There are two primary methods for editing a tree's anatomy: Generators and Nodes. Understanding the distinction between these will help you edit a tree quickly and efficiently.
Generators are shown in the Generation Editor. This is where you set up the major hierarchy of your tree. Leaves grow off branches that grow off the trunk, for example. When you select a generator, its properties are shown in the Property Bar. Edit one of these properties, and you are modifying all of the individual pieces of the tree that this Generator makes, all at once.
See the Generators section for more information.
Editing nodes directly allows you to adjust individual parts of a tree, to fine-tune what the procedural generation accomplished. This makes SpeedTree very “art-directable,” since an artist is able to leverage procedural generation to get close to what they want very quickly, but still be able to modify the tree afterward in exactly the way that they want.
Property edits to Nodes are offsets to the value created by the Generator. Because of this, you can edit a Node but still be able to edit a Generator. For example, you wish one branch to be longer, so you edit the length property of that one branch node. But then you decide you want all the branches to be longer, so you edit the Generator similarly. The one branch you edited keeps its offset and stays longer.
Note: Randomizing parts or all of a tree will wipe out any relevant Node edits.
See the Nodes section for more information.
The distinction between Generators and Nodes is so important that there are two different editing modes in the Modeler for them. You switch between Generator Mode and Node Mode using the appropriate buttons in the Tree Window.
Note: You can also hit the “Tab” key to switch between Generator and Node mode.
In Generator Mode, when you select something in the Tree Window, you are selecting the Generator. In Node mode, you will be selecting an individual Node in the tree instead. This is apparent with how the selected objects are shown in the tree (see below). When you select a Generator in the Generation Editor, you will always be put back into Generator Mode.