method was successfully applied to the gores of the University's own Vaugondy Globe of 1751. Following that, we took part in the reconstruction of the Giant Gottorf Globe, where we supplied a digital master for the outside painting by filtering and upscaling a 17th century Blaeu globe.

Lorsch Abbey Reconstruction and Information System

Kloster's garden This interdisciplinary project aims at a verifiable reconstruction of Lorsch Abbey (UNESCO World Heritage) throughout its history. Hypotheses of different scholars will be visualized and can be evaluated by the user of the system. This flexible approach shall enable scientists and lay people to form their own opinions about the site. For more information visit the project home page.

Virtual Cloud Impressions

Cloudless sky over Germany Daily virtual 3D cloud animations from different perspectives on Europe and South Asia are transcribed as animates GIFs with volume visualization techniques. The gray values of the satllite images are used for height information. For the animations visit the home page of the project.

Sierpinski Tetrahedron

Sierpinski Tetrahedron step 1 The Sierpinski tetrahedron is a fractal structure, which was rendered in this illustration with metal spheres at each of its vertices and with a raytracing method. The fractal dimension can be made plausible by casting a shadow from a certain position. See also the home page of the project.

Angkor Project Group

IWR Group in Angkor Angkor Wat in Cambodia is the greatest temple area of the world. First we were engaged in the architectural reconstruction with computer methods. Since the beginning of 2005 there is a student project "Angkor Project Group" with its own home page. A first excursion to Cambodia took place in April 2005. Contacts to the German Development Service (DED) and the World Monument Fund were made. A return visit of students from Cambodia with the help of UNESCO scholarships took place in October/November 2005 and again in October 2006.


Detail eines Ilkhanidischen Muqarnas Since the early nineties we have been involved with Islamic architecture and mathematics. From that time results a scientific film "Qubba for al-Kashi" about the various arcs and vaults and their construction. Furthermore it contains a reconstruction of the observatory in Samarqand. Since October 2002, the German Ministry for Education and Research (BMBF) funds a project for the mathematical and computer scientific treatment of Muqarnas plans (see the home page).

S. Krömker, 
Last Update: 12.07.2016
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