ATOR (Arc-Team Open Research).
The blog spreads tests, problems and results of Arc-Team research in archaeology, following the guidelines of the OpArc (Open Archaeology) project.
This post is a further contribution regarding the main benefit of SfM: its versatility.
Thanks to its speed during the phase of data acquisition, this technique allows us to intervene quickly in the case where the archaeological excavation exposes precarious situations, often related with collapsing structures.
The image below is good example: we were working in the vicinity of a church, checking the excavator. The left pictures shows the part of a wall which was exposed during this operation, while the right photo reports the same subject just twenty minutes later.
The wall befor and after the collapse
Luckily, seen the precaurious conditions of the structure, we decided to document it with SfM and IBM techniques, and this is the 3D restitution of the wall before the collapse.
The 3D model of the wall
However, the documentation of archaeological arthefacts before their destruction, is just one of the benefits of SfM (mainly related with the speed during data acquisition). In fact the versatility of this technique is strongly connected with the hardware we need to collect the data: a simple digital camera. This make it possible to work without the necessity of a direct contact with object to be documented (especially if we can support the excavation with a direct reflex total station, to record the Ground Control Points needed in the post-processing georeferencing operations). This way to operate lead to minimize the risk and increase the safety in the workplace. The images below regard an example of this situation: sometimes it happen to be called to evaluate the damnages of costruction sites, already underway without the archaeological control. In these cases it can happen to document precarious situation, but, using SfM techniques, there is no need to stand in risky places (like under a section with many gravel layers), because all the operations can be done from a safety distance.
To complete the "Kinect trilogy", today I write this post about our first test during a real archaeological fieldwork.
Also in this case we (Alessandro Bezzi and me) used our "hacked Kinect" with the external battery in connection with the rugged PC and, again, the chosen software for data acquisition was RGBDemo. This time we documented in 3D a layer during an "indoor" excavation, to avoid the problems with direct sunlight I descirbed in this post.
The video below tries to summarize this operation...
... and here are some screenshots to have an idea of the final result:
The pointcloud (frontal view)
The pointcloud (side view)
The mesh
The mesh (wireframe)
As you can see the general quality is lower respect the results we can obtain with other techniques (e.g. SfM and IBM), but Kinect and RGBDemo have the benefit to acquire and elaborate the data almost at the same moment, with the possibility to see the documentation process in real time.
Ultimately Kinect is one more option to consider for 3D indoor documentation, considering the peculiarities of the archaeological project (the light conditions, the available time, the required level of detail, etc...). Our experiments will now go on now with some tests in particoular situations, where this technique could be the best option (expecially in underground environments).
It was a sunny September Sunday, so I decided to take a walk with my wife Kathi and show her one of the hermitages located in the valley in which we live (Val di Non, Trentino, Italy).
My second thought was that the ramble was a perfect opportunity to test the hacked Kinect and try to document in 3D the main wall of S. Gallo's ruins (the remains of the hermitage). So I prepared the backpack with Kinect, the external battery and the rugged pc we normally use on the archaeological excavations.
After half an hour's walk throught apple orchards and woods we reached the hermitage. Along the way we also found a stunned rooster. That was strange! A rooster, in italian "gallo", in the S. Gallo's hermitage...
However, we began to try to document the main wall of the ruins, which you can see in the picture below...
S. Gallo's hermitage, with the rooster
... but, probably due to direct sunlight conditions, Kinect and RGBDemo where not working propertly.
In fact, as you can also read in M. Dalla Mura, M. Aravecchia and M. Zanin poster (during "LOW COST 3D: sensori, algoritmi e applicazioni" workshop), "...The main issue is due to direct Sun illumination that leads to saturation in the depth acquisition...". Moreover the software (RGBDemo) was reacting very slowly, but this was probably due to the hardware (Panasonic Thougbook), which is less powerful compared to the laptop I normally use to work. Secondly also RGBDemo seems to work better on GNU/Linux (ArcheOS), the Operating System which runs my laptop, than in Windows, the rugged PC OS (but this could be just my impression).
Not beeing satisfied with the results I get with the 3D documentation of the ruins (software too slow to manage all the data recording process, high errors on the sunny parts of the wall, etc...), I decided to check for another subject to document. Luckily in S. Gallo's hermitage are not missing the caves, so, with the help of Kathi, I did a fast digital 3D copy of the cave you see in the picture below.
S. Gallo's cave
This time the software was working good, fast enought to work on the field and with negligible errors in data acquiring. In the movie below it is possible to see the final pointcloud (not complete, but big enought to understand the quality of a 3D "field" documentation with Kinect).
After this test, our Kinect was ready to the "trial by fire" of a real (indoor) archaeological excavation, which will be the topic of one of the next posts in ATOR.
Some weeks ago I finally found the time to modify our Kinect in order to test it outdoor.
My main problem was the power supply, while in an archaeological excavation it can be difficoult to find an access to electricity. The solution was obviously an external battery, but I did not know the right voltage and amperage. Finally I found this interesting post, in Ken Mankof blog, with all the necessary informations to hack Kinect for the fieldwork.
I tried to summarize all the operations I did in the image below:
The modified Kinect
As you can see, Kinect's main cable ends with an USB (for data transfer) and with an electric plug (for power supply). I cut the cable before the elctric plug and I added a connectors pair, positioning the male one on the Kinect side and the female one on the electric plug side. Then I prepared another cable with a female connector at one end and two different female blade connectors (faston) on the other end (one for the positive and one for the negative exit). The two female blade connectors are compatible with the two terminals (red/positive and black/negative) of a lead battery (12 V, 7.2 Ah). In this way it is possible to switch Kinect form the electric net to the battery, simply plugging and unplugging the right cables.
After the hardware modification I was able to test Kinect outdoor. I will write soon a post with the results.
Recently we talked about prototyping applied to the museum context. Maybe for those who are not accustomed to such matters, this argument can seem quite difficult to understand.
In particular, it may be difficult to imagine a 3D printer that works to build dioramas. The idea of diorama, in fact, remained quite frozen in the representations housed behind the windows of the natural history museums of the nineteenth century and much of the twentieth century.
These are hand-crafted dioramas, often made using materials taken from the natural environments of origin of the animals of which is meant to represent the habitat. Today, the dioramas are designed differently, meeting even the most modern artistic aspect in some successful demonstrations.
To aid people to understand, I'll give an example of prototyping completely divorced from the museal context. In fact, I will speak of the use of prototyping in fashion, illustrating the work of Iris van Herpen.
Iris van Herpen, born in Holland in 1984, became known for his clothes really special: two of her cherished customers are Lady Gaga and Björk.
After a sketch of the dress, Van Herpen drapes it on a virtual model and then entrusts the result to Materialise, a Belgian company that makes 3D prints. As she says, during this process, his tailoring is transformed into a laboratory where creation, emotion and technology fuse together to give a really particular aesthetic vision.
What impressed the fashion world, it was the perfect combination of craftsmanship knowledge and applications of new technologies. The end result is a suit that surprises for its consistency somewhere between the organic and the synthetic way. A synthetic way that seems to come from the future.
It is no coincidence that TIME Magazine has included her clothes among the 50 best innovations of 2011.
Her models are composed of different materials ranging from rubber to plastic. It's interesting the comment of the stylist about her "first time" with the prototyping:
The first time I used 3D printing, it completely changed my thinking. It freed me from all physical limitations. Suddenly, every complex structure was possible and I could create more detail than I ever could by hand.
Instead of depleting her creativity, prototyping expands it, opening new horizons. If this was possible in the field of fashion, why can't it could do in the area of cultural heritage?
The experiment to digitally document in 3D a statue of the Egyptian Museum in Torino (IT) was aimed to hardly test the potentialities of SfM techniques in archaeology.
The idea just came when I was visiting the exposition with my wife Kathi, during an holiday: I asked the guardians if it was possible to take photos and they answerd me that there were no problems as long as I was not using the flash.
As you can see from the picture below, I found a perfect situation when I reached the first statue's room; the athmosphere was charming, while the sculptures were in darkness, with only a spot light to make them stand out.
Spot light condition
This particular light condition was a good test for SfM techniques because I could not modify it "artificially" (e.g. with other lamps to get a better illumination of my subject). Moreover I could not use the flash, so I had to turn the ISO of my Nikon D70 to the maximum value, in order to be able to take pictures without the help of a tripod.
Another difficulty arose from the necessity to acquire the data quickly, without disturbing the visit of the other tourists.
The croweded room
Anyway, having increased the ISO of the camera, it was not a problem to collect all the data in just a couple of minutes.
Once home, I tried to do a 3D digital model with SfM and IBM techniques, using Pierre Moulon's PPT. Since I did not think to succeed in my purpose, I did just a fast 3D model, with low quality parameters (scaling all the pictures on a medium resolution). Contrary to what I thougth the model was accurate enought and the experimentation went on thanks to the collaboration of Cicero Moraes, who was able to recreate an high quality texture, using the methodology he described in his post.
The 3D low quality model in Paraview
CREDITS:
This article was possible thanks to the kindness of Dott.ssa Paola Matossi L'Orsa and Dott.ssa Sara Caramello and with the permission from the "Fondazione Museo delle Antichità Egizie di Torino".
The digitization of finds, as we saw in a previous post, has both advantages and disadvantages from different points of view. Leaving aside problems related to the economic sphere of the possible beneficiaries of their business (in the broadest sense), it is clear, however, that the technology that concerns the digitization has legitimized their use to a wider audience.
An audience that otherwise, perhaps by choice or particular socio-cultural conditions, would not get in touch with the same finds and, in return, to the sciences that study them.
The museum exhibitions and the educational exhibits are among the main beneficiaries of this new approach. It's a fact that an exhibition like Homo sapiens, which was held recently in Rome, would not have had the same impact on visitors if it had not made use of multimedia and interactive tools of a certain importance.
It is not just to amaze the visitor, but to help him to obtain, from its interaction with the exhibition, a real experience of the visit. Without this experience, in fact, hardly the visitor will reflect deeply on what he has seen and he will not derive useful advantage to his daily life. An advantage represented by an idea to be applied in his field of work, rather than the sheer relief given by the experience of beauty / interesting aspect.
The exhibition "Homo sapiens" is an example that can be misleading if we think, in general, to the usefulness of these technologies in the museum context. An example misleading because of the large investments and of spaces that were not the common ones.
Collaborating with local museums, I often deal with problems of exposure of the findings. The scarcity of economic resources that small museums often have to deal with and that basically is inherent to the very idea of a small museum (economic crisis or not) does not allow "easy" solutions that often coincide with high costs.
I recently reflected upon the relationship between technology and costs of the exhibitions, when I thought to the use of dioramas for a particular museum. The construction of models, when there is the possibility, is entrusted to specialized firms, sometimes to skilled artisans, more often to willing people who deal with it as a hobby and have a certain skill.
In this process, the technology is almost zero: the digitization and prototyping of models do not seem to be one of the basic tools to simplify the work of mounting. However, their potential is evident and the costs are relatively affordable, although it is to recognize that there is an objective problem of dissemination of this knowledge, which seem yet cabalistic material for the initiated few.
Build a diorama using rapid prototyping allows a considerable saving of time and costs, in addition to providing the basic material for the merchandising of a museum. If there is indeed a product segment that captures the imagination of the visitor is the object able to represent the visit just completed and that reminds him of the physical place where the visit took place (I omit here the anthropology of souvenirs which plays, however, its important part in this (re)cognition).
It's true that this process happens if the visit becomes experience and, therefore, as mentioned above, the visitor feels that he has acquired / purchased something applicable in other contexts. Therefore it's necessary, beyond the technological tools to be used, not forget that the visitor is at the center of everything, and that the finds in itself is only a means to educate him. “Education”, here, is not only the assimilation of information, but the opening of a new feeling about the topics covered.
So, without a good idea, the technology amazes without creating surprising experience, but without technology a good idea turns into a sterile list of information on a wall panel.
The link between idea and technology is in the experimental use (again, experience is the main part of the learning process and application) of the tools available, in a feedback process that goes from the idea to technology and vice versa. That is what has been experienced by our hominid ancestors with the feedback circuit formed by hand and brain, which created the language and has allowed both the biological and cultural evolution.
And the exhibits, in a certain way, are nothing more than a continuation of this process.
