Theseustemple in Vienna

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The Theseus-Temple in Vienna

Creating a 3D model from "Amateur" photographs

Introduction

In spring 1998 I held a lecture dealing with photogrammetrical applications in archaeology at the Institute for Prehistory and Early History in Vienna. The aim of the lecture was to give students of archaeology a basic knowledge of photogrammetrical techniques and to put this knowledge into practice. Therefore, we decided to make a 3D-model of the Theseus-Temple in Vienna using "low-cost" equipment and software.

The Theseus-Temple

The Theseus Temple is located in the "Volksgarten", a public garden in the first district of Vienna next to the "Burgtheater". It was built in the 1930ies.

Documentation

The temple was recorded using simple amateur Cameras and the "3x3 rules". The temple was photographed from different positions, so that every point, that would contribute to the 3D-model later on (corner, column, steps, roof...), was recorded on at least 3 photographs. Additionally, to be able to scale the model later on, 8 targets were attached to the temple walls and the distances between them were measured. During the documentation, a scetch was drawn including every photo position, the measurements and other important information.

	One of the photographs, which was taken during the recording procedure. On the left side, two fiducial marks (having the shape of three triangles) can be seen. These were glued into the camera frame to make our amateur camera a semi-metric one.
	One of the eight targets, which were sticked to the temple´s walls. The distances between them were measured. In that way, the model could be provided with a scale.
	Scetch drawn by some of the students. It shows the temple and the position of the targets with measured distances. Additionally, the photo-positions (i.e. from where the photographs were taken) with distances to the temple were recorded.

Modelling the Temple

For the modelling procedure, "PhotoModeler®", developed and distributed by EOS Systems, Vancouver, Canada, was used. It is a low-cost-software for extracting measurements and 3D-models from photographs, which runs on a PC.
The students were divided into several groups. Each group made its own 3D-model.
7 basic steps were needed to create the 3D-model out of the photographs.

Photo-Import, i.e. the photographs had to be scanned with at least 1000 DPI
Marking of object points: every object point, that would build the 3D model had to be marked in every photograph. In our case over 700 individual object points were marked in up to 5 photographs each.
Identify and reference the identical marked object points.
Calculation of the camera positions and orientations. During the same procedure, also the 3D coordinates of every marked and referenced object point are calculated. The result is the basic 3D-model with estimates of errors for every point.
Scaling the model: this is done by telling the program the real distance between two object points, which was measured during the recording procedure (in our case the distances between the targets).
Refining the 3D-model: additional points can be marked and referenced, lines can be drawn between each 2 points etc...
Export of the data to other CAD packages to render the model, produce animations etc.

The accuracy depends on several factors as e.g. the quality of the used camera, the angle between the viewing directions of the photographs, the number of photographs on which each point is marked, the scanning resolution etc. In our case, the accuracy averaged between 5 and 15 cm.

	Screenshot with all photographs opened. The points are already marked in all photographs.
	Detailled screenshot with one photograph. The points are marked and referenced. The small tags next to the points show the IDs.
	3D-viewer with the resulting 3Dpoints and lines after calculation of the camera positions and orientations.
	3D-viewer with the resulting 3Dpoints, lines and calculated camera positions.
	Screenshot of the 3D-viewer with the partly finished surface model of the temple.

Result and Further Work

After the model of the temple was at a satisfying level of detail, the data were exported and used in other applications, as CAD-systems, programs for digital image enhancement and 3D-rendering and animation software.
The few following examples will show you a few possibilities, what you can do with the finished 3D-model.

	VRML-File (Virtual Reality Modeling Language) of the temple.
	Rendered view of the model. The 3D-data of the temple and the camera positions were imported into a 3D-rendering software. During the rendering procedure, the photographs were projected on the model using the "digital projector technique".
	Another rendered view of the temple. Since it is an orthographic projection, the picture is like an orthophotograph.
	Orthophoto of the architrav, produced by PhotoModeler®.
	Anaglyph of the model created by rendering two different views and coloring and combining the two images. You can watch this picture in 3D, if you have red-green-spectacles or simply hold a red film over the left eye and a green film over the right eye.

Rendered animation of the 3D-model. Since the file has around 200K, loading can take a while!

Rendered 3D-animation of the temple. Again, you need a green and a red film in front of your eyes.

References

Lecturer:	Michael Doneus
Assisting lecturer:	Andreas Rausch
Participants:	Ingrid Adenstedt, Edeltraud Aspöck, Ing. Konrad Inzinger, Martin Janner, Mathias Mehofer, Ines Ruttner, Nicole Pieper and Daniela Straznicky

Literature:

HANKE K., EBRAHIM A.-B. M.: A General Approach for Object Oriented 3D- Mapping in Digital Close Range Restitution. Proceedings des ISPRS - Congress, Vienna 1996. International Archives of Photogrammetry and Remote Sensing Vol. 31 / 5.
HANKE K, EBRAHIM M.A-B.: Monument Presentation using Digital Architectural Photogrammetry. Paper presented at the CIPA Symposium 1997, Göteborg, Schweden. International Archives of Photogrammetry and Remote Sensing Vol. XXXI Part 5C1B.
HANKE K, EBRAHIM M.A-B.: A low cost 3D-Measurement Tool for Architectural and Archaeological Applications. Paper presented at the CIPA Symposium 1997, Göteborg, Schweden. International Archives of Photogrammetry and Remote Sensing Vol. XXXI Part 5C1B.
PhotoModeler® Pro, User Manual. 12th Edition, Eos Systems Inc., Vancouver 1997.
WALDHÄUSL, P., OGLEBY, C.: 3-by-3-Rules for Simple Photogrammetric Documentation of Architecture. In: J.G.Fryer (Editor): Close Range Techniques and Machine Vision. Proceedings of the Symposium of Commission V of ISPRS in Melbourne, Australia, 1-4 March 1994. IAPRS XXX/5, 1994, 426.

Links:

Homepage von PhotoModeler®
CIPA (Comite International de la Photogrammétrie Architecturale)