Creates a function node, which calculates normals for polygons.
It expects a list l of POLYGON3 or POLYGON3T nodes as its parameter. It creates a copy of this list, and replaces all POLYGON3 or POLYGON3T nodes in the copy with POLYGON3N or POLYGON3TN nodes.
When the function is executed (this happens for example when the function node is validated the first time after parsing an input file, or when there are changes in its parameter list at run time) the result node is created (or updated) and connected to the function node as its second node, so that the result can be accessed via the node selection operator [..] (or equivalently [2, ..]).
l is a typeless node to which the POLYGON3 or POLYGON3T nodes are connected.
The following variations of this keyword exist (some of them define the same internal structures, and are only defined to allow consistent naming conventions):