Now using the Magic Wand Tool, (making sure Sample Merged is Checked and the Threshold is 0) click anywhere in the dark area. This will define your coast. If you want to adjust it, just undo the selection (ctrl-Z) and change the levels of the “Land Clip” layer. I wand back and tightened the coast a bit.


Now Invert the selection (Select->Invert), create a new black layer called “Land Mask” and fill the selection with white. Now save the selection to a Channel (Select->Save to Channel) and rename the channel to “Land Mask”. This will be used a fit bit later.

Now clear the selection (Select->None).

That technique (the Three-Layer-Sandwich of noise, shape and threshold clip layer, or TLS for short ) will be a basic technique that will be used over and over again, using different blending modes between the noise layer (to give some variegation to the surface) and the shape definition layer. It will be used to define forests and mountains, even clouds in the sky.

This is a fantastic guide! I've gotten further on here than I ever have in map making. However, I'm stuck on post 4 (I appreciate this isn't exactly far in the process). I select, invert and save my channel calling it Land Mask. However, after that, I'm left with the pure white Land Mask and not my full screen like you do. I've followed what you've said to a tee many times and don't get where I'm going wrong. I'm obviously missing something somewhere!