Nodes are what a Generator makes as part of procedural modeling. Every single individual piece of geometry in the tree is a single node.
For example, a Branch Generator can make many branches on the tree. Each branch is a single node.
Similarly to how you can edit Properties on a generator, you can also edit properties on a node. 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 afterwards in exactly the way that they want.
Moving branches around, removing leaves in certain spots, adjusting the segments on a branch, and even overriding materials are different types of node edits you can perform on a tree.
The distinction between editing 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 Node Edit Mode, when you click in the Tree Window to select something, you will be selecting that individual node. The Property Bar will show the properties for that node, not the generator.
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.
When a node is selected and the Art Director is shown, you will be presented with a special node editing gizmo that lets you intuitively control major aspects of the thing selected.
If you hover the mouse over the various controls, you will be presented with a tooltip of what they do. Branches have controls for position, start angle, radius, length, etc. Leaves can edit position, rotation, and various deformations.
Deleting a node is as easy as selecting it and hitting the DEL or BACKSPACE key on the keyboard. Nodes that are deleted will remain gone even when values on the generator are changed.
Other Property edits on the node are offsets to the value the generator calculates. For this reason, when you select a node for the first time, you will see that all the property values are zero.
If you change a property, this offset will be added to whatever value the generator calculates before ultimately creating the geometry. 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.
Curve offsets work similarly for the few properties that show a Profile Curve in Node Edit Mode. This curve is added to the generator's before the geometry is calculated.
You can clear all of the node edits for a particular generator by choosing the “Clear Node Edits” option in the menu when you right click a generator in the Generation Editor. This will also bring back any nodes that were deleted.
Note: Randomizing parts or all of a tree will wipe out any relevant node edits, as well.