I don't know if it's been mentioned already, but I think you really need to look into how to shade cylindrical or round objects.
You mean i haven't been frank enough in how dark the tree gets on the edges, i guess ... i'll try to fix that.
Or is e.g. the big branch of the hollow tree flawed too ?
(*edit*) i re-did the trunk focussing on volume only, in a rush, with coarse tools.
Is that proper interpretation of cylindrical shading to your eyes, or am i really to dig for tutorials?
Also, leaves! Think of these clusters as a pile of disks. Make them more fragmented. Look at some reference if you're not sure of how to place them or shade them.
Hope that helps!
Given how great it looks, i hope it'll help. I initially did studied the "minish cap" style of leaves, which i unfortunately wasn't able to reuse. I came with the current buch of very small and dense leaves as a refined version of those clumsy bunch of leaves with "polka dots" seen in the background of the scene.
those you suggest are brilliant, although maybe a bit too "unstructured" to my tastes (e.g. if i manage to do something that approach that level of awesomeness, i'd love to make the player believe that the orientation of leaves comes naturally from an invisible network of branches, too)
how do you proceed to get something alike ? start with gross BG shape in dark and then add leaves layer after layer, casting shadow on the previous ones as you add new ones ?
Anyway, thanks for your edit and comments. If i manage to apply that, i'll have learned lots i guess