Module write 

Writing STEP: the document’s products, assemblies, colours and B-rep.

The mirror of the reader, and deliberately written against the same vocabulary: every entity this writer emits is one the reader parses, so writing what was read and reading it back is the honest round-trip test. AP214’s schema name goes in the header; the entities used are the common AP203/AP214/AP242 core.

Geometry is written in world coordinates: every face, edge and vertex is transformed through its occurrence’s own placement chain before it is serialized, and shared nodes are deduplicated per placement: a prism’s bottom and top edge are one node at two locations, and the file needs both. Surfaces the format has no analytic name for (extrusions, revolutions) go out as their exact rational B-spline patches (§3’s conversion), so nothing is fitted on the way out.

Functions

write_step

Write a document as a STEP exchange file.