|Laser scanning a sauropod vertebra|
|Photogrammetry of an Asian elephant from Falkingham, 2012.|
Scanning and image segmentation
|Swiss Light Source synchotron - the giant ring at the front, but all the other buildings are associated|
|Piece of pliosaur jaw in Southampton CT scanner. Went on to be published in Foffa et al. 2014 (x2) with which I was involved.|
|CT scan demonstrating the god awfulness of fossils in matrix. Blue is toothy bits (mostly), although there is lots of noise in the image, whilst the red area is my deselecting pixels.|
The complexity of the process is often determined by the preparation of the fossil (more matrix makes segmentation more tricky), the x-ray density of the fossil compared to the matrix (e.g. where bone is more x-ray opaque than the matrix there is clearer delineation between the two), the type of matrix (iron or pyrite rich matrix, for example, tends to make it tricky for good CTs to be made), how well scanned the item was/number of artefacts.
Using these digital preparations is becoming more common to guide the actual preparation of fossils in large museums where CT scanner access is now easy. Another thing the virtual reconstructions allow is retrodeformation (basically the undoing of damage suffered whilst the specimen is fossilised). Stephan Lautenschlager has been incredibly good at it, and I have a paper in review at the minute discussing my experience so stay tuned!
The resulting reconstructions can then be used for publication, or exported in various formats (commonly .stl or .ply) to create 3D pdfs, create 3D printouts or use in functional analyses. There are some good .stl repositories for fossils e.g. Phenome10k.org that allow of exchange and sharing of models.
|Let's be honest this is cool, and you kind of want one.|
3D pdfs - This is much like 3D printouts, except in its digital format that opens with most Adobe Readers. 3D pdfs allow for users to gain access to reconstructions, and in the highest quality ones can allow users to interact by removing components (often things like soft tissues from around skulls). Again these have the ability to be rapidly sent to collaborators worldwide, but they also allow for more detailed figures within publications to allow for better understanding of features that are being described. If you are unsure of what I mean, please do go check out the Witmer Lab's work as they are one of the main users for both scientific and outreach purposes.
|Shamelessly taken from my own paper on spinosaurs: (A) When a load is applied to a beam with one fixed end (a cantilever beam), the effect of the beam is a deflection in the direction of the force. This results in the most extreme tension on one side of the beam, and the most extreme tension on the opposite side. In the middle, there is a point where there is no tension or compression, called the neutral axis. B) Two circular cross sections of equal cortical area (black). Beam theory states the solid tube (hollow circle) will have higher resistance to bending and torsion than the solid circle due to the material being distributed further from any neutral axis. DOI10.1371/journal.pone.0065295.g004|
FEA - See the earlier blog post I did for lots of details.
|T. rex model with all of the muscles attached to the limb and pelvis, from Hutchinson et al., 2005|
|Stegosaurus convex hulls. From Brassey et al., 2015|
So that wraps (pun definitely intended) up some of the methods we use and why we use them when it comes to palaeontology on computers. Most of these methods are less than 20 years old. Just imagine where we will be in the next 20!