VXZOFFSET-bgol (Uniform Vertex Elevation Offset)

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 uniform vertex-elevation offset 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

VZO applies a uniform elevation offset, add or subtract a fixed value, to every vertex of a selected 3D polyline at once. Native "change elevation" workflows only work cleanly on entities with a single uniform Z, but a 3D polyline typically has a different Z value at every vertex. VZO fills that gap by shifting the whole polyline as a rigid body in the Z direction, preserving its shape.

How to Use

1. Load VXZOFFSET-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type VZO at the command line and press Enter.
3. Select the 3D polyline you want to shift.
4. Enter the elevation offset when prompted, a positive number raises the polyline, a negative number lowers it (e.g. 2 or -0.5).
5. Every vertex's Z value is shifted by the same delta; relative elevation differences between vertices are preserved exactly.
6. The command reports how many vertices (or the elevation value, for an LWPOLYLINE) were updated.

Why Use It

• Systematic correction in one step, fix a benchmark correction, a datum shift, or an instrument offset across an entire 3D polyline instead of editing each vertex manually via grips/Properties.
• Shape-preserving, the polyline's profile is unchanged; only the whole line moves up or down as a rigid body in Z.
• Faster and safer, much quicker and less error-prone than manually opening the Properties palette and editing dozens of individual vertex Z values one at a time.

Where to Use It

• Correcting a datum/benchmark shift across an entire surveyed breakline, drain invert, or pipe alignment modeled as a 3D polyline.
• Adjusting design 3D polylines (e.g. a proposed pipeline or channel centerline) when a global elevation offset is required (e.g. "raise the whole invert by 150 mm").
• Any land survey or infrastructure drawing workflow where 3D polyline elevation data needs a systematic, uniform correction.

Notes

• Works on legacy 3D POLYLINE entities (shifting each VERTEX sub-entity's Z) and on LWPOLYLINE entities carrying a single elevation value (DXF group code 38).
• Entering an offset of 0 is valid but has no visible effect, useful as a quick way to confirm the command runs without altering geometry.
• 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.