I like trees. Of course there are many ways of creating them (e.g. explained here) but the tree of Airborn got my special attention because when i saw it the first time, i thought:

“Wow, this looks soo fluffy!”

Source: Airborn

I asked in their polycount thread how it’s done and the solution is pretty “simple”. KatziImSack replied and here is the picture:

Source: Airborn

You could use an inverted light vector to lighten up the back faces but that would be too easy. :D

They modified the normals. This means they used the inner “bubble” object as a base and “projected” the normal orientation of it to the leaf “cloud”. So you don’t get too dark/bright faces in the wrong place but a very nice and soft shadow gradient all over the leafs.

Normal Transfer Script: SlideNormalThief @ Slide London

If you think i didn’t explain it good enough, feel free to read more about this in the polycount wiki. There you also find the mentioned script which makes the copy process possible. And of course this link, which is so awesome i have to post it here: It’s about the shading of gras.

Warby told me another very nice advantage about this technique: You avoid too many transparent planes being rendered over each other. The big blob mesh in the middle culls most of them so you only need to care about the stuff of the front/sides.

Update 1

Megan Varde was so inspired that she made these cool trees. <3 <3 <3

Update 2

Dave mentioned another great example for trees using a similar tech:

Update 3

Emory has created a TUTORIAL about how to adjust the Normals in Blender, to achieve similar results like the Airborn tree. Should this tutorial-link be dead or offline in the future for some reason, I stored it as a picture on my server.

Update 4

Just found this great tutorial (also available on Gumroad) by Romain Durand and had to post it here! :)

Normal Source: Romain Durand