Got sidetracked into this cave, and encountered some problems. Tg can't handle the vector displacement perfectly, as in some POV's some 'triangles' were not rendered (though they were visible in the preview), so sky shone through. Increasing the displacement tolerance doesn't help. By carefully choosing the POV it can work out ok, proof attached.
Another problem is populating stuff inside the cave. You can copy location and set the pop there, but it took quite some effort to get them really inside the cave, and not on top of the mountain above. E.g. I had to set the location at the entrance of the cave and use a large pop size to cover the inside. If I'd pick a location near the camera, and even with a height restriction, objects didn't pop inside the cave. If I pop just outside the cave, and restrict by SSS to inner area, no instances appear.
