Tag Archives: 3D modelling

Fun with SFM – part II: The results

So, hello, dear all, I am back from a very busy family weekend – and I would like to entertain you now with our second part to our SFM-tutorial!

Due to my work at University, I have the opportunity to work with Agisoft Photoscan, which is quite the same as Agisoft Metashape. You can find all the information on this software here – I am very used to it, it is very easy to work with, very easy to understand and you hae all the features collected in one software. Of course, there are other softwares, even a lot of freeware for 3D modelling – I used to work with them as well and I think, the next step will be a comparison of the different softwares by modelling the same object. I am just looking for the time to do it, because: My dissertation has to be (okay, should be) finished by December… so, time is really rare in my life right now…

But this post is all about my little Eros/Amor riding his hippocampus. You can find the information on this example here in my first post.

I opened Agisoft Photoscan and loaded all the images I wanted to use meaning all the pictures I have taken. The first step is the aligning of the images. The software searches for the same points on different photos and matches them.

Step 1: Aligning the photos
Step 2: Building the point cloud

The next step will be the point cloud – of all the points that the software could match on different photos (the best thing is that you get the same point at least out of three different directions) there will be a so-called point cloud as a result. As you can see in the second pic here, there are a lot of “noises” around my object – you can barely recognize Amor’s foot an the tail of the hippocampus.  So, the next step is to clean this mess up. You just mark all the noises around your object and delete it. Another possibility is to mask your photos before aligning them and starting to build a point cloud. Either step will take its time.

In my first post I mentioned the different directions you have to take the pictures from. Here is a screenshot of all the thumbnails of my pics, just to help you geting an idea.
And again, the front view of my model, here already “meshed”.

So, after cleaning you will get a very nice point cloud showing just your object. I just took the side view of this sarcophagus, so my object remains quite flat with no other sides.

After the last step – the finished model!
In detail and without texture the model consists of a grid that connects all the points with each other and gives the actual shape of the surface.

After building the so-called dense point cloud (you may notice the features of the relief getting clearer), we can start with the last step – to build the actual model. As you can see here, I really tried quite hard with the texture as well. The texture can be build out of all the coloring information you have in your pics. This step is not necessary, if you are just interested in the shape of the surface. Therefore, you will get better results without coloring your model, because your eyes might get betrayed by all the shades and colors.

If you want something nice to show your students or your friends, then go for the texture. 😉

Of course there are further things to do on Agisoft Photoscan/Metashape or with other software – it’s a playground, so feel free to try. And remember, I took these images with my phone camera, so no pressure on that. Of course, your first tries may suck, but hey, it’s a process. I am still learning too and I am still discovering new fascinating features and possibilities.

I hope you enjoyed this little post – stay tuned, keep calm and start 3D modelling. 🙂

All the best,

Astrid

Fun with SFM – Part I: taking pictures

So, welcome to our first tutorial on SFM – structure from motion to get a 3D model of your favourite object. In our case, due to our name “Epigrammetry” which combines Epigraphy and Photogrammetry, we would like to start with a stone. Actually not just a stone, it is one side of a sarcophagus placed outside the church of San Canzian d’Isonzo in Italy. I choose this example because I do not need any permission for taking pictures there – and using those pictures for our turorials online.

If you would like to follow our instructions and you have choosen a certain object for it, please always make sure that you are allowed to take pictures and to use them. In most cases, you are allowed to photograph objects, but you are not allowed to show your results online or to publish them, so this is the tricky thing you have to be aware of.

In this first part we will concentrate on taking pictures for your model. You will not need a high professional camera – use your smartphone, because this is enough to start with the basics and getting a feeling of the process.

1. The light – when taking pictures, always consider the light!
Is it sunny, is it cloudy, has your object any shining surfaces? For 3D modelling, all this things are important.
The best weather – if your object is placed outside, like mine is – is actually a cloudy day. The light will be consistent on your object and this will give you the best results, especially if considering the texture (the colours of your real object that you want also on your model). If there are some too dark spots, your camera may not be able to handle them, so it is lost for the software, because you cannot get any points out of it.

2. Keep about the same distance to your object – at least try! I know, this can be sometimes really difficult, but your results will be better. Also, try to keep exposure and focal length the same while taking your pics. And you will have to do a lot of them. For our example here, I took about 70, which is okay for a very rough model, but a quite good one.

3. Move! You have to move the camera. By this, I mean you have to take your pics step by step. Always let about 60% to 80% of your pics overlap and never stand still an just turn the camera in different directions. At least, if you annot move your feet, move your torso and the camera to another position. Yes, this can be very funny for your spectators. 😉
So, just keep in mind: Overlapping and moving!

3a. If you have a small object and you want to get every side, never move the object! It won’t work! You will confuse the software. If you have to move the object, you have to do different models of every side and then you have to bring them together with the help of Meshlab or whatever program you want to use.

4. Try to get every pic of your object out of at least three positions. Help yourself by following the surface of your object with your movements – at least, this works out for me and the stone reliefs. For a frontal and flat object, try to take pics from different positions and angles.

5. Keep a list. If you have to take a lot of pics for different models, keep a list of your pictures by writing down their numbers in line, the object, the side, the date. You will definitely get confused, trust me. 😉

6. Always do a back-up. And yes, please, save your data immediately! Do a back-up. You know why. 🙂

Of course there are other very good tutorials on photogrammetry 101 on the Internet and I myself learned a lot by reading and watching them.

We will catch up with our little project when I am back from my holiday!

Stay fierce!

Astrid

London calling …

Workshop on Digital and Practical Epigraphy
(London, April 29–May 4, 2019)

As you might have seen on our Twitter or Instagram-Account, I spent a week in London, participating at a really interesting workshop. It caught me while flipping over some homepages on epigraphy and classics in february this year. I was working on my catalogue for my thesis back then and somehow really frustrated about the fact that some archaeologists have no idea about epigraphy at all. Well, there are also some epigraphists who do not think inscriptions are archaeological material either, … So, it is time that we change this view, don’t you all think so?

I want to show my network and the people around me that (mainly) stones with letters on them are far more interesting than any epigraphist or archaeologist has ever thought of before. And because of that I decided that it is time to show the world my fascination. And as an archaeolgist, I use pictures for sharing my research, before I use words. And, good thing for me, this workshop was actually on taking pictures of inscriptions – or, so to speak, different methods to produce images and/or a proper documentation of inscriptions.

So, what did I learn at this particular workshop?

We started with the various methods of documenting inscriptions. And we really started from scratch, talking about the method of making squeezes (basically pressing and smashing wet special paper on a wet stone by using a great brush – acutally you can watch a video on how to do it here), about taking drawings of the inscriptions and so on. We talked about printed epigraphic ressources as well as about online sources.

We had a very interesting introduction to photogrammetry as a method of documentation for inscriptions. We tried it out at the wonderful St Pancras Gardens – next to making squeezes, we had to pick one stone of our choice – I decided on a little broken one who stucks in the earth and has a pretty angel face on it. We took the photographs wth our smartphones. This was completely new to me, for I am used to my DSLR camera – but I was very surprised to see my results after the whole aligning, dense cloud building and mesh building on Agisoft Metashape (looks quite the same like Photoscan, does the same, feels the same – at least for me).

As you can see, it does look really nice…

After our work with 3D-models and squeezes, we got into the “serious” DH-stuff… I am talking about TEI, EpiDoc and EFES (EpiDoc Front End Services, which is a custom and a platform for publication and search/indexing of EpiDoc files). I have heard the terms “TExt Encoding Initiative” and EpiDoc before, of course, I knew that there was something about coding and tagging and XML, but how all these things are really connected, never ever came clear to my mind, because I simply never ever had the time to read through the amazing amount of information on these things.

Basically, it is a way to encode your inscriptions with all the metadata and information you have about them (e.g. finding spots, description, the museums where it can be found today, transcription etc.) in XML and to make them accessible online on a database or website of your project. There are many different projects running on these kind of scheme, just scroll through the short Wikipedia entry on EpiDoc and click on the various links!

Coding means “keep the cookies coming” – and thank God they had really tasty cookies there. And coffee. Now I finally understand all my friends who work as programmers…

The people behind EpiDoc which gave this workshop are very interested in getting people to know about their project and sharing their knowledge on how to get inscriptions online to make them accessible and useful for science and research to happen. So, go ahead and inform yourself on the various possibilities of participating at a workshop where you can learn the basics of EpiDoc!

… and EFES, of course. This is one of my first tests with EpiDoc files I had to run on EFES, and it worked – it may not look that aesthetic, but, hey, it worked out the way I wanted it too!

By the end of the week, I have to admit it, I was really exhausted. There were so many new things criss-crosing in my mind, it took me nearly four days to recover my brain… For now, I am busy trying to summarize my notes and to work them through again, just making sure not to forget anything important. I hope that soon I can find the time to write more extensive posts on the single methods I learned about.

For now, it is just a very short summary on this amazing week.

I hope you enjoyed this little overview –

take care!

Astrid/archaeogirl