it was called as terrain sewer, and you should search AUMs for it. I have it somewhere saved. but it is very simple, just set neighbouring terrains neighbouring vertices z value to their average by ent_getvertex/ent_setvertex. imo using more terrains is what you need, far away terrains can be clipped for better performance. only pro edition features terrain lod, but it is not perfect. but it will be very difficult to realize a level that looks great from close view near ground, and from high altitude, beside good performance. a while ago I saw a post about streaming entities, but don't know whether ti works or not... it would be great to have this feature. imo it is not too powerful to use huge view distances and huge worlds in gamestudio, but maybe someone else has more experience than I have in this area...