MIDBLK-bgol (Insert Block at Segment Midpoint)

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 per-segment midpoint block insertion used in landscape and planting layout 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

IBSM inserts a copy of a chosen block at the true midpoint of every individual segment of a selected polyline, no matter how unequal the segment lengths are. AutoCAD's native MEASURE places blocks at a fixed distance, and DIVIDE splits the whole polyline into equal parts, neither can target the midpoint of each separate segment. IBSM solves that gap directly.

How to Use

1. Load MIDBLK-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type IBSM at the command line and press Enter.
3. Select the polyline whose segments should each receive a block.
4. Type the name of an existing block in the drawing when prompted.
5. A copy of that block is inserted at the midpoint of every segment of the selected polyline, placed on a dedicated layer, BGOL-IBSM (colour green).

Why Use It

• Fills a native gap, neither MEASURE nor DIVIDE can target the midpoint of each individual segment when segment lengths vary; IBSM does this directly.
• Time savings, automates precise per-segment midpoint placement instead of manually snapping to each segment's midpoint one at a time.
• Consistency, every segment gets exactly one block, evenly centered, regardless of how many segments or how irregular their lengths.

Where to Use It

• Landscape and planting layout drawings, placing trees, shrubs, or other repeated symbols evenly along a path or boundary line.
• Placing utility markers, posts, or fixtures at the midpoint of each fence, pipe, or cable segment.
• Any drafting task needing a symbol centered on each segment of a multi-segment polyline, rather than at fixed distance intervals.

Notes

• Works on LWPOLYLINE entities. Segments containing an arc (bulge) are treated by their chord midpoint for simplicity.
• Block scale and rotation default to 1/1/0; edit *bgol-ibsm-scale* and *bgol-ibsm-rot* near the top of the .lsp file to change the defaults.
• Closed polylines also receive a block on the closing segment between the last and first vertex.
• 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.