I may be wrong about this, but I don't think you have to be that exact. AFAIK, as long as the Minimum Displacement bounds is greater than the maximum displacement you've used in any of your material shaders, then you should be OK. (I regularly use displacements varying from (eg) 0.1 -> 0.8 in different materials; then set the Min. Disp to 1.0 and it seems to work.) The only other thing to be careful about is where different surfaces meet .. and that can get tricky. Best bet is to ensure that there's NO displacement along the joins, especially if the surfaces are at angles to each other.. Cheers, Diolma