Well I got displacement working purty good in PoseRay. I started with a fairly hi poly rock and in poseray I selected an image map, applied it. Then under U/V
I selected Cubic and applied it. The texture needed scaling so I set it for 2 in both directions and applied. Then in Groups I selected Displacement, browsed to the image map, and set Amount of displacement to White = 0.05 , clicked on Use adaptive subdivision before displacement, left Threshold default but clicked Create gradient map and left subdivisions at 2. Then clicked Create gradient and then Displace geometry and I got the rock you see here.