Function: mergeMaterialXPackages()
mergeMaterialXPackages(
packages):MaterialXPackage
Combines multiple packages into one, root document first. Resources are concatenated, renaming (and rewriting references to) any archive path that collides with one already taken. Throws if two inputs share a top-level element name (materials, nodegraphs, etc.), since MaterialX names must be unique within a document and there's no safe way to rename one without also rewriting every reference to it.
A single-package input is returned as-is.