Friday, October 7, 2016

Using Structure-from-Motion (SfM) for Rock Art

One of the coolest presentations from last week's URARA symposium in Delta was the one by Robert Mark and Evelyn Billo on using photographs to generate 3D models of rock art sites.  The technology is closely related to that used with Microsoft's Photosynth program which I wrote about in my blog a few years ago.  However, while Photosynth allows you to zoom around and view a site from the point of view of each camera shot, the tools that Mark and Billo were talking about allow you to actually reconstruct the site as a 3D mesh and overlay the information from the photos as a texture using the same technology.  This is really cool.

Pictograph Panel on Black Rock Mesa
To test this out, I took a series of photos of the boulder above which we visited on the Monday URARA field trip.  I got it from three or four different angles and shot it in close up sections.  I then input these images into two programs.  1) Agisoft Photoscan, which is the program that Mark and Billo talked about at the symposium, and 2) Autodesk ReMake, which I found online.  Photoscan has a free 30-day trial and seems to generate better results, but it costs $179 for the basic version.   ReMake runs the analysis on the cloud and can be much faster, but costs $30 per month once the trial version expires.

Below is a clip of the model that ReMake generated in the form of a quick movie.

The Photoscan-generated model can be viewed at this link.

Here are the same photos at Photosynth.

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