Reflecting on the issue with Rack and Unreal vis-a-vis viral open source licensing, there is one primary hurdle to overcome. The reason why I’ve been using a modified version of Rack in the first place is that I needed access to the SVG filenames used for module graphics, and Rack as-is does not expose the filenames. It is a small but critical change. Without that information, I can’t pass the file off to Unreal to render, and then I don’t have any textures.

But maybe the assumptions I made at the beginning of this project, with much less experience working with Rack, are not necessarily correct.

I recently implemented module previews in the library in Unreal. This was made easier by the fact that Rack provides a command line flag to automatically generate PNG renders of each module. Presumably, this is in place as a utility that the Rack developers themselves use to generate previews for the VCV Library, because the previews in the library within Rack are rendered the same way the actual modules are—on the fly, from the SVG.

BUT HOLD ON. How did I overlook this? If rack itself knows how to render an SVG to a PNG, that means there must be an interim step where there is simply an array of pixel data. And of course there is, because I have fully rebuilt the Rack SVG rendering pipeline in Unreal to ensure that my textures look the same, and I have an array of pixel data I’m writing to a texture target in Unreal. So what if, instead, I follow the preview-generation example from Rack, and let Rack render my pixels?

And so, I spin up a new Rack module project to experiment with. I learn some things about how the OpenGL libraries work. Before long, I have the beginnings of a solution. Better than that that, I come to an incredible realization: If I’m letting Rack handle the rendering, in addition to rendering the SVG data, I can render the dynamically drawn graphics as well!

If you’ve been following along since the beginning (hi! who are you?), you’ll know that accessing the run-time graphics was something I was almost completely certain I would never be able to do. But now, behold, a render of the panel like I was handling myself before, and a render of just the panel’s run-time overlay graphics:

Holy shit. Can I really make this work? And better than before?