Tile generation/placement

Howdy, I''ve completed my first project, which is a 3d terrain renderer based on a height-map. This isn''t strictly speaking isometric, but I am using tiled textures. The algorythm I am using to get the blend pieces correctly selected as you paint (so that there is a smooth transition from one terrain type to another such as between grass and mud) is pretty simple and goes pretty much like this: 1: For each blend tile, I create a 3x3 join map that determines which edges of a quad the blend tile fits against. 2: As I paint, I iterate through each of the 8 tiles surrounding the one I am working on and generate a join map for the region. I then go through each of the join maps for the blend tiles to find the tile that fits the desired join map. This works pretty well most of the time, although it can cause problems because of concurrency (i.e. if I generate the regional desired join map by scanning left to right, top to bottom, a change in the middle part of the join map may require a change to a tile in the first row, but because the first row has already been computed, I can get a glitch). I am purely curious to know if there is a better way to do this? My method works fine, but it does require a bit of care when creating to blend tiles because I have to create a join map to go with it. Learning to fly is easy, but as a tortoise, the landings are really rough.