currently i'm using the voxelization method from gpu pro 3 and the cone tracing from http://www.geeks3d.com/20121214/voxel-cone-tracing-global-illumination-in-opengl-4-3/ with a R32UI 256^3 3d texture.
my render loop looks like this:
clear voxels
voxelize scene
create mipmaps http://pastebin.com/ubKVuzBW
render scene http://pastebin.com/xmBp8n2u
the result looks like this (indirect diffuse only):
my main issue is the blockiness.
i tried a 3x3x filter during mipmap generation, but that didn't help really.
also tried more texture fetches during cone tracing.
atm i'm out of ideas.