Can I ask you to explain vertex light shadows and shading more? I've been working on my own personal projects studying vertex shading in my free time in the effort to understand how it was done on old school titles such as on the ps1. But I'm not familiar with anything casting light so dynamically like what was done in your video?
Late reply soz.
I'm not aware of anything that actually uses this kind of shadows, especially because what I did relies on normal shadowmasking stuff, and since the scene has to be render for every shadow-casting light to get the shadow mask, I'm not sure you gain that much by sampling the shadowmask texture only in the vertex shader. Might be an interesting thing to explore anyway? In my case it does get sampled in a worldspace neighborhood per-vertex and then averaged, which might be a cheapish? way to get soft shadows, but heh.
For vertex lighting in general, I've been simply looking up lighting models that are generally used and only applying them at vertices, nothing fancy there. For the latest bug-post and castle vertex shadow test scene, the actual lighting part was just bog standard Blinn-Phong.