I think i know what you mean, sometimes i make what i would consider to be a insignificant change and vue decides to totally recalculate the terrain changing its shape completely. A few times this has happened when i have already placed trees and other objects on the terrain. Then the terrain shape is changed and everything must be repositioned and there is no way to get back the original terrain! Some things i know do set it off so i am able to work around them and make sure i do any adjustments before i know it will be a problem. Things to watch out for are changing the mapping type of the texture on the procedural terrain. Example if you change the texture from Object Parametric mapping to World Standard mapping it will effect the terrain. Also if you load a new texture that has a change of mapping type from what is currently on the terrain. Any changes to the terrain settings like changing the quality, or like i said before scaling it or rotating the terrain in the main editor will all make it recalculate. So when you know some of these things you can work around and change all these settings before you start placing other objects relative to the terrain. Best of luck, procedural terrains are so much more realistic and flexible in use that they are worth the painful issues. I have used them in nearly all my images and i don't think i would ever use standard mapped terrains again! Regards -Jeff