How to Draw 3D Polylines in BricsCAD

Quick answer: A 3D polyline is composed of straight linear segments in genuine 3D space, no arcs, unlike a regular polyline. Linetypes behave differently on 3D polylines too, they draw uninterrupted by default, and PLINEGEN (which fixes this for ordinary polylines) has no effect on them at all.

Finding the 3D Polyline Tool

The Draw menu, the Polylines toolbar (not the general Draw toolbar), or the Draw ribbon panel.

Drawing a 3D Polyline: General Procedure

1. Launch 3DPOLY. You’re prompted for the start of the polyline, or to choose Follow, defaulting to your last point if you just press Enter.
2. Specify a point. You’re prompted for the next point.
3. Specify a point. You’re prompted for the next point, or to choose Close or Undo.
4. Either choose Close to connect back to the start (with just three points so far, this creates a planar triangular 3D polyline), or specify another point.
5. Either choose Close, or specify another point.
6. Keep specifying points, or press Enter to stop.

Linetypes on 3D Polylines

A 3D polyline with an assigned linetype draws with an uninterrupted pattern by default, the dashes and gaps don’t actually show. To make the linetype visible, set LINETYPE3DPLINE to 1.

Worth knowing specifically: PLINEGEN, which controls whether an ordinary polyline’s linetype generates vertex to vertex or end to end, has no effect on 3D polylines at all. No other setting changes how the linetype pattern renders on one, only LINETYPE3DPLINE does.

Editing a 3D Polyline

Select it, and its properties appear in the Properties panel under Misc:

• Fit/Smooth: choose None, Cubic, or Quadratic. Cubic and Quadratic both convert the display into a spline representation of the 3D polyline.
• Closed: set to No to remove the closing segment from an otherwise closed 3D polyline.

Frequently Asked Questions

Can a 3D polyline include curved arc segments like a regular polyline can? No, a 3D polyline is composed of straight linear segments only.

Why doesn’t my 3D polyline’s linetype show dashes and gaps? By default, linetypes draw uninterrupted on 3D polylines. Set LINETYPE3DPLINE to 1 to make the pattern actually visible.

Does PLINEGEN affect 3D polylines the same way it affects regular polylines? No, PLINEGEN has no effect on 3D polylines at all. Only LINETYPE3DPLINE controls how their linetype pattern renders.

Can I turn a 3D polyline into something resembling a spline? Yes, set its Fit/Smooth property to Cubic or Quadratic in the Properties panel, either one creates a spline representation of it.