Creating a New Geometry / Function Node

tags: Blender

In addition to a file that defines the function of a node, there are several files that need to be updated to reference that new code as well. This document will create a new geometry node called Stub. The instructions will also reference changes to the stub code for creating a function node.

source/blender/blenkernel/BKE_node.h

BKE_node contains a mapping of a static number to a human readable name that will refernce the node. A search of GEO_NODE_ or FN_NODE_ (depending on the type of node) in this file will reveal a list of #define statements. At the bottom of this list choose an unused incremented number and assign it a name.

#define GEO_NODE_STUB 1111

Your Node Source Code File

This file will contain the logic and layout information for your node. This file will live in the folder appropriate to its type:

• source/blender/nodes/geometry/nodes
• source/blender/nodes/function/nodes

For the purposes of this documentation, we will create a geometry node stub called

source/blender/nodes/geometry/nodes/node_geo_stub.cc

The contents of this file will vary based on whether we are coding a geometry node or a function node. The main similarity will be a node registration function that the other files will reference. The layout of the main node file will be covered in another document.

void register_node_type_geo_stub()
{
  static bNodeType ntype;
  geo_node_type_base(&ntype, GEO_NODE_STUB, "Geometry Stub Example", NODE_CLASS_GEOMETRY, 0);
  
  // OTHER Node definitions and function references here
  
  nodeRegisterType(&ntype);
}

There are a few items to note in this code.

1. The name of the registration function is laid out as follows:

• register_
• node_type_geo_ // or node_type_fn_
• stub // name of node

2. Declare a bNodeType variable.

3. The geo_node_type_base() function takes the following parameters:

• The bNodeType variable that was just declared
• The define name from BKE_node.h is used as the 2nd parameter of the function.
• A display name for the node
• A node class (this determines what color the node header is among other things)
• 0. //TODO - leave 0

4. Register the bNodeType variable

source/blender/blenkernel/intern/node.cc

There is a function called registerGeometryNodes() in which to call the registration function defined in the node source file.

register_node_type_geo_stub()

source/blender/nodes/CMakeLists.txt

In the CMakeLists file go to the secion of files in the geometry/nodes/ folder and add the node source file in alphabetical order:

geometry/nodes/node_geo_stub.cc

source/blender/nodes/NOD_geometry.h or
source/blender/nodes/NOD_funcation.h

In the file corresponding to the type of node being created, add the function prototype of the node registration function in aplhabetical order:

void register_node_type_geo_stub(void);

source/blender/nodes/NOD_static_types.h

This file contains the node definitions. In alphabetical order add the DefNode line for the new node

DefNode(GeometryNode, GEO_NODE_STUB, 0, "STUB", Stub, "Stub Node", "")

The parameters are as follows:

1. Node Type: GeometryNode or FunctionNode
2. Define Name for the Node
3. An RNA function if the node requires it, set to 0 if this node does not have custom storage
4. Used for Python. Follow the define name minus GEO_NODE
5. Pascal case version of node name used for Python API
6. The menu entry name
7. // TODO (leave blank)

release/scripts/startup/nodeitems_builtins.py

This file contains the definition for the Add Nodes Menu.
Search for the appropriate GeometryNodeCategory to add an entry. The NodeItem name is a combination of the NodeType from the DefNode entry and the Pascal case version of the name.

NodeItem("GeometryNodeStub"),