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 short post is to share the presentation we did yesterday in the "Accademia di Agricoltura, Scienze e Lettere" of Verona. This presentation is part of a bigger project in which we were involved by the Cultural Association Archeonaute.
Basically we have been hired to enhance two archaeological sites in Verona: the Roman Villa of Valdonega and the ancient Capitolium, which is now under the medieval Corte Sgarzerie. I will write later about the whole project, since the presentation of yesterday was focused on a single phase of our work: the 3D reproduction of an unique archaeological find, the so-called "Catasto A" (a Roman cadastrial bronze tablet).
Here below is the video, I hope it can be useful for someone. Have a nice day!
PS
The video by now is just in Italian, but if someone want to help us in adding English subtitles, I let this possibility on YouTube.
As you probably noticed, one of the topic of ATOR is related with hardware hacking, with the aim to build new archaeological devices from ordinary objects and tools (33).
This concept is close to the one of "reuse" (using an artefact for a purpose which is completely different from the original function), a pretty common phenomenon in archaeology; also in architecture there is something similar, called "spolia" (but maybe our interest in hacking things is just a kind of McGiver syndrome of people grown up in the 80s).
However, this post is about hacking a common game device like Kinect to use its characteristic in archaeological 3D real-time documentation. If you are a regular reader of ATOR, you will know that we already face this challenge, performing a first test (1) with RGBDemo in February 2012, and controlling accuracy and precision of the device in March of the same year (2), after a discussion with some of the researchers of FBK, during the workshop "Low cost 3D: sensori algoriti e applicazioni". Due to the encouraging results achieved in our first experiments, we worked on the hardware in order to modify it for outdoor projects (3), but soon we experimented the limits of this technology when applied in areas with direct sunlight (4) or in documenting small objects (5, 25). Despite this drawbacks in our research, Kinect worked pretty good in indoor excavations (6), helping us in difficult situations (related with the the workplace safety), and for particular purposed, like for infra-red prospections in dark environment (7).
After all these experiences, our final advice about Kinect is that the device has a potential in archaeology, but its real employment in professional work is restricted to peculiar conditions, while in most of the cases the SfM-based techniques are the best option (due to their versatility, which makes them a perfect choice during missions abroad (8), for small finds documentation (9, 10), for underwater and aerial archaeology (11, 12, 13), considering also the speed which characterize SfM and MVSR open source software development (14) and the wide range of possibilities between the different tools (15, 16).
Well, at least this was our opinion until now... Currently we are changing our mind about Kinect, and this is due to our professional engagement in underground archaeology (17) and to our renovate interest in robotics. Let's deal with these two points separately.
Underground archaeology
Documenting an underground semisubmerged structure in Firuzabad (Iran)
Like any other operation in archaeological 3D documentation, the tolerance regarding accuracy and precision is variable and influenced by some factors, and mainly: research purposes, logistics, characteristics of the structures to be documented.
Without considering some important exceptions (e.g prehistoric rock shelter, which are often simple to document with SfM techniques), most of the structures related with underground archaeology (WW1 artificial caves, medieval mines, etc...) are connected with large scale survey projects (where it is important a "big data" approach, raising the tolerance in data acquisition to increase the number of documented structures); with logistically difficult areas (high mountains, glaciers, (18, 19) etc...); with structures often characterized by vast surfaces without important small details, which (when present) can be recorded with a targeted SfM or RTI (21, 22) documentation (e.g. for graffiti, inscriptions (20), manufacture traces, etc...). For this reason, in most of these projects, it is necessary to deal with precision in documenting (keeping checkpoints thanks to other TOF instruments, like total stations) in order to gain a real-time response from the selected device, and, under this point of view, Kinect is often a good solution, considering also that its infrared sensor helps very much in low light conditions (7).
Documenting WW1 caves in Southtirol (Italy)
Archeorobotics
Arc-Team's UAV during an aerial archaeology project in Storo (Trentino - Italy)
Since 2006, when we joined an aerial archaeological project in Armenia (23), we started to work on "archaeorobotics", trying to develop robotic devices able to help us in the most difficult archaeological missions.
The first positive results we reached in this field were related with aerial archaeology and the building of an open hardware UAV (in 2008), even if at the beginning we underestimated the time needed to practice with our new tool (24). Soon our experience increased as we built different drones, based on open and closed solutions (like kk multicopter (26) or Naza dji (27) models). The benefits of this research branch were clear (28, 29) and soon other research institutions, like the CNR-ITAB of Rome (30), the University of Lund (31) and the CNR-ISTI of Pisa (32), asked us to give lessons about this topic.
Another field of archaeorobotics we explored is the one related with CNC machines and especially with 3D Printers. For this topic a precious help came from the society Kentstrapper and Leonardo Zampi (aka +Exekias 87), who helped us in 3D printing the cast of the Taung Child (34, 35). Since RepRap project started (in 2005), 3D printers evolved very fast. Of course our interest regarding these machines is mainly oriented to Cultural Heritage, and this is also the reason why we built a Fa)(a 3D form scratch (36), but results with this kind of instruments can be very impressive, especially considering the wide range of scientific applications (37, 38, 39, 40, 41), even if sometimes you have to deal with difficult boolean operations (42).
However, none of the robotic projects we developed till now needed Kinect, being based on UAV, to 3D document archaeological sites, or on CNC machines, to fast replicate archaeological artefacts. Our renovate interest in Kinect for archeorobotics is due to our new challenge in developing a ROV (Remotely Operated Vehicle), in order to assist us in our underwater archaeological missions. Indeed, in the last months, we started a collaboration with the WitLab, the FabLab of Rovereto (Trentino - Italy), to develop a new Open Hardware ROV, especially designed for archaeological aims. One of the main topic in developing such an instrument is that the new robot will be oriented not only to 3D documentation, but also to the exploration of unknown areas. For such reason SfM and MVS software are no more enough, but we had to start again in testing Open Source SLAM (Simultaneous Localization And Mapping) algorithms, due to the fact that we need to register in 3D the submerged landscape (Mapping), but also to recover the path the "ArcheoROV" did (Localization) to reach new hidden archaeological evidences (for a better planning of human operations).
Testing the ArcheoROV at night
Testing Open Source SLAM solutions
The importance of SLAM algorithms in exploring devices is the main reason why we started again to experiment Kinect. Indeed, despite Kinect cannot be used as an on-board optical device in our ArcheoROV (due to the infrared camera), this tool is the perfect system to check SLAM software.
If, you ever started in working on robotics, probably sooner or later you stepped into ROS (Robot Operating System), an Open Source (BSD License) collection of software frameworks for robots. Of course SLAM is a very important task for any robotic vehicle, and the ROS package RTAB-Map is a perfect solution to implement this capability into any autonomous or remotely operated machine, like our ArcheoROV. For this reason, before starting experiments in more sophisticated (and complicated) systems, we checked RTAB-Map performance with an old Kinect, and here is the video of the result:
As you can see, the performance of real-time 3D is pretty responsive, respect our old experiments with the Open Source software RGBDemo (also considering that the Kinect used in this video is the first version, and it is now pretty obsolete) and, most important, the localization function within SLAM algorithm works very good. As I wrote at the beginning of the post, our current impression is that this combination of hardware (Kinect) and software (ROS) can be a good solution for underground environment documentation, while the software can be the right choice for archaeological exploring robotic devices.
I hope that this long post will be useful, if you have any feedback, please just write your comment below. Have a nice day!
PS:
we will present the ArcheoROV at the ArcheoFOSS (43) of Cagliari (Sardinia - Italy), this year. Also our partner of WitLab will be with us!
The reconstructions of the faces of hominins; of St. Anthony and of the Blessed Luca Belludi; of Francesco Petrarca and of Giambattista Morgagni, are the evidence of a research that lasted for months and that continues nowadays; a research intended to be expanded to other areas of interest.
In fact, the exhibition offers to the visitors the opportunity to reflect on concepts meaningful to anthropology as diversity, self-perception and identity from the point of view both historical and contemporary, but it is also a mirror of a continuous testing of technologies that open new perspectives in different areas of anthropological research.
Staying in the wake of the topics of the exhibition, there is no doubt that the perception of the self and diversity are important parameters in the assessments of medical anthropology, especially if the feedback on them are carried out in the light of the implementation of new technologies and 3D printing, in particular applied in medicine.
For example, the prostheses that can be constructed, even printed, in a relatively short time and custom-made for the patient. We have a lot of examples from this point of view: the mandible custom-made for a 83 years old woman or the cranium completely replaced in a 22 years old Dutch patient; or the realization of live organs, such as liver, tracheal cartilage and ear directly using living cells.
More, forensic reconstruction is a valuable tool in reconstructive surgery: examples of implementation, in this context, are the reconstruction of the face of Albert of Trento via open source software, or of the face of a child mummy preserved at the Saint Louis Art Museum.
I shall focus in particular on an implementation made by Cicero Moraes in order to treat the developmental dysplasia of the hip (DDH), a neonatal congenital malformation and treatable using Pavlik harness or making a particular plaster cast (hip spica cast). There may be, in severe cases, even a type of orthopedic surgery.
This treatment involves a continuous monitoring of the patient because of its complications: pain, increased temperature, lesions of the skin. Moraes, together with researchers Munhoz, Kunkel and Tanaka, has implemented an alternative method to the common orthosis consisting in a photogrammetric scanning of the hip in order to replicate the perfect geometry of the anatomical part, with reduction of costs and time and avoiding complications to the patient.
The aims of our research are gradually expanding and we know that we have to do still a lot of work. It's a good thing, however, that we stopped for a moment to take stock of the situation and to recognize that we are helping to improve the state of affairs. Not only in archeology and anthropology, but also in other fields thanks to the scope of what we are doing. A result achieved thanks to motivated individuals who, despite residing in geographic areas far apart, have joined efforts to reach a common goal by sharing data and projects.
since last year we are working on the preparation of the open source exhibition "FACCE. I molti volti della storia umana" (here some news in ATOR: 1, 2 and here the official page and the FB page). Of course all the software we are using are Free and Open (FLOSS), but for some particular exhibits, we are working also with open hardware.
Our interest in this specific topic dates back to 2006, when we started investigating the potentialities of open hardware in archeology, especially in the field of aerial photography e rapid prototyping. We get the first results in 2008, with our UAVP prototype (here some news from ATOR: 1, 2) an all the other UAV we built (KK, etc...).
For the exhibition the main open hardware we used are 3D printing machines. We experienced different solutions: +Leonardo Zampi printed the 3D model of the Taung Child thanks to the Kentstrapper machines, an ideal choice if you want an hardware which is ready to work out of the box (here the related articles: 1, 2)...
The Taung Child printed in the Volta printer (Kentstrapper)
One of the main issue in 3D printing for Cultural Heritage is to replicate an object in the right scale (otherwise you will just print a souvenir) and this is why it is very important to know how to perform a 3D scan, but also how to post-process your data ( (in ATOR you will find a lot of informations about this), in order to send the right file to the machine.
Here are some example of the models we are printing for the exhibition (scale 1:1): some 3D skulls of hominids (different individuals of Homo georgicus) we were able to scan, tanks to the kindness of Prof. David Lordkipanidze, during our mission to Tiblisi and Dmanisi. We will use them to prepare some Augmented Reality interactive exhibits related to paleoart.
3D printed skull (side view)
3D printed skull (front view)
And here is a short video of our Fa)(a 3D in action:
Some weeks ago Luca Bezzi wrote an interesting post about conversion of a grey-scale image into a 3D printable .stl file, using Free Software (i.e. G.I.M.P. to convert the image and Blender, with the "Image as plane" addon). Here is a video-tutorial:
This method can be used for any image, but it is particulary useful to create physical model of terrains; in fact Luca Bezzi took inspiration from topography, as he explained in comments.
Anyway, today there is a faster and more precise method to do the same thing, as reported in Impresoras3d.com; a web-app, called Terrain2STL, that can can convert a Google Map into a 3D printable file. The app has been created by ThatcherC, is Open Source and available on GitHub.
Terrain2STL is very easy to use. You just have to type http://146.148.78.19/ on your browser; you will see a physical Google Map, and, on the right, some tools. Once you have defined the area you want to print, you can click on "Center to view" to set the center of the area (a red rectangle) on the central point of the screen. Then you can adjust the dimension of the area using the line called "Arc Second/Division". Once you have set the area, you just have to click on "Create .stl file".
A limit of this app is that you can not draw an area crossed by a grid line (in this case you will see an error message: "Something went wrong: you may be spanning a grid line"). Anyway, this problem can be easily solved dividing your area in 2 parts and saving them separately.
Opening the generated .stl file with NetFabb Basic it may happen that the danger symbol appear, because the 1st time the software may not be able to define the volume of the object; however, you can just click on the "automatic repair" button (the red cross) to easily solve the problem, and have a clear file.
When you start a new research you know where your path begins, but you do not know where it will end (and where it will take you).
As many of you knows, we work also with 3D printing of archaeological objects: here (1 and 2) is the two post +Leonardo Zampi wrote about the Taung Project and here is a post regarding some Augmented Reality applications, in one of which a 3D printed skull was used (look the first video).
Most of these experiments are connected with the open source exhibition "Facce. I molti volti della storia umana" (please, do not forget our crowdsourcing campaign: send us your images!). For this event, whose English title is "Faces. The many aspects of human history", we planned to used 3D printed objects for different Augmented Reality applications and to expand the accessibility to the digital exhibit for the visitors (reducing the restrictions connected with disability). This post reports an preliminary overview of the event (done during the European Academic Heritage Day 2013), in which are presented the main topics of the exhibition, the problems and the solutions we planned to apply (sorry, the slides are in Italian; I will translated the text ASAP).
Today, working on a new research for this exposition, I tested different possibilities to reconstruct a 3D from a unique image. Normally our (Arc-Team) work-flow starts with a 3D model obtained from Structure from Motion and Image-Based Modeling (using different software) or from x-ray Computer Tomography (like for the paleoart or mummiology projects), but in archeology can happen to use Single View Reconstruction techniques when there are no other solutions. This post of +Cícero Moraes is a good example of a reconstruction in Blender based on perspective and vanishing points. Of course this technique is optimized for architectural documentation of structures, but is almost unusable for more irregular objects.
To avoid this problem I studied different possibilities and I decided to use the same software, Blender, but in a different way. I looked in internet for an archaeological picture that could meet my requirements: not too simple, but with a correct light exposition. My problem in finding a good base image comes from the fact that the archaeological artifact photography has codified rules and normally the light source is located in the upper-left corner, otherwise bas-relief (convex) would appear as counter-relief (concave) and vice versa (due to the Hollow-Face optical illusion).
After a while I found this image, which has an almost correct light exposition (sorry, I do not know anymore the source of the photo and I did not find informations about the author).
The base image
I modified the picture with GIMP, in order to obtain a grayscale photo, than I imported it in Blender.
The grayscale image
There I used the "displace" modifier and I automatically obtained a fast 3D of the object (of course nothing comparable with SfM and IBM technique, but enough for my SVR needs).
The displace modifier
After some additional smoothing operation in Blender (you can directly use the related modifier), the model was ready to be saved as an stl file, loaded in Cura and printed in 3D.
The stl file in Cura
At this point I was ready to adapt the entire process to my needs in order to work for the exhibition "Facce", but here is were my research took a complete different way.
On my desk was lying a local newspaper in which was a photo of the Italian astronaut Samantha Cristoforetti, who is actually on board the International Space Station (ISS). Dr. Cristoforetti was born in Milano, but her family is originally form a town (Malé) very close to the one in which I live (Cles) and this is the reason why local press is following her scientific mission very closely. Reading the article I was thinking that it would be nice to print in 3D something that could be a tribute to her work and to the whole mission: something related with space exploration and archeology. Suddenly in my mind appeared a black and white picture, which probably most of you know and that dates back to July 20 1969, so I decided to test the process on this image and see the result.
I searched on the NASA website regarding the Apollo 11 mission and I found what I was looking for: the photo of the first footprints on the moon. I turned the picture into a grayscale image and I repeat the protocol of Single View Reconstruction with this data
Of course the result has no metric, nor topographic value and it is more an artistic reconstruction than a 3D documentation, but this time it was just for fun and for a tribute to woman's contribution in space exploration. BTW on board the ISS astronauts are currently testing 3D printing in space (Made in Space).
If you want to print directly the .stl file I did, you can download it at this link. Otherwise in this post you can find all you need to do the process by yourself.
As Luca Bezzi said in his presentation in Catania, the next step in the Taung project was 3d printing; in a previous post, I explained some issues we found in the original mesh. But thanks to Cicero's suggestions, the problems have been fixed, and 3 days ago Kentstrapper finally printed the Taung Child skull.
Here are some images:
The .stl model
Kentstrapper strongly believe that 3d printing can be a real revolution in education and culture. And, of course, in archaeology 3d printing should also be a great change in museum expositions: facial reconstructions, scale models of ancient buildings or (as in this case) plastic copies of finds could make archaeology much more easilyunderstandable for visitors.
HERE you can download the final .stl file of the skull.
Some
weeks ago, Arc-Team and Kentstrapper
(a Florentine startup that produces 3d printers) decided to
collaborate, in order to make the Taung
Child 3d model real, and possibly expose it in a museum.
But
how does a 3d printer work exactly?
Basically
a 3d printer uses the FDM (Fused
Deposition Modeling) technique, an additive
process where successive layers of
material are laid down in different shapes; following a digital model
of the object, the printer deposits layers of plastic material,
automatically fused to create the final shape.
So,
what we need first is a .stl model of the object. But (for now) not
everything is 3d-printable: some spefic characteristics
are required to be printed.
Which
softwares can be used to locate and fix problems?
The
most used software is Netfabb,
that is not
open-source neither free, but
Netfabb
Studio Basic
can be freely downloaded.
In
the Open-Source world, we can obviously use the 2 main 3d modeling
softwares: MeshLab
and Blender. In particular,
in
version 2.67 of Blender a
3d
printing toolbox
has been inserted as add-on: it's useful to check the
mesh and see
which are the problems. Pressing
“Check All” a complete scan af the mesh will be done.
Volume:
the
mesh must be solid. It
cannot have holes, 2-point polygons or single sided polygon
surfaces.
Mainfoldness:
the mesh must be completely and perfectly closed. The
mesh must be “2-mainfold”: every edge must belong to 2 faces
(not 1 or 3: only 2). Here are some reasons why a mesh cannot be
2-mainfold:
Holes:Automatic
hole-fixig can be made with Meshlab (Edit-Fill
hole)
or Netfabb;in
Blender,
from version 2.63 just selecting the vertices that “compose” the
holes and pressing F in Edit Mode the missing face will be created.
T-Edges:
an edge cannot be on a board. In this case, the volume is considered
open, even it seems closed. The face must be deleted and rebuilt
(with the same method for closing holes).
Internal
faces: internal
faces must be deleted, because they make the mesh “3-mainfold”.
Minimum
wall thichkness:
tipically a wall thickness of 2.5mm is required. The
Blender toolkit can show the too-thin areas, that must be scaled
till a proper dimension.
Polygon
number:
with too few faces the figure will lose detail, but with too many
faces the fill will be heavy and possibilities of error will
increase. To reduce the number of polygons of a mesh we should use
MeshLab, following this
tutorial.
Intersected
faces: there
may be 2 or more faces intersecting themselves,expecially
in objects composed by two or more meshes. Even in this case, a
solution should be remove the intersecting faces and then closing
the hole with the method said.
Zero
volume faces/edges: faces/edges
with no volume.
So,
here
you can find the .stl file of the mesh. It's a really complex mesh,
with an enormous number of faces and several problems (thickness,
distorted faces); our goal is making it 3d-printable, and that's why
we ask for your help.
P.S. Thanks to David Montenegro for his suggestions.
