ARCFLAT-bgol (Decurve a Polyline / Remove Arcs)

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 arc-removal / un-fillet utilities used in CAD/survey drafting. 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

AFLT removes arc segments from a selected polyline by clearing every non-zero bulge value, converting each arc into a straight chord between its two endpoints. Unlike AutoCAD's native PEDIT → Decurve option, this also works on arcs created by FILLET, which the native option cannot process.

How to Use

1. Load ARCFLAT-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type AFLT at the command line and press Enter.
3. Select one or more polylines containing arc/fillet segments.
4. Press Enter to finish the selection.
5. A new straight-segment-only polyline is created for each selected entity on a dedicated layer, BGOL-AFLT (colour green). The original polylines are left untouched.

Why Use It

• Handles Fillet arcs, fills a real gap in AutoCAD's native Decurve option, which cannot process FILLET-created arcs.
• Simple, select-and-run workflow, accessible to users of any skill level.
• Prep step for other tools, a straight-segment-only polyline is easier to measure, edit, export, and process with other vertex-based routines that assume straight segments.

Where to Use It

• Preparing filleted/rounded polylines (rounded building corners, rounded road edges) for tools or export formats that don't handle arc geometry well.
• Simplifying complex drawings for clarity and easier downstream editing where arc geometry isn't needed.
• Any workflow needing straight-segment-only polylines as a prerequisite for other vertex-based processing.

Notes

• The default behaviour clears each bulge value, replacing every arc with a straight chord between its original two vertices (a fast, simple approximation). For a shape-preserving result that samples multiple points along each original arc instead, adapt BGOL:AFLT-FlattenOne to use vlax-curve-getPointAtParam.
• Works on LWPOLYLINE entities; the original selected polylines are not deleted, so you can compare or remove them manually afterward.
• 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.