| siDefaultPort |
[0] The port is a regular port and must be connected. |
| siOptionalInputPort |
[16] The port is optional as does not need to be connected. |
| siCreatedOutputPort |
[256] The object connected to the output port is created when the operator is connected (not implemented for custom operators). |
| siBranchGroupPort |
[1024] The port can be connected to a group of a hierarchy of objects. |