Or you can simply save the heightfield once you initially generate it by right-clicking the heightfield generate and choosing Save (make sure to specify .ter file extension), then replace the Heightfield Generate with a Heightfield Load and it should auto-load when you open the project. No need to regenerate. Of course if you want to change the heightfield settings later you must regenerate (and if you removed the Heightfield Generate, you will not be able to do so, of course, so don't delete it).
- Oshyan