Generating new trees
If the built-in library of trees isn't enough, or you have a very specific tree model that you want as an Alpha Tree, you can convert almost any tree 3D model easily.
As the tree has to be rendered multiple times to create all the maps needed to turn it into an Alpha Tree, converting a tree can take anywhere from a couple of minutes to 20 seconds, it all depends on hardware, samples and resolution.
Before starting, you need to make sure of a few things:
The tree is a single static mesh, and has no particles (made by particle systems or geometry nodes) or instances on it.
The origin point of the tree is at the base of the trunk.
The tree has separate materials for the trunk and the leaves (This is to allow the addon to know what to separate into different layers).
To start, pick the tree object with the object picker.
Then open the material types panel. These are used to determine what part of the tree should go on which layer, for example, the trunk and branches type are put on the trunk layer, and the leaves, flowers etc are put on the leaves layer.
By default, these types are autofilled, but if the addon isn't sure about some of them, they will be highlighted red until you confirm or change them. (You can use the Autofill button shaped like an "A" to do this manually.)
Then you can check the settings:
Border padding: The amount of space left around a tree in the final image. Useful if the tree is not symmetrical, and part of it is cut off on the sides. Generally best at the default value.
Resolution: This is the final resolution of the tree. 1024 is good for almost all trees, but for very high quality (used for more close trees) 2048 is probably best.
Samples: The number of samples used for rendering. This should really never go above 50 and 15 is good for 99% of trees.
Library path: The library that the trees will be saved to. The same as the library path in the preferences.
Finally, you can hit the bake button. This will open a confirmation dialogue, but if you've followed to this point, you can ignore it. While the tree is rendering, the UI will be frozen, but if you want to see the progress, you can either open the terminal, or press the folder icon before you bake, which will open the library folder so that you can see the maps as they are added.
Once it's done, you can refresh the library to see the tree in the tree list, and add it to your scene! The final baked maps should look like this in the file browser.