Something to be aware of is that while Terragen and World Machine both use Procedural Functions to generate terrains, World Machine always *rasterizes* those functions to a finite resolution, which limits your detail, but has the advantage of being able to perform additional raster-only operations like blur, etc. Terragen keeps things entirely procedural (generated at render time) and thus the functions have near "infinite" detail, but you aren't able to do things like blur operations unless you manually rasterize your procedural function, at which point you lose many of the advantages of purely procedural terrain (but again you gain some capabilities, like ease of export, and being able to run blur, erosion, and other raster functions).
- Oshyan