3D Geometric Morphometrics of Projectile Points – Populating Splines


As we continue to think through the various spline configurations (see previous post here), I have been constructing a number of models based primarily on the efforts of previous analyses for both 2D and 3D geometric morphometrics. While this is representative merely of a (very) humble beginning, experimenting with the reconstruction of configurations used in other analyses could help us to better understand how we might begin to move toward a replicable consensus configuration (certainly some great examples out there).


In this example, I am using the framework of two splines that were created as a 3D mesh sketch in Design X (above). I then added 10 equidistant sections (below) between the top and bottom of the projectile point. While those would most likely be cut where they intersect with the splines above prior to populating point data, I wanted to see where the–equidistant–points would populate along the various profiles.


In this case, it may work best to cut each of the 10 sections where they intersect either the exterior or interior profiles (or both), prior to populating the LM/sLM data. I did not populate the 10th section (very near the point of the projectile) for this example, simply because it was almost impossible to view the location of Point 2 (which is defined by the confluence of the vector and the poly-vertices of the mesh at the tip of the projectile) when that particular section was populated.


Another question that we will need to ask ourselves sooner than later, is where do we reach a point of saturation or diminishing returns with regard to the number of LM/sLM data points? There is still much left to think about, and we will continue to move toward the definition of a replicable consensus configuration as we work through replicating (as closely as possible) the numerous configurations that have been used in the past.

Our tactics differ from many of our colleagues, due primarily to our efforts to devise a configuration aimed at performing an initial “sort” at the assemblage level–different configurations would then be used for each of the identified categories based on more specific attributes. In the coming months, I hope to share some of our minor successes, and–no doubt–numerous failures as we continue to work toward a suitable configuration.

As always, your comments and constructive criticisms are welcome. You can comment by clicking on Leave a Comment below, or you can email me directly at selden3d@gmail.com. 



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Written by zselden

Selden (PhD, Texas A&M University, 2013) is a US Marine Corps veteran, cyclist, kayaker, backpacker, hiker, climber, fisherman and general all-around outdoor enthusiast. His research is focused at the confluence of archaeological methods and digital technology, and he is particularly interested in the application of 3D technologies to archaeological problems, geometric morphometrics, network analyses, predictive modeling, archaeological theory, and archaeological science.