Root group geometries, Lie algebras, and polar spaces

The shadow geometries of spherical buildings corresponding to root nodes have been characterized as point-line incidence systems in terms of what is called root filtration spaces. This characterization is useful in that abstract root groups as introduced by Timmesfeld and simple Lie algebras over a field char. at least 5 containing an extremal element are easily seen to lead to root filtrations spaces. I will survey these developments and focus on two questions of more recent research:

1. To what extent is the above Lie algebra structure determined by the root filtration space?
2. Is there a direct proof of the characterization as a root filtration space of the line Grassmannians of polar spaces?