It should be fairly simple, given that you've already got the terrain in. As long as you're outputting the images in a format that TG2 can read, you can load them with either an Image Map Shader or a Default Shader.
What you'll want to do is setup the texture you want to control with the "selector" image. So for example create a Surface Layer, give it a color, some displacement, etc. Then go to the Blend Shader input near the bottom, click the +> button and go to Create New Shader, Colour Shader, Image Map Shader. Now find your image in the file dialog that pops up and select it. Next, you need to set the camera projection to PlanY at the top, and then set the size of the image to be the same size as your heightfield (Geocontrol should be able to tell you how big it is in meters). Once that's done, it should then be controlling the distribution of your surface layer as expected. Mind you it may also be under the influence of the Fractal Breakup input, which you can disable if you want to control it exclusively with the "selector" map using the Blend Shader, or just disable temporarily to see the full influence of the selector on the surface layer distribution.
Of course I didn't cover the Default Shader, and there are in fact other ways to do this as well. That's one of the things about TG2, there are often different ways to do things that may provide similar results. The underlying techniques that make several methods possible to achieve a single effect are usually available in order to achieve other effects not otherwise possible.
- Oshyan
