Been AWOL for quite a while ... now I'm enjoying the new TG4. I love how fast the preview is!
I know it's been mentioned that TG isn't really designed for controlled placement of specific terrain elements (mountain range here, valley there, etc.), but I think I'm close to achieving a methodology that works. I started by eroding a simple grayscale heightfield image in World Machine, then exporting the result to a 16-bit image so I could tweak a few areas in Photoshop to get more precise control. Problem is, importing the image via heightfield load creates stairstepping in smoother parts of the terrain, due to the notorious "banding" effect of minuscule gradients. (See attachment -- I turned off fractal detail to emphasize the effect.) Changing the interpolation method from "Catmull-rom" to "Over smooth" doesn't really correct it, and besides, it takes away important detail from the mountains. Part of my problem, I think, is that I'm using a heightfield multiplier to achieve the proper elevation for the mountains, which of course magnifies the stairstepping effect.
I'm hoping to create a nice, gentle slope up the valley, perhaps by using an image map mask created in Photoshop. Unfortunately the heightfield smooth and erosion operators don't have a masking option. I'm sure there's a fairly simple way to do this via shaders, but the proper combination escapes me. The concepts behind them have always been tough for me to grasp.
Any help is appreciated -- including links to any tutorials I might have missed! Thanks.