OK enough of the pretty coloured squares. "What's the point?" you may ask. The example in the first post shows multiple "binary" masks using a single mask image. This in itself is pretty cool. Now let's take the lakes as an example. In my render they are all the same colour. In all satellite images, there are two large lakes in the centre of the south island that show up as being much lighter (shallower). In higher resolution imagery, you can also see some subsurface detail in many lakes giving you a sense of the depth of the water.
Starting with the satellite image and a slope map I first created a mask for the boundaries of the lakes. Using this mask as a selection, I copied the RGB image of the lakes to a new layer in Photoshop, extracted the blue channel, normalised it's pixel values and then set the black output level to 225 so that the lakes' pixel values ranged from 225-255. The rest of the image was filled with black, but would normally contain the other masks.
Now into TG2.
Load the image and use a colour adjust shader to set the black and white levels to 0.8, and feed this into the fractal breakup of a surface layer, creating the boundary of the lakes.
Link the image to a second colour adjust node, this time setting just the black level to 0.8, giving you a full greyscale image of the greyscale values from the RGB image. While you might expect stretching 30 pixels values out to a 255 pixel value range would contain significant banding, you have to remember than anti-aliasing was applied prior to the colour adjust, smoothing the pixel boundaries with intermediate tones. The result is instead incredibly smooth.
Apply this to the fractal breakup of a surface layer to act as a blending shader between a light and dark water colour, tweaking the gamma in the colour adjust node to get the desired effect. The end result is a hack of inland water bathymetry. There is an edge effect in the render below, and I need to invert the mask greyscale values to reverse the effect so that the edges appear as shallow water. The edge effect will still be there, but it will be cunningly disguised
I'm always impressed by just how flexible the colour adjustments are in TG2. Given that I've started with an 8 bit image and applied some pretty severe adjsutments to a very small tonal range, the results are *very* smooth. This "feature" helps to make this technique more flexible by allowing more tonal masks to be squeezed in to a single image.