CAD Compare

Version and capabilities of this CAD comparison server. Call it once if you need to know which file types are supported.

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Compare two STEP part files (single parts, not assemblies) and say whether they are the same part. Use it when the user asks whether two CAD files differ, what changed between two versions of a part, or whether a part was only moved or mirrored. The files are read locally and never uploaded. Returns verdict (same / moved / different) and, when different, the changed features with sizes, e.g. {type: "through_hole", change: "modified", attr: "diameter", from: 6, to: 6.5, location: [150, 90, 10]}. Typical time: under a second for simple parts, 5–15 s for parts with several hundred faces. Multi-body parts (several solids in one file) need CAD Compare Pro; the free version returns license_required for them. Report warnings to the user; they say when the result needs care.

Geometric fingerprint of one STEP part, independent of position and orientation (volume, area, principal sizes, face types). Use it to recognise the same part under different file names or to sort many files before comparing pairs; two parts with clearly different fingerprints are different, similar fingerprints still need compare.

Compare two versions of a STEP assembly: which parts were added, removed, renamed or replaced, which parts changed shape (with the changed features, as in compare), quantity changes, and which parts or subassemblies moved or changed parent. Use it when the files are assemblies (compare reports them as unsupported) or the user asks what changed in a product structure. Also works when one side is a single part. Files are read locally and never uploaded. Typical time: a few seconds for tens of parts, up to a minute for hundreds. If warnings contains not_all_parts_compared, say so and offer to rerun with a higher max_detailed_parts. Requires CAD Compare Pro (see describe → license).

Find STEP part files in a folder that are the same part: identical copies, re-exports, or the same part moved or rotated, whatever the file names. Also reports left/right (mirror-image) pairs. Use it to clean up a messy project folder, find which supplier file matches which drawing, or avoid making the same part twice. Files are read locally and never uploaded. Only files whose fingerprints match are compared in full, so large folders are feasible; typical time is 0.1–1 s per file plus 0.3–5 s per comparison. Assemblies are skipped (listed in skipped). Requires CAD Compare Pro (see describe → license).

Write a comparison report of two STEP files (parts or assemblies) as a self-contained HTML file that can be printed to PDF: verdict, the list of differences in plain language, key figures, and for assemblies the changed, added, removed and moved parts. By default it also contains an interactive 3D view (rotate, zoom, measure; click a difference in the list to show it), which works offline in any browser. Use it when the user wants something to keep, send to a colleague or supplier, or attach to a change request, or wants to see the change in 3D. It writes one file on this computer and never overwrites one unless overwrite is true. Returns the path and a file:// url; give the user the url as a link to open it. Requires CAD Compare Pro (see describe → license).

Picture of where two STEP parts differ, as PNG images you can look at: an overview and, when there are differences, a close-up. Coloured as in the CAD Compare viewer: faces identical in both grey, differing faces of A red, of B green, and numbered markers whose meaning is in legend (the same differences compare lists). For parts that were only moved or mirrored, B is shown with A's outline on top. Use it when the user wants to see the change, or to check a result visually. Rendered locally without a GPU; files are never uploaded. Requires CAD Compare Pro (see describe → license).