Ambient occlusion using blendable material in Post Process

Using Ambient Occlusion in post process is quite expensive on bigger scene.
Thats why I’m looking for a way to implement some sort of ambient occlusion using post process materials with array elements.
So far the results are ok but not quite good how I’d like them to be. Here is my material so far:

Right now the whole scene seems to get occluded, less so where there is light, but what I want to achieve is the effect where meshes overlap (like ground and a mountain) to have nice occlusion.