Greetings! My name is Beau Kromberg and I’m an archaeologist moonlighting as a self taught 3D content creator. In the four short years that I’ve been working with photogrammetry, I’ve been part of a number of projects that highlight the diverse ways that 3D technologies can be used in archaeology. This work has included solar simulations of Incan carved stones, building 3D models of archaeological sites, and making interactive software experiences. My background in 3D capture and modeling has been self taught through reading articles, software documentation, and watching online tutorials, so if you’re thinking that digital heritage development requires fancy equipment and formal training, I hope I can convince you otherwise!
My first foray into the world of photogrammetry was watching video tutorials on YouTube by Samantha Thi Porter, a digital curation specialist at the University of Minnesota, who has made a video series explaining her basic workflow with Agisoft Photoscan (now MetaShape). After understanding the basics of the process, I needed to come up with a project to experiment with, which got me thinking about the different ways that digital objects can be used in archaeology. When doing analysis of artifacts in a lab, archaeologists often use comparative collections to identify objects, but don’t have access to them when they’re out in the field. So what if you could take those comparative collections on the go? This resulted in my first 3D capture project, which was a digital comparative chert collection that could be used in the field to determine the type of stone that a prehistoric tool was made of.
Solving Problems with 3D Applications
After having a general grasp of photogrammetry, the focus of my research at Wayne State became exploring different ways that 3D technology could be used for public outreach in archaeology. The Gordon L. Grosscup Museum of Anthropology houses a large number of collections from around the globe, including artifacts that have been recovered by Wayne State students during archaeological digs in Detroit. Although these collections are extensive, the physical space of the museum is limited and many artifacts may never get a chance to see the limelight of the exhibition hall. As a response to the physical limitations of museums, my recent work has been investigating ways that digital technologies can be used not only to make museum collections more accessible, but also how these technologies can be used to share the experience of archaeology with everyone.
One solution that our museum came up with to cope with the limitations of exhibition space was to develop an augmented reality application that allows visitors of the Grosscup Museum to view 3D models of collections that are not currently on display. Programmed using Unity and Google ARCore, the “Magic Cabinet” software lets users search for artifacts, and then visualizes them in real space with a mobile device. The software uses AR image tracking to locate photo markers that have been placed inside of the physical cabinet’s empty drawers, which then generates the digital artifacts in 3D space. The artifacts can then be selected to get more information, and inspected using swipe gestures. This solution allows the museum to keep a limitless number of digital artifacts on permanent display in a small space while the primary exhibition continues to rotate.
Approaching 3D Capture Scenarios
Working as a graduate student with budgetary constraints, my 3D capture methods have always been a result of what hardware was available at the time, and subsequently I’ve found that robust 3D models can be generated with everything from DSLR cameras to cell phones. When building artifact models I use a homemade turntable built from 2 pieces of wood and a lazy susan bearing, with black velvet attached to the wood for photo masking. Using a printed photo mat that depicts degrees of rotation around the turntable, photo capture can be conducted by keeping a camera stationary while rotating objects on the turntable a set number of degrees. The portability of this setup makes 3D capture of artifacts accessible in both field and lab settings.
There are a number of ways to go about photo capture for photogrammetry, and I’ve found they all come with their strengths and weaknesses. In general, having more photos will yield a better result, however, objects that have a large number of holes or openings frequently require manual photo mask editing. So although having more photos yields better results, the amount of time masking photos will increase, and the overall runtime of a project will also increase. Similarly, adjusting shutter speed and aperture to make black background materials more uniform and easier to auto mask comes with the caveat of the object appearing darker. My personal preference is to adjust lighting to achieve a uniform background, and take photos at 3 heights every 10 degrees, for 108 total photos. If the artifact looks too light or dark, the photos can be adjusted in Photoshop or Gimp after the masking, or the object texture can be adjusted after building the model.
For capturing large archaeological sites and features I’ve found that the most useful approach is to break capture sequences down into multiple photo sets with overlapping photos. This allows each segment of the model to be run individually and aligned later, or built as a whole all at once. If a portion of a model is not building out to an acceptable quality level, that specific photo set can be addressed, rather than attempting to sort through hundreds of photos. My general approach to taking photos for each set is to make sure that each photo is overlapping, and that they are all taken close enough to the object that small details are apparent. This not only improves the texture produced for the final model, but also aids in photo alignment in the case of uniformly colored surfaces.
There are a large number of free and low cost software options for working with 3D capture and digital heritage development. My current software toolkit includes Agisoft Metashape, Blender, and Unity. Agisoft Metashape is photogrammetry software, and has an educational license available for students and faculty of accredited institutions. Blender is a free 3D modeling tool which can be used for retopologizing photogrammetric models after they’ve been built, and also for generating creative 3D assets. Unity is a software development kit which can be used to make applications that can be built to run on numerous platforms, and comes with pre-programmed assets that make it accessible to people with little to no programming experience. Although there are free tutorials online, I feel that it’s worth mentioning that everything that I know about Unity and Blender has either come from reading software documentation, or watching videos at CGCookie. CGCookie’s tutorials are not only extremely comprehensive, but explain techniques and best practices that are often omitted in other videos.
The ease of access to user friendly software development tools has revolutionized digital heritage content production. In the future I hope to produce a number of educational tools using augmented reality and photogrammetric models, with project ideas ranging from archaeological dig simulations, to applications that let you try to put broken artifacts back together. For those who are just getting started in 3D content creation, don’t get discouraged! Although I’ve created a countless number of models over the last four years, I learn new things regularly from trial and error. While I genuinely believe practice is the best learning tool for photogrammetry, user manuals, articles, and videos are important for building a basic understanding of the 3D capture process. The knowledge is out there, and you too can make 3D heritage content with a little bit of patience and perseverance.