I just recently stumbled upon an issue where my doodads weren't showing up on top of my texture, but it showed up just fine on another one.
After some experimentation I realized that no matter what, if your 3rd texture (maybe 4th too idk) is sitting on top of the chunk's 2nd texture, it does not spawn doodads.
Here as an example below:
The image shows mostly a 2x2 square of chunks. All 4 chunks have 3 textures on them, dirt, forestfloor, and grass. On the left side you can see the forest floor on top of the dirt, and the grass on top of the forest floor. On the right side, all 3 textures are present, however the forest floor texture is not touching the grass texture.
On the left side the doodads did not spawn because the grass is touching the forest floor, where as on the right side the doodads did spawn because the grass is not touching the forest floor.
By this experiment you can see that the 3rd texture will not spawn doodads on its chunk if it is touching the 2nd texture.
I don't know if it's just GroundEffectAdder, or if that's just how WoW's engine works. Either way, I felt it was important to share this before anyone made the mistake.
