Sylistic foliage shading in Cycles? Like The Witness

Question

I'm looking to create some pseudo-"flat shaded" foliage, for lack of a better term. Basically I want all the planes that make up the foliage to have the same lighting so they blend together more.

Here's what I've got so far (excuse the ugly):

The lighting of each plane is pretty different and therefore you can easily spot each plane, especially where they meet.

If you look at the bushes, in particular, on the bottom of this screencap from The Witness, you can hardly make out the individual planes.

Here's another pic from The Witness, I think this was from their dev blog, the foliage looks very cohesive and the shading is very even across the whole thing.

http://static.gosunoob.com/img/1/2016/01/the-witness-pink-tree-puzzle-5-1024x640.jpg

I have read in a few places that one thing to help get more even shading on foliage is to edit the vertex normals so they are more rounded out. I tried using the "Normal Edit" modifier with no success. A lot of the foliage gets much darker and some places look much worse.

I found 2 addons that are supposed to help perform this process, I couldn't notice any difference when trying to use either of them. They both seemed to be years old and I'm not sure if they work with Cycles or work with the latest versions of Blender at all.

Transfer Vertex Normals Addon

Recalc Vertex Normals Addon

Answer 1

I think what your aiming for is a fairly shadeless look which in cycles can be achieved with the Emission shader.

The color variation can be created by varying between two base colors via a Fresnel node, then adding some additional variation with a noise texture.

Here's an example of how this could look:

And a closer look at the node setup for easier reading: