EXTFIX-bgol (Reset Non-Default Extrusion Direction)

Command Type: AutoLISP routine (works in AutoCAD, BricsCAD, ZWCAD and most AutoLISP-compatible CAD platforms)
Developed by: BGol Community, bgol.in

Inspired by the general concept of extrusion-direction recovery utilities used in CAD drawing-repair workflows. This is an original, independently written routine, new file name, new command name, new source code, created so the CAD community has a free, editable, open-source alternative.

Overview

Some drawing files contain entities that behave "weirdly" because they were created in a non-default User Coordinate System (UCS) and carry a nonzero extrusion direction (DXF group 210). This UCS/extrusion mismatch can cause entities to display or transform unexpectedly. EXF scans the drawing and resets any non-default extrusion vector back to the normal (0, 0, 1) value, which can recover entities affected by this specific issue.

How to Use

1. Load EXTFIX-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type EXF at the command line and press Enter.
3. The routine automatically scans every entity in the drawing and resets any non-default extrusion direction to normal, no further input is required.
4. Running this on a normal, unaffected drawing produces no visible change (and the routine will report that no non-default extrusions were found). Running it on a drawing affected by this issue recovers most affected entities to normal behavior.

Why Use It

• Drawing Recovery, fixes entities that behave incorrectly due to a specific but common corruption pattern (non-default UCS extrusion), restoring normal, predictable behavior.
• Safe on Unaffected Drawings, running it on a normal drawing causes no visible change, so it can be applied broadly as a diagnostic/ preventive step without risk of altering already-correct drawings.
• Diagnoses a Root Cause, directly addresses a known, previously hard-to-diagnose source of "weird" entity behavior in received drawing files.

Where to Use It

• Diagnosing and repairing drawings received from external sources (clients, other firms, different CAD software) that exhibit unexplained entity behavior, entities snapping incorrectly, drawing at unexpected angles, or interacting oddly with other commands.
• A standard "first pass" recovery step when a drawing is suspected to be corrupted, since it's safe to run on unaffected files.

Notes

• Uses a small tolerance (1e-6) when comparing the extrusion vector to (0, 0, 1) so floating-point rounding doesn't cause false positives.
• Entities that cannot be modified (e.g., on a locked layer) are counted separately and reported, rather than silently failing.
• Source code is fully open, feel free to study, modify, and redistribute it under the same open, free-for-all spirit.

Credits

Developed and shared for the CAD community by BGol Community. Website: https://bgol.in/ Free and open-source, use it, modify it, share it, for personal or commercial work alike.