MultiPLine (MPL) — polyline-based MLINE replacement with per-line layers, presets, and auto-sync [Free + Pro]

Saturday at 07:01 PM

Hi all,

I've been a lurker on CADTutor for years and learned

a lot from this community, so I wanted to share

something I built and get feedback from people who

actually know LISP.

Background: I'm a civil CAD drafter working on US

land development projects — grading, drainage,

easements, corridors. MLINE has always been the

tool I wanted to use for drawing parallel offset

lines but couldn't, mainly because the objects are

locked, there's no lineweight control per component,

and the .mln style management across a team is a

nightmare. So I wrote a replacement.

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WHAT IT DOES

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Command MPL works like PLINE — you draw a centerline

and it generates a set of configurable parallel

LWPOLYLINEs around it. Every satellite line is a

real polyline: fully grip-editable, trimmable,

offsettable, joinable. No locked geometry, no

exploding required.

Each satellite line carries its own:

- Offset distance (positive = left, negative = right)

- Layer (Pro version)

- Color, linetype, lineweight, linetype scale

Configuration is handled through a DCL dialog

(MPLEDIT). Settings save as user defaults and,

in the Pro version, as named presets stored in

%APPDATA%\MplineAuto\presets.dat.

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TWO VERSIONS

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Lite (free .lsp):

- MPL, MPLEDIT, MPLSYNC

- Manual sync after edits — run MPLSYNC,

window-select the group, done

- Groups are tracked via XDATA (app tag: MPLINE_PIPE)

Pro (compiled .vlx, $29.49):

- Everything in Lite plus:

- Command reactor for auto-sync — watches masters

before/after every command, diffs vertex lists,

rebuilds only what changed

- Named preset library with Save/Update/Delete

from the dialog

- Per-satellite layer assignment

- MPLADD — promote existing LWPOLYLINEs or LINEs

into MPL groups

- MPLON / MPLOFF — toggle reactor at runtime

- XDATA app tag: MPLINE_AUTO

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IMPLEMENTATION NOTES

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The interesting part was the Pro reactor. I went

through a few approaches before landing on a global

command reactor that snapshots the master cache

before a command fires and diffs it after. This

avoids object reactors entirely (which caused IDispatch

arity issues in testing) and means the reactor

doesn't interfere with Express Tools or COPY/MIRROR

operations on non-MPL geometry.

Groups copied with COPY or MIRROR produce new masters

on the next MPLSYNC call — the reactor doesn't

auto-register copies, which is intentional to avoid

unexpected geometry multiplication.

Happy to discuss the approach if anyone has thoughts

or has solved similar problems differently.

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LINKS

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Video walkthrough: https://youtu.be/DXpyy1JWtXs

Free Lite download:

https://skillamplifier.gumroad.com/l/hgpujs

Pro listing:

https://skillamplifier.gumroad.com/l/nsidsv

Blog post with full documentation and use cases:

https://skillamplifier.wordpress.com/2026/05/16/multipline/

Full disclosure: I'm the developer. Posting here

because I'd genuinely value feedback from experienced

LISP users, and the Lite version is free so there's

no risk trying it.

Thanks for any thoughts.

Zlatislav

2026-05-18T18:05:58Z

https://www.lee-mac.com/mpline.html FYI - not to detract from your work, which I'm sure was extensive.

Edited 6 hours ago by pkenewell

2026-05-19T00:23:50Z

Just a couple of comments have this, type 2,4,-3,-4 and so on, draws multiple plines, as many as you type in one go.. Have a drag line over existing multi offsets and get all offsets and layers, so can make another pline without user input.

Also what about Bricscad users ? Plenty of us here as well as other software.

Oh yeah look at this image you draw a "WALL" that is multiple lines and on correct layers, predefined layers that are named in a txt file, wont go into how we made that work other than variable = layer name.

Not sure that the task really warrants a VLX and a cost when there is software out there for the task and its free. I know from experience trying to sell software is extremely hard, as per draw house program some 130 lisps.

Do you have something similar to the attached DOCX, showing what you have as say a package, most programs are free and open source some have a cost as need to be customised for clients. There is more scope for users to buy a package rather than just one program.