Guitta, ok I will try this and report back when I have. How do I change the "peak" thing? The bitmap is also enormous. Maybe this is a problem? Kutter, hi! Yes, it was your tute (very good one by the way). It actually worked fine for the tutorial. Of course, that is a massive path right through middle of a terrain. Perhaps part of the problem is that my "rivulets" only occupy down at one small corner of a large terrain? What baffles me completely is why the material for the lava is appearing all over the landscape. I'm just not aware of having done anything fundamentally wrong (not that this means I haven't LOL) P