Isometric Terrain Editor

Question

I am trying to make an isometric terrain editor. My problem is not to do with making isometric graphics or rendering them, rather it is to do with indexing of tiles.

Let's say I'm making a hill at tile(10,5). This would mean that tile(10,5) will be type corner_1, tile(11,5) will be corner_2, tile(10,6) will be corner_3, and tile(11,6) will be corner_4. This will create a peak in the middle of the four tiles.

It seems simple to start with, but there are so many possibilities. If we have two hills that cross over each other, we would need inverted corner tiles. If we had a diagonal mountain, the surrounding tiles would need to be turned into diagonal inverted corner tiles. I've already created most of the images for the tiles http://opengameart.org/content/simple-iso-city-work-in-progress. My question is, is there already a set of "rules" I can follow for how terrain modifies itself around surrounding terrain? Or do I have to figure out every combination of tiles myself?

Answer 1

If you have the height of each corner you can easily find which tile to use. For example on the following drawing, the tile number 1 has hills on its top corner and left corner. The tile number 2 has a hill on its left corner.

To know which tile to use you would write something like that :

if (top_corner_height == LOW
&&  bottom_corner_height == LOW
&&  left_corner_height == LOW
&&  right_corner_height == LOW)
{
    tile = FLAT_TILE;
}
else if (top_corner_height == HIGHT
&&  bottom_corner_height == LOW
&&  left_corner_height == LOW
&&  right_corner_height == LOW)
{
    tile = ...
}
else if (...)
{
    ...
}

You just test every case possible.