poka.sh

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STEP

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Step Preview.

At a glance
Original creator ISO technical committee TC 184, subcommittee SC 4 (industrial data)
First published 1994
Purpose A plain-text file format for transferring product and engineering data described by an EXPRESS schema between systems.
Extensions .step
Poka parser poka-step
Viewer poka-3d-viewer
Depth tier Parser with a shared viewer (see Depth tiers)
Breadth tier B3 Core (see Breadth tiers)

How much Poka reads

B3 Core. Only the main content type or types are decoded (for example geometry but not materials, layers or annotations, or only one version family). The list of gaps is substantial.

Confidence: medium (the reviewer read the code). Basis: Reviewed 2026-10-16: the poka-step module, the truck-stepio table it relies on and the three corpus .step files (AP203 and AP214; none has assemblies, colours or tessellated geometry); the crate has no tests of its own. The tier covers files up to 1 MiB (the geometry is drawn as one mesh); a larger file is shown as a text summary only, which would be B4. AP242 is unverified.

What Poka does not read

  • Assemblies and part placement
  • Colours and styling
  • Part names, units, materials and annotations
  • Faceted, tessellated and wireframe geometry
  • Files over 1 MiB (shown as a text summary only)
  • More than 64 shells or 300,000 triangles
  • Everything after the first data section

Background

The Library of Congress describes the STEP-file as ISO 10303-21, first edition 1994, second edition 2002, third edition 2016. Common extensions are .step, .stp and .p21; Poka lists .stp as its own STP row. Application protocols such as AP203, AP214 and AP242 define what a file contains. Poka tessellates the open or closed shells it finds and shows them as one mesh within a time budget, so a large assembly may be cut short; a file over 1 MiB is shown as a text summary only. Assemblies, colours, part names and units are not read. No corpus sample uses AP242, so that protocol is unverified.

Libraries

Libraries Poka uses or has assessed for this format, with the status, licence and language the registry records.

  • truck-meshalgo (used; Apache-2.0; Rust)
  • truck-stepio (used; Apache-2.0; Rust)
  • oxideav-step (candidate; MIT; Rust; https://github.com/OxideAV/oxideav-step) — v0.0.1; faster than poka-step on files of 70 KB or more; changes every STEP preview; assemblies not placed

Software that uses it

  • STEP (ISO 10303)

Sources