Hi folks.. Thanks for the info!
Yeah, I've tried using the various tools mentioned, it just seems to be very difficult to "rein them in", so to speak. Adjusting the strength for the Smooth tool, for example, goes from doing almost nothing straight to overkill, with very little gradient in-between. It's difficult to get very "fine-tuned" control outside of using the "grab" tool, which is great for tweaking local areas (smoothing out jaggies, etc), but way too inefficient for larger areas.
I think the thing with T3D's terrain tools is that they don't function as I'd expect them to, compared to pretty much every other terrain editor I've used, including Commercial and Indie engines alike. For example, trying to smooth out an area tends to result in lowering it instead, without actually smoothing it. It becomes this kinda "smooth staircase" effect, instead of a smooth slope. Same goes for the flatten tool. In other editors, the flatten tool gets the height of your brush at the point you left-click, and then brings the terrain up to that point as you move it around. In T3D it seems to continuously keep checking for the height beneath the brush, and adjusting the terrain to it, so the height it's "flattening" to is always changing as you move it around. The effect is uneven terrain, instead of just flattened.
I know there's the "set height" tool, and that's helpful, except that there's a quirk in the editor where the paintbrush seems to "jump" to other locations on the terrain at random - without you even seeing it. So, I'll be spending time working on an area of terrain. Then, when I move around the terrain, there's holes or mounds scattered all over the place which then have to be fixed. And they're in spots I'd never even looked at, much less edited.
While I could reproduce a similar type of terrain, with similar accuracy in myriad other terrain editors, I just can't fathom how they got that kind of precise control in the T3D editor. That's partially why I asked how they accomplished it - in addition to being really impressed by it.
Maybe people have found some good tricks that provide a good balance of control and intuitiveness with the tools?