Artik: There are 20 texture types now (for each texture set). 16 small ones, i.e. 0 through 15, which get multiplied by 16 to create the Red channel, and 4 larger textures, 0 - 3, (mostly farmland for Europe texture set) which get multiplied by 64 to make the Green channel, and then the blue channel is 0 to select the small texture or 255 to select the large one. In my program I label these 0 - 19* and map them to the GlobCover indexes as shown in the attached file. For some I used secondary criteria: for example I map GC "bare" to sand if the alt is below 1500 m or to rock if it is above. This prevents sandy areas in the Alps. (In no way do I claim my mapping is in anyway good, but I attached it just as an example of one mapping for the default European summer texture set.) Obviously, if one is making their own texture set then they would design it to match GlobCover better. My program then exports to a 32bit bitmap and that seems to work fine with AH3.
The default texture sets are designed so that increasing texture index is used for increasing altitude (i.e. sand is 0 while snow is 15). When two textures are next to each other and are not consecutive, say texture 4 next to texture 9, then AH3 rendering engine ramps through all the intermediate textures in the area between them, ie 4, 5, 6, 7, 8, 9. So when you use GlobCover to make texture choices it's possible, in fact likely, that adjacent textures will differ by more than one in the texture index order and that leads to some visible banding (like the example image I posted earlier). I've started doing some analysis of the GlobCover texture connectivity stats to see if I can reduce the banding by just rearranging the order of AH3 default textures (which would require making a custom texture set).
*i.e. 0-15 are the small textures and 16-19 the four large ones (only useful for understanding the attached file).
