I use Octane but this also fails with simple mental ray... So, I think this is the best place to seek help...
I have a simple plane, and I want to add a material with displacement (Octane 2.0) to make it look like hills... Of course, nothing shows in the viewport... it is still a simple plane... Now I add a Forest object... Hit "Render" but the forest doesn't follow the displaced plane... I have tested with simple 2d plane forest object and then from the library... Is there a way to do this? I send you some images...