Is the Signature parameter (e.g., in MtlX Multiply) documented anywhere? I was baffled by some of the choices. I did figure out what Vector3 (FA) meant.

The signature parameter switches the types of the node's inputs and outputs. It's a Houdini way of dealing with the same operation that has several variants, each differing only in the types it takes.

A MaterialX shader node can have several definitions that differ only in type it takes, and therefore such definitions fit well with Houdini's concept of a signature.

The signature name in Houdini comes form MaterialX name of the given definition (eg, "ND_multiply_vector2" and "ND_multiply_vector3FA"). We try to keep close to the original name, while making it a little bit more human-readable.

Thanks! Once I started looking around in the MaterialX library everything became clear.

Sorry for the necro, but what does (FA) mean? I noticed the noises have output type of Vector3 as well as Vector3(FA) which both seem to behave the same...

nicholasralabate
Sorry for the necro, but what does (FA) mean?

Should be Float Array. I could be wrong, but I'm pretty sure that that's what it is.

As for the difference between a vector3 and a 3-float array, here are some comments [www.sidefx.com].