surface mesh

IMAGE BASED MODELING OF GRAVE COVERINGS AND EPITAPHS

This Web page is a supplement to the CIPA 2015 contribution: Pomaska, G. and Dementiev, N. Towards Image Documenation of Grave Coverings and Epitaphs for Exhibition Purposes

Epitaphs and memorials as immovable items in sacred spaces provide with their inscriptions valuable documents of history. Today not only photography or photos are suitable as presentation material for cultural assets in museums. Computer vision and photogrammetry provide methods for recording, 3D modeling, rendering under artificial light conditions as well as further options for analysis and investigation of artistry.

The items to be recorded consists of cast iron and black polished marble. Under the existing light conditions it is a challenge to photography and illumination. Due to the illustration of the fine textures in the marble it is obvious that we need an image texture from high resolution photographs. Applying the structure from motion method provides a very flexible exposure arrangement particular under the unfavorable light environment. Manipulation of texture maps and artificial light settings for the renderings may compensate the difficult conditions on site. The major topics of this contribution may be listed as:

  • Structure from Motion / Photogrammetry
  • Mesh processing and 3D printing
  • Renderengine Blender
  • Raspberry Pi image presentation software
  • GPIO interface

The full paper will be published after the conference.

 

Grave Coverings Stadtkirche Herborn
 

Johannes Alent

Johannes Piscator 1584-1625

Johannes Melchior 1646-1689

Grave Covering Königslutter Dom
 

Animated light direction

Photo textured model

Surface maesh - detail
Click here for 3D

Unknown grave figure Stiftskirche Altenberg
 

View with red-cyan anaglyph glasses

Photo textured model

Solid model

 

 

Structure from Motion

In computer vision structure from motion (SFM) indicates the process detecting spatial structures of objects due to corresponding features from images. SFM targets to the use of non calibrated cameras and totally automatically model reconstruction. The final object geometry is given as a sparse or dense colored point cloud including the camera positions and intrinsic parameter. The working chain denotes with three corner stones: feature extraction, matching and adjustment.

Amongst the several distributions of SFM software Autodesk provides with 123DCatch a freeware solution. A mesh is generated via online service and can be finished offline. The illustration displays the camera positions and fades in one photo into the 3d mesh. Applying a remote controlled camera (here Olympus OMD with Android Smartphone) is a big advantage in picture taking on site.

3D Modeling & Printing

Producing a replica of a figurative epitaph or a capital figure as shown in the instance here needs a watertight mesh. The photogrammetric surface comes as an uncompleted relief. This relief must be refined to a solid. The process requires cleaning and reducing the point cloud with consistent orientation of the normal vectors and elimination of non manifold edges. Furthermore registration of the meshes and orientation with scaling have to be carried out before the solid can be sent to the printer output. Another major topic is the hollowing, bearing in mind the material and dimensions of the replica. as the illustration here shows. The item is cutted in the middel for demonstartion purposes. In addition two holes may be added to enable removing the unused printing material from inside the figurine.

Quite a few software tools are available to finalize the production. Some of the most common applications are Meshlab for modeling and Blender for modeling, rendering and animation as open source. Meshmixer from Autodesk as freeware supports model preparation and printing as well as NetFabb with its different licence models.

 

 

Solid model hollowed for 3D printing

View 3D model with anglyph glasses

Presentation

Raspberry Pi and a Python driven software will be the platform for presentation at exhibitions. There is a non-interactive system under construction, that will be driven by rugged pushed buttons. Initialization of the system requires only power on switching. The Linux environment will automtically start the software, switches screensaver off, puts the monitor in portrai mode and installs server for maintening the system by PC or Smarthphone operating if necessary. The Phyton script and more detailed information about coding can be found under www.divide-by-zero.com. Some You Tube video clips are linked as follows:


Responsible for the content of this page is Prof. Dr.-Ing. Guenter Pomaska, http://www.imagefact.de
Please don't use any of the images without permission of the author.