How can I take an image and create a flat 3D model out of it? So basically I have this game that I've been developing for a while, and it's been making use of heavy alpha cutout in Unity. I've been told over the course of the development about tile based gpu architecture, and that I will keep having a very hard time optimizing for mobile if I continue with having forests upon forests in where I can't take advantage of a mobile gpus optimization techniques. 

Here's what my game ends up looking like in Unity: 

https://media.indiedb.com/images/presskit/1/1/776/general/14_LeafProjAttack.gif

The trees look great with the alpha I think...but the problem with optimization has been really holding me back here...

I'm honestly wondering if there's a way in where I could create that same high quality look but just convert my 2d images somehow to 3d models? 

The good news is, since it's all pixel art, the edges are semi-predictable I suppose? Here's a sample image that I'd like to convert to a flat 3D model:

https://i.imgur.com/JnBKBiE.png

Is there a way to do this or am I going to have a very hard time per image that I convert to 3d?

Thanks for any help ahead of time that you can provide!
It's absolutely possible, look up billboard sprites. For generating them in Blender, get a render with transparency enabled (more googling) of one tree and then you can duplicate it around to fake a forest. It's also potentially a good idea to render some far off trees to make a distant background rather than rendering potentially hundreds of those billboard sprites.  It might be fun to experiment with more roomy tree renderings given you don't have to have unity do that part anymore...

Edit: totally opposite approach is what's being asked for here!

Instead, you can also start from the geometry which was alpha masked, and subdivide it (use simple instead of catmul-clark) then select verts that are outside the texture map and delete them. Probably don't want to subdivide too far before doing this because deleting verts can get boring...