I started working on applying basic materials to the new .glb 3D objects today, and right away I realized that without a skybox/irradiance map for environmental lighting I couldn't proceed -- everything looks wrong without that. So I went ahead and hacked together a super horrible implementation for that, which needs a lot of cleanup but works.

With the skybox and environmental lighting set up, I went through and applied the same super basic textures to all the objects that I had used before, and also did some super basic material tweaking for parameters like metallicity, specularity, etc. My models and textures are still crap, but at least things look kind of right again. Here's an example of masses and springs, which look far, far cooler with a skybox.

The skybox is low res, the textures suck, etc, but even still, things look a lot better. I'm not sure what I will use for the factory-provided skybox; the clouds are nice but they imply a certain aesthetic that I'm not sure about. But it's getting me excited that if I have a real 3D artist redo the models that it might look really good.

There are still some things I need to figure out with Google Filament's materials. In particular I still don't have a way to highlight the selected objects. I think that I have to compile a custom Filament material, and am hoping that it's super simple to do that. I think it might be.