Ahhh, I think I understand now, and yes this would be due to the 3D nature of the fractals that drive your displacement. So you can either 1: use an image map (several of them perhaps, tiled at different sizes, to avoid repeating patterns) to drive fine detail displacement - this would avoid the variations in procedural noise lookup position. Or you *may* be able to find the right combination of values for Transforming your displacement noise function(s) such that they keep pace with the terrain displacement changes and remain static relative to them. I imagine it would be a bit difficult to do this, especially with ease-in/out in an animation, but if you have a known rate of motion it might be possible. Still the static texture mapped displacement might be easier to implement.
- Oshyan