Cultural Heritage Imaging

New Work in RTI: A report from recent conferences and meetings by cdschroer
June 19, 2014, 9:13 pm
Filed under: Commentary, Conferences, Technology

I have had the good fortune to attend a few recent events that allowed me to see some really useful work other folks are doing in our field. I thought it worth a blog post to mention a few with some links.  I’ll note that I have seen even more cool stuff, but if there wasn’t a paper or a page I could link to, I decided not to include it here.

First, Mark Mudge and I were at Computer Applications and Quantitative Methods in Archaeology (CAA) in late April in Paris.  Yes, I know, it is a hard-knock life having to present your work in Paris in April. I always love CAA because it is a great conference for sharing information and real-life experiences.  People are super helpful, and everyone wants to see everyone else succeed.  This isn’t the norm for a lot of conferences.


Musee de Cluny, Paris

Musee de Cluny, Paris

I want to point out 2 projects from there.  The first is Eleni Kotoula’s RTI on Papyrus case study.  New here is Eleni’s use of multispectral imaging and also her experiment with transmitted RTI.  Eleni was interested in information for conservation about the state of this papyrus, which is mounted on cloth and under glass. The second project at CAA isn’t an RTI project, but it’s very cool and worth mentioning anyway.  It is the work of Adam Rabinowitz et al. on PeriodO.  As folks who follow our efforts know, we at CHI are big fans of metadata, process-history tracking, and related topics.  Figuring out how to talk about periods in archaeology and art is really hard, and Adam and team have an idea for an interesting approach.  This project recently won National Endowment for the Humanities support, so it will be able to go forward. You can and should contribute to this effort yourself!

Next up is the American Institute for Artistic and Historic Works (AIC) conference, which took place at the end of May, right here in San Francisco.  It was great for us to have so many folks we have worked with here in SF.  One of the things I noticed at this conference was that Reflectance Transformation Imaging (RTI) showed up in a number of talks, though that wasn’t the focus of the talk. RTI is another tool to look at objects people are studying, and RTIs are being shown right alongside IR images and X-rays and the like.  YAY!  My takeaway is that RTI is an accepted part of the practice for art conservators. We are super happy to see that.

Finally, I was able to attend a 3-day workshop on RTI current practice and future directions, hosted by the Cyprus Institute in Nicosia, Cyprus in early June.  This was “All RTI, All the Time!” and it was very productive to be part of a dedicated meeting like this. There were many noteworthy projects presented there, and I’ll point out a few.  Up first, the work of Todd Hanneken and others integrating spectral imaging and RTI.  While many of us have done spectral imaging and RTI going back several years, what is new here is the use of a MegaVision monochrome camera system, and taking 11 spectral bands. RTI was shot in the visible and used for luminance data to generate the RTIs, and the color data collected via the spectral bands was then applied to the images shot in visible light.  The team also tested shooting full RTIs in each spectral band for comparison. In addition, work from the Visual Computing Lab in Pisa for a WebGL-based RTI viewer, released in January of this year, was discussed.  At the moment, this work is limited to streaming large RTI files and then allowing the user to pan, zoom, and relight, but some possible future directions were outlined.  It is open source, so you can try it out yourself.  There is also a project at The University of Southampton to develop a web-based RTI viewer, and we received an update on that project, but I don’t have a link where I can send you just yet.

RTI group in the old city of Nicosia

RTI group in the old city of Nicosia

As part of the discussion on where RTI is going, there was a lot of interest in quantitative uses of RGB and normals data.  There are a variety of people working in this area, though they didn’t present directly at any of these meetings.  Several of these folks are working with us at CHI, and we are very excited by this direction.  First up, the work of Dale Kronkright, Greg Bearman, and several others to look at tracking changes through normals, and also to quantify normal calibration.  You can find both papers here.  Additionally, there is great work going on at Simon Fraser University under Professor Mark Drew to improve the accuracy of surface normals calculated from RTI data sets.  They are also working on improving the appearance of RTI data in the viewing environment.  There are a number of papers on this topic, most recently the masters thesis of Mingjing Zhang.

It is an exciting time to be working with RTI data!  There is much more work going on than I could include here, and more that hasn’t been published yet.  I want to close with a plug for the CHIForums where many topics like this are discussed, and there is a Projects Forum where folks can put up links to their work, as well as get comments and feedback.