As we've covered before, blurring is generally a *raster* function, whereas the noise functions you're dealing with are - at least to begin with - procedural or "vector" in a sense, i.e. they have a non-fixed resolution. Blurring generally works by averaging samples over a number of adjacent pixels, which is just not possible when your source data is, er, not made up of finite pixels as in the case of procedural functions. I haven't seen any implementation of "procedural blur" though, like "procedural erosion", it may be possible.
What you *can* do is rasterize your procedural function(s), in the case of Terragen by using a Heightfield Generate shader and feeding in the output of your shader network. This rasterizes your shaders to a resolution set in the Generate node's settings. But it does it for displacement. You can then reconvert to non-displacement (color values) if that's what you want, probably by using "Shade by Height" in the heightfield's options. But as you are probably gathering it's a little convoluted. Anyway, after doing that, you could apply a Heightfield Smooth operator, which is a type of blur.
- Oshyan
