Add documentation to InputGroups and fix input recreation

Author: carson-katri

api/tree.py

@@ -29,7 +29,7 @@ def build_tree(builder):
         # Clear the node group before building
         for node in node_group.nodes:
             node_group.nodes.remove(node)
-        while len(node_group.inputs) > len(signature.parameters):
+        while len(node_group.inputs) > sum(map(lambda p: len(p.annotation.__annotations__) if issubclass(p.annotation, InputGroup) else 1, list(signature.parameters.values()))):
             node_group.inputs.remove(node_group.inputs[-1])
         for group_output in node_group.outputs:
             node_group.outputs.remove(group_output)

book/src/SUMMARY.md

@@ -18,6 +18,7 @@
 - [Advanced Scripting](./api/advanced-scripting.md)
     - [Node Groups](./api/advanced-scripting/node-groups.md)
     - [Generators](./api/advanced-scripting/generators.md)
+    - [Input Groups](./api/advanced-scripting/input-groups.md)
 
 # Tutorials
 

book/src/api/advanced-scripting/input-groups.md

@@ -0,0 +1,75 @@
+# Input Groups
+
+Some geometry node trees need a lot of arguments.
+
+```python
+@tree("Terrain Generator")
+def terrain_generator(
+    width: Float
+    height: Float
+    resolution: Int
+    scale: Float
+    w: Float
+):
+    ...
+```
+
+There are a couple of problems with this. Firstly, the function signature is getting long. This can make it harder to visually parse the script. And, if we want to use the same arguments in another tree and pass them through to `terrain`, we need to make sure to keep everything up to date.
+
+This is where input groups come in. An input group is class that contains properties annotated with valid socket types.
+
+To create an input group, declare a new class that derives from `InputGroup`.
+
+```python
+class TerrainInputs(InputGroup):
+    width: Float
+    height: Float
+    resolution: Int
+    scale: Float
+    w: Float
+```
+
+Then annotate an argument in your tree function with this class.
+
+```python
+@tree("Terrain Generator")
+def terrain_generator(
+    inputs: TerrainInputs
+):
+    ...
+```
+
+This will create a node tree with the exact same structure as the original implementation. The inputs can be accessed with dot notation.
+
+```python
+size = combine_xyz(x=input.width, y=input.height)
+```
+
+And now passing the inputs through from another function is much simpler.
+
+```python
+def point_terrain(
+    terrain_inputs: TerrainInputs,
+    radius: Float
+):
+    return terrain_generator(
+        inputs=terrain_inputs
+    ).mesh_to_points(radius=radius)
+```
+
+## Instantiating Input Groups
+
+If you nest calls to tree functions, you can instantiate the `InputGroup` subclass to pass the correct inputs.
+
+```python
+def point_terrain():
+    return terrain_generator(
+        inputs=TerrainInputs(
+            width=5,
+            height=5,
+            resolution=10,
+            scale=1,
+            w=0
+        )
+    ).mesh_to_points()
+```