If you run rendering (Terragen) as a hobby, you don't have two or three computers at your disposal to work "adequately" (at least not me). So it would be desirable if you could work more smoothly with Terragen. So that you could implement spontaneous ideas and changes immediately without running the risk to crash Terragen. It would just be nice if Terragen would give you a hint with an error message after the crash what went wrong. Or that in case of a crash Terragen would be able to save the last state, so that after a restart you could continue working exactly where you were before the crash. I could also imagine running the rendering itself as a separate process: If you pressed "Render", this process runs independently from the rest of Terragen, where you can continue working. If there are changes that can affect the rendering itself, you would get a hint or something like that.