References

Signed Distance Fields

Rendering Worlds with Two Triangles by Iñigo Quilez
Rendering a Screen Covering Triangle in OpenGL (with no buffers) by Randall Roel Rauwendall
Fast Approximations of Lights for Dynamic Scenes by Alex Evans is a pretty amazing tour de force and pretty much the first thing I ever saw that smashed together lots of SDFs into grids.

Shadow Mapping for Hemispherical and Omnidirectional Light Sources by Brabec, Annen, and Seidel covers (dual) parabolic shadow mapping, which would let us get away with a single shadow map per hemisphere, especially if we didn't have any of those pesky triangles. Hrmm. =)

The Future of Screenspace Reflections by Bartlomiej Wronski talks about some of the issues with using screen space approaches for reflections. However, it is interesting that at least in screenspace the reflections can reflect specular highlights.

Fast, Effective BVH Updates for Animated Scenes by Kopta et al. covers one interesting way to optimize a static BVH via the surface area heuristic through incremental swaps.
On the other hand the approach in Clustered Deferred and Forward Shading by Ola Olsson et al. approach of just sorting things in Morton order and gathering 32-way trees out of consecutive entries makes a much flatter structure.
We could apply an incremental approximate sorting algorithm such as the one advocated by Smash (Matt Swoboda) in his article on a thoroughly modern particle system. In theory tagging the entries in the map with a dirty bit / card marking when they swap places / move would be enough to avoid touching everything all the time as you only have to propagate dirty bounds up the tree.