AzureDVBB · July 17, 2018 21:22 · Jul 17, 2018
diff --git a/node_trees.py b/node_trees.py
@@ -0,0 +1,184 @@
+# the little less documented way of adding a custom node tree
+#   and populate it with nodes of varying types of I/O
+#   sockets that work together, discombobulated
+
+# first we import the blender API
+import bpy
+
+
+# then we create the UI space, the node tree as it is called
+#   but in actualy fact this is similar to a UI panel/menu
+#   and mostly handled in the background in terms of creation
+# so let's define out custom node tree, inheriting from its base type
+class CustomNodeTree(bpy.types.NodeTree):
+    # the docstring here is used to generate documentation but
+    #   also used to display a description to the user
+    '''A custom node tree type'''
+    # then we can give it a custom id to access it, if not given
+    #   it will use the classname by default
+    bl_idname='CustomNodeTree'
+    # the label is the name that will be displayed to the user
+    bl_label='Custom Node Tree'
+    # the icon that will be displayed in the UI
+    # NOTE: check the blender dev plugins to see icons in text editor
+    bl_icon='BLENDER'
+
+
+# that is all we needed to make a nodetree
+# first for convenience we make a class from which all our nodes
+#   will inherit from, saving us some typing
+class CustomNode(bpy.types.Node):
+    # this line makes the node visible only to the 'CustomNodeTree'
+    #   node tree, essentially checking context
+    @classmethod
+    def poll(cls, ntree):
+        return ntree.bl_idname == 'CustomNodeTree'
+
+
+# now we start making a simple input node that uses builtin
+#   blender properties, this is the simplest node
+# we define the node class that inherits from its mixin class
+class CustomSimpleInputNode(CustomNode):
+    # we can add a docstring that will be interpreted as description
+    '''A simple input node'''
+    # optionally we define an id that we can reference the node by
+    bl_idname = 'CustomSimpleInputNode'
+    # we add a label that the node will show the user as its name
+    bl_label = 'Simple Input Node'
+    # we can also add an icon to it
+    bl_icon = 'PLUS'
+
+    # we can add properties here that the node uses locally
+    # NOTE: does not get drawn automatically
+    intProp = bpy.props.IntProperty()
+
+    # init function that is automagickally is called when the
+    #   node is instantiated into the treem setup sockets here
+    #   for both inputs and outputs
+    def init(self, context):
+        # makes a new output socket of type 'NodeSocketInt' with the
+        #   label 'output' on it
+        # NOTE: no elements will be drawn for output sockets
+        self.outputs.new('NodeSocketInt', "output")
+
+    # copy function is ran to initialize a copied node from
+    #   an existing one
+    def copy(self, node):
+        print("copied node", node)
+
+    # free function is called when an existing node is deleted
+    def free(self):
+        print("Node removed", self)
+
+    # draw method for drawing node UI just like any other
+    # NOTE: input sockets are drawn by their respective methods
+    #   but output ones DO NOT for some reason, do it manually
+    #   and connect the drawn value to the output socket
+    def draw_buttons(self, context, layout):
+        # create a slider for int values
+        layout.prop(self, 'intProp')
+
+    # this method lets you design how the node properties
+    #   are drawn on the side panel (to the right)
+    #   if it is not defined, draw_buttons will be used instead
+    #def draw_buttons_ext(self, context, layout):
+
+    #OPTIONAL
+    #we can use this function to dynamically define the label of
+    #   the node, however defining the bl_label explicitly overrides it
+    #def draw_label(self):
+    #   return "this label is shown"
+
+
+# now to be able to see the nodes in the add node menu AND see it on the
+#   tool shelf (left panel) we need to define node categories and then
+#   register them, the rest is handled automagickally by blender
+# so first we import the utilities used for handling node categories
+import nodeitems_utils
+
+# now we can make our own category using the NodeCategory baseclass
+#   as before we first make a mixin class to save space
+class CustomNodeCategory(nodeitems_utils.NodeCategory):
+    # define the classmethod that tells blender which node tree
+    #   the categories made with this class belong to (is visible to)
+    @classmethod
+    def poll(cls, context):
+        return context.space_data.tree_type == 'CustomNodeTree'
+
+
+# make a list of node categories for registration
+node_categories = [
+    # NOTE: did not find documentation other then template script for it
+    # esentially:
+    #   we instantiate a new 'nodeitems_utils.NodeCategory' class, that
+    #   has been extended with a poll method that makes sure that the
+    #   category and node only shows up in the desired node tree
+    # The first argument is a string with its id we will use to access it by
+    # the second argument is the name displayed to the user
+    # the third argument is a list of (items) nodes that are under
+    #   that category, the list contains instances 'nodeitems_utils.NodeItem'
+    CustomNodeCategory("CUSTOMINPUTNODES", "Custom Input Nodes", items=[
+        # the nodes (items) in this category are instantiated in this list
+        #   with the 'nodeitems_utils.NodeItem' class, which can have
+        #   additional settings
+        # the first argument is the node class idname we want to add
+        # then there can be keyword arguments like label
+        # another argument can be a 'settings' keyword argument
+        #   that takes a dictionary that can override default values of all
+        #   properties
+        #   NOTE: use 'repr()' to convert the value to string IMPORTANT
+        nodeitems_utils.NodeItem("CustomSimpleInputNode",
+            label="Simple Input", settings={"intProp":repr(1.0)}),
+        # minimalistic node addition is like this
+        nodeitems_utils.NodeItem("CustomSimpleInputNode"),
+        ]),
+]
+
+
+
+#finally we register our classes so we can install as plugin
+#to that end we create a list of classes to be loaded and unloaded
+classes=(
+        CustomNodeTree,
+        CustomSimpleInputNode,
+    )
+
+# for loading we define the registering of all defined classes
+def register():
+    # we register all our classes into blender
+    for cls in classes:
+        bpy.utils.register_class(cls)
+    # we register the node categories with the node tree
+    # the first argument is a string that is the idname for this collection
+    #   of categories
+    # the second is the actual list of node categories to be registered under
+    #   this name
+    nodeitems_utils.register_node_categories("CUSTOM_NODES", node_categories)
+
+
+# for unloading we define the unregistering of all defined classes
+def unregister():
+    # we unregister our node categories first
+    nodeitems_utils.unregister_node_categories("CUSTOM_NODES")
+    # then we unregister all classes from the blender
+    for cls in classes:
+        bpy.utils.unregister_class(cls)
+
+
+# finally we make it runnable in the text editor for quick testing
+if __name__=='__main__':
+    # during test running there is a bug where registering or adding
+    #   references to certain groups and categories cannot override
+    #   existing ones, here is a workaround
+    # we enter a try..finally block
+    try:
+        # first try unregistering the existing category
+        # WARNING: ALWAYS triple check that you unload the correct
+        #   things in this block, as it will not raise errors
+        nodeitems_utils.unregister_node_categories("CUSTOM_NODES")
+    finally:
+        # finally, wether it suceeded or not, we can now register it again
+        #   this essentially reloads existing/register changes made
+        #   and thanks to the nature of the finally block, is always run    
+        register()
+