I'm not sure how to explain this, but is it possible for Terragen to handle convolution matrixes? Usually pixel manipulation, but can also be multichannel vector convolution. There are some really neat effects you can create from a basic matrix pallet (0..1 value for each matrix value). Maybe Daniil would have a better idea if TG could. It would allow sharpening fractals, or blurring them, or creating interesting effects to use in texturing. Like wood grain based on a stretched smooth PF.