The Rigging Workshop

We've spent years chasing rigging diagrams with pencil and paper. These hand-crafted diagrams are satisfying to make, and we've gotten good at it, though it can be a little hard to tell which lines are which.

We also work with SVGs. The colours are nice for determining different attributes of hitch structure, and they're much more adaptable than hand drawings when something needs to be adjusted.

The process is rather laborious, though. A larger rig like this one from the rigging specification might take several days to produce, and even smaller ones for testing the theory can take a decent chunk of time to develop. Much longer than the hand drawings, or even a zoom whiteboard.

I'd experimented with making an SVG editor for rigs. I've made a lot of different SVG editors over the years — I think the first was a web-based modular synthesizer back around 2012, when the Web Audio API came out. It was fiddly, but fun.

Making rigs this way is somehow even more fiddly. A lot of the things you need to say about a rig aren't really visible in our usual representations. This holds especially true for test rigs, which often contain non-standard elements. Requirements and satisfactions, for instance, are subsumed within a “prev” line, and simply assumed to be correct should that line be present. To create a test rig where an implementation is exercised in a precise way requires breaking that link, and the visual indication has no way of showing exactly how it is broken.

We already have a visualizer for analyzing the structure of toda files.

What we needed was a language for describing the rigs we were creating. It needed to be high-level enough that humans can read it — and even more importantly, write it. It also needed to be low-level enough that it could describe many of the stranger variations we have created as part of the standard test suite of toda rigs.

So a few weeks ago my colleagues and I put together the TRDL format, and they've pushed forward on building tooling for creating .trdl files, compiling them to .toda files, and decompiling .toda files back out to .trdl. It's a specific structuring of JSONL, which makes it easy to append and extend.

Meanwhile I've made some progress on building a Rigging Workshop for using TRDL files to their full effect. It's come a long way from the early zoom design sessions. We've got some fiddling to do to get the plumbing all in place before opening it more broadly, but it's already making the testing process substantially easier, opening the door to the next generation of rigging structures. We're incorporating both browser-based and server-based checking, so we'll be able to see the results right alongside each other and iterate to finding a good set of test rigs for that which stretch future implementations in the right ways, to supplement the automatically generated test sets from the formal verification work.