www.kraytracing.com

Does Kray going to support Color Vertex Maps?
It is very usefull for rendering big amount of instanced trees.

We're using following workflow:
Bake ambient GI to vertex color map (trees have plenty of vertexes to make it look good enough). Now tree requires sunlight only, a rest of lights/GI can be excluded from calculation. It works well with HD Instance in LW.

So i suppose if you put KraySurfaceOptions shader to tree surfaces and set Diffuse model to stright Raytrace you will get fast and good looking instanced trees.

I don't know if Kray supports color vertex maps, but you can use the Kray surface shader to tell it to use only light map for GI. With frame blending or shared GI, you get really fast render times and good quality.