> Second, I tried to set "tree_bot" & "tree_top" Z-Order depending on their Y position, from top to bottom, so that higher trees are hidden by lower ones.
I don't see a reason to split the tree in two objects. Can you not achieve what you want, with complete trees?
In this example that are two complete trees, where the tree behind is partly hidden.
It's because I want Link to appear if front of the bottom of the tree, and behind the top.
does this suits your needs?
<a href="https://dl.dropboxusercontent.com/u/23138239/link_daewa_scirraforum.capx" target="_blank" rel="noreferrer" style="cursor:help;display:inline !important;">https://dl.dropboxusercontent.com/u/23138239/link_daewa_scirraforum.capx</a>
Thank you, thought I wanted to avoid using arrays cause I didn't want the tree on a grid (so trees can appear like the image above, I know it doesn't make sense with me wanting to avoid overlapping but I wanted to try anyway), but I guess I can make it appear less "griddy"