The Division of Virtual Reality Techniques was founded in March 2013 by a group of employees whose research interests reached beyond the areas investigated in their home unit, the Division of Photonics Engineering (under prof. Małgorzata Kujawińska). They are led by a WUT professor, Robert Sitnik, Ph.D., D.Sc. Projects completed by the team include Anna and Jarosław Iwaszkiewicz Virtual Museum in Stawisko with 3D digitisation and interactive presentation of part of the collection of the Museum. The Division is now working on 3D digitisation in the Museum of King Jan III’s Palace in Wilanów; they are scanning the interiors of a unique room – the King’s Chinese Study. We shall take a closer look at the method that changes real-life objects into digital ones.

What is 3D digitisation?

Robert Sitnik: 3D documentation means digital representation of the geometry of the measured object with a given precision and resolution. This basic representation may be complemented with additional values specified for a given measurement point, such as colour or normal vectors. Data that fail to meet the requirement of the given precision of representation may be used for visualisation and presentation purposes but they should not be treated as documentation.

3D digitisation, 3D documentation is transformation of a real-life object into its 3D digital image (the most common use is 3D scanning, which allows to obtain coordinates [x, y, z] of the surface of a real-life object in the Cartesian coordinate system)*.

3D digitisation is usually used in documentation (also conservation documentation) for visualisation, e.g. for a poster or for promotional purposes. Documentation activities are aimed at making such a copy of an object that there should be no need to remake it in a few years’ time. If there is such need, this may be done only for the purposes of monitoring the occurring changes and determining the current condition of the object.

Conservation documentation is made before the restoration process or directly after it (or both before and after) in order to check the influence of the process on the object. The most precise is the so-called permanent documentation, which by definition should be the most precise representation. If in future the object is damaged or something happens to it, we will have reliable data on its previous condition.

What is the documentation made on?

RS: We make it on digital media (disc arrays) and on tapes. Thanks to the server infrastructure of the National Institute for Museums and Public Collections, all the data are collected and secured centrally. Moreover, data are kept in the same way as banks keep the data of their clients. Objects for every-day access are stored on disc arrays and long-term copies are saved on magnetic tapes.

Automation of the process will be connected with…

RS: …as little human participation as possible. If we assume that we wish to scan the whole historic room, first a team of restorers should gather to determine the precision of the work. In the King’s Chinese Study, we made our measurements with the resolution of 0.1 mm, where the distance between the measurement points was 0.1 mm and measurement uncertainty was 50 micrometers. We had to make over 12,000 such measurements.

Manual realisation of the measurements by the human is difficult because operators change and they have to forward information to others quickly. Additionally, during measurements often they are unable to load the whole model or they forget to scan some part of the object. We aim at eliminating all activities that require mundane and repeatable actions on the part of the operator. In the end, the operator should mainly decide on the strategy of the actions. Whether all surfaces have already been scanned or not, is constantly checked by an algorithm. In the Wilanów Museum we scanned circa 100 m² of the surface of the walls and ceiling with a robotic arm. The robot could not be placed to reach the whole room so it scanned metre-per-metre fragments in one coordinate system. The whole work took around one month.

During measurements with the robotic arm, the initial path is determined automatically. The operator only follows it and, for example, points to places that should be measured additionally. Then, the measurement head on the robotic arm is moved to an appropriate place. After the measurements, all fragments are put together to make the whole image.

What makes the King’s Chinese Study so special?

Eryk Bunsch (Museum of King Jan III’s Palace in Wilanów): This room is richly decorated in the so-called European lacquer technique. There are very few such rooms in Europe, therefore they are invaluable. This is the only interior in Poland decorated in this way. Recently the study underwent very complicated conservatory work. It lasted over two years and its main aim was to restore the original colours, which changed under the influence of light. 3D documentation of the interior was made two times – before the beginning of the work (in 2009) and after it ended (in 2015). The decision to create such technologically advanced documentation of the interior was taken for two reasons. Firstly, we needed to register the condition of the room before the beginning of the work to have an opportunity to compare the data with the documentation made in that year. Secondly, for conservation reasons (small size of the interior and extraordinary sensitivity of the surface) it is impossible to allow visitors in the room. The registered virtual model will give an opportunity to show all details of this extraordinary exterior to a great number of tourists through digital media.

The present decoration of the Chinese Study was created in 1731-1732 upon the order of King Augustus II the Strong by Martin Schnell, who made artistic handicraft decorated with European lacquer. The walls of this small corner extension are decorated with panels with lacquer imitating the technology and decorating elements of Chinese lacquer**.

How large can objects for digitisation be?

RS: Our Division deals with structural lighting and we are developing it. The method is appropriate for scanning objects circa 2 metres high. In measurements, we use a projector that lights the whole surface. At present there are no sources efficient enough to light, for example, a building. For such objects, lasers and laser-based measurement are used. These are architectural and geodetic systems that use the methods of the time of light or phase shift and scan in the spherical system in the area of even a few hundred metres. The beam is rotated in all directions and the distance from the scanning place is measured with the precision of circa 4 mm. For a large building, this is sufficient. For interiors and small objects, where high precision is required, we use our systems.

What is the essence of a virtual museum?

RS: To prepare a presentation at a high level, one needs to plan it in detail, find the means and then realise it well. A virtual museum is a museum in which one can interact in real time and have simultaneous 3D visualisation. Whether looking around is also virtual observation or not, is a matter of definition.

In the virtual world, many scenarios must be realised, like in a computer game. There arises then the question whether 3D museums are virtual or if they only use 3D presentations. In terms of marketing, it sells very well but it is much more difficult to determine the reality unambiguously.

Wilanów has its own 3D digitisation office in the museum structure. At present, they are finishing its renovation and equipment is being installed. The office scans following the museum procedure, i.e. maintaining the whole process from the technological line to 3D scanning. At the next stage, we are planning to set up a company which will deal with a wider implementation of our solutions on the Polish and global museum market.

Recently, the 17^th Chopin Festival ended. And so my question about Frederic Chopin’s piano, which your team realised in 2010 in cooperation with the Adam Mickiewicz Institute.

RS: This multimedia visualisation of the antique piano made by Ignacy Pleyel, on which Frederic Chopin played and created in Paris in the last years of his life, was prepared in connection with the 200^th anniversary of the composer’s birth in 2010. We developed an interactive model with precise representation of the geometry, texture, movement of individual elements and real sounds registered on the Pleyel piano of the National Frederic Chopin Institute. The piano can be seen from outside and inside and one can touch its keys. The presentation allowed to compose, save and play one’s own pieces of music. Playing the instrument was done by clicking a mouse or with a computer keyboard. The WUT coordinator of the project was Marcin Witkowski, Ph.D.

Plans for the future?

RS: In cooperation with three companies and with the financial support of the National Centre for Research and Development, we are taking up the challenge of the 4D|BODY project, which measures the man in movement, at the speed of 120 times per second. We will try to find better applications than those used currently. They could cover fields such as medicine, rehabilitation, graphics or special effects. The project will involve circa 15-16 specialists from various areas.

* Criteria of the choice of a 3D technique for documentation of cultural heritage objects. Digitisation in museums 02/2014. Eryk Bunsch. Robert Sitnik. National Institute for Museums and Public Collections. Warsaw 2014.
** Part of an article ”Conservatory work in the King’s Chinese Study” www.wilanow-palac.pl

Photos by Eryk Bunsch, Museum of King Jan III’s Palace in Wilanów; WUT Bulletin

The article comes from the WUT Bulletin. Interview by Izabela Koptoń-Ryniec