Pen Curve — draw and edit Bézier curves

What does this tool do?

Pen Curve is a Corel-style Bézier pen inside SketchUp: place corner nodes, smooth nodes with handles, and re-shape the curve at any time. The result is an ordinary welded curve on a plane — usable by every other tool (Make Face, Contour, push/pull…).

Use it when you need to:

Draw smooth curved outlines (rounded tabletops, ornaments, chamfer lines) instead of chaining arcs.
Bend a straight line into a curve passing through an exact point.
Re-shape an existing curve by dragging its nodes and handles.

Drawing a new curve

Click the Pen Curve icon. The drawing plane is the face under the cursor at your first click — with no face there, it falls back to the ground plane through that point.
Click – place a corner node (polyline-style).
Click + drag – place a smooth node with two mirrored handles; drag to aim the tangent. Hold Alt while dragging to break the corner (independent handles).
Click the first node – close the curve (a closed curve auto-creates a face). Clicking another pen curve's end node joins the two paths.
Enter or double-click – finish the curve. Backspace – drop the last node. Esc – cancel the whole curve.

Corner nodes, a smooth node with gray handles, the pink curve

Editing a drawn curve

Click a pen curve to enter edit mode (pink curve, blue square nodes, the selected node in orange):

Drag a node – move it; drag a handle – change the curvature (hold Alt to break the corner).
Drag a segment's body – bend the whole segment through the cursor.
Double-click a segment – insert a node there.
Double-click an end node – continue drawing from that node.
Delete – remove the selected node. Esc – leave edit mode.

Every drag is its own Undo step.

Edit mode: the orange selected node, drag the handles to reshape

Bending lines and converting

Press + drag a plain straight line – bend it into a curve through the cursor; after release it stays open for editing. (A plain click on a line starts drawing from that point instead.)
Double-click a plain line – the whole connected line run (polyline, rectangle…) becomes one pen path with corner nodes at every vertex, plus a new node where you clicked, open for editing. The run stops at branches, arcs/curves, or non-planar sections.
Right-click menu “Convert to pen curve” – when the selection holds convertible lines/arcs/curves: each connected run becomes one pen path (lines keep corner nodes, arcs become exact Bézier pieces of ≤90°, other curves keep their vertices). Non-planar runs are skipped and reported on the status bar.

1: drag the middle of a straight line. 2: it bends through the cursor into a pen curve

Segments

The Segments HUD chip (default 12, max 200, remembered between uses) controls how finely the curve is built into edges. Type a number and press Enter to set it quickly, or click the chip to enter one.

Keyboard

Alt (held while dragging) – break the handle pair.
Enter / double-click – finish the curve being drawn.
Backspace – drop the last node while drawing; Delete – remove the selected node while editing.
Esc – cancel drawing / exit editing.

Common problems

“Could not convert a solid's edge…”: only loose lines lying on one plane can be bent/converted — edges belonging to a solid, or runs wandering through 3D, are refused.
No face appeared: only a closed curve auto-creates a face — click exactly the first node to close it.
A smooth node kinked: Alt was held by accident and split the handles — drag a handle again without Alt to re-mirror them.
Curve too jagged or too heavy: adjust the Segments chip — fewer segments look angular, too many make the model heavy.