# Small screen-space "dash" appears at curve midpoint after cloning a Markups curve (Markups → Clone)

**URL:** <https://discourse.slicer.org/t/small-screen-space-dash-appears-at-curve-midpoint-after-cloning-a-markups-curve-markups-clone/48374>\
**Category:** Support\
**Created:** [October 1, 2026, 2:51pm UTC](https://discourse.slicer.org/t/small-screen-space-dash-appears-at-curve-midpoint-after-cloning-a-markups-curve-markups-clone/48374 "2026-10-01T14:51:40Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![evan1](https://avatars.discourse-cdn.com/v4/letter/e/e47c2d/32.png) [@evan1](https://discourse.slicer.org/u/evan1)\
**Post date:** [October 1, 2026, 2:51pm UTC](https://discourse.slicer.org/t/small-screen-space-dash-appears-at-curve-midpoint-after-cloning-a-markups-curve-markups-clone/48374/1 "2026-10-01T14:51:40Z")

</div>

**Environment:** 3D Slicer 5.12.3, Windows 11

**Summary**

After cloning a Markups curve via the Markups module (right-click a curve node in the list → **Clone** ), the cloned curve displays a small horizontal line (“dash”) at (or very near) the **curve’s midpoint**. The original curve does not show it. It reproduces reliably, including with a freshly drawn dummy curve (4 arbitrary points).

The midpoint location is confirmed by the control point counts: most of my curves have 4 points, and their dash sits next to the **second** control point; one curve has 5 points, and its dash sits next to the **third** control point (its exact middle). So the dash tracks the curve’s midpoint, not a specific control point.

 ![Screenshot 2026-09-30 170005](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/1/d/1da2001947ac2ba7f62fe0beefdd03492b425c8d.png)

 ![Screenshot 2026-09-30 131415](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/c/7/c7aaa2886308a9bed92156d3c19f1bf124741de6.png)

**Observed behavior**

- The dash is always screen-horizontal and projects to the right of the curve regardless of camera angle — suggesting a 2D/screen-space actor rather than 3D scene geometry. It is also always the same pixel size no matter how much I have zoomed in or out on the 3D scene.

- It follows the curve’s midpoint wherever the geometry goes: moving any control point — including programmatically via `SetNthControlPointPosition()` — moves the dash along with the curve. Initially it looked tied to control point 2, because on my 4-point curves the midpoint happens to sit right next to that point; the 5-point curve (dash at its middle point) confirms it tracks the midpoint.

- It appears immediately upon cloning, before any geometry or display changes.

- It highlights (active color) together with the curve when hovering the curve, but is not individually clickable/selectable.

- Toggling the clone’s display node visibility hides the dash together with the curve; restoring visibility brings it back.

**What I ruled out** (all compared between original and clone, all identical):

- Display node properties: point label visibility (off), text scale (0), glyph type (Sphere3D), glyph scale, line thickness, curve line size mode, fill/outline/occluded visibility, rotation/translation/scale handle visibility, interaction handle scale.

- No measurements exist on either node (“no measurements” in the Markups Measurements section).

- Per-point properties: labels, position status (all defined), locked and selected flags — identical on all 4 points of both nodes.

- Node class is identical (`vtkMRMLMarkupsCurveNode`) and the two nodes have **separate** display nodes (not shared).

- Changing the curve type (spline → polynomial / Kochanek) does not remove the dash.

- Changing point spacing/geometry (including widening the gap between points 1 and 2) does not remove the dash.

**Renderer inspection**

Iterating the 3D view renderer’s visible props near the curve shows **two** `vtkSlicerCurveRepresentation3D` instances with nearly identical bounds:

```auto
3D: vtkSlicerCurveRepresentation3D | bounds: [6.6, 15.3, -79.2, -67.8, -221.2, -211.8]
3D: vtkSlicerCurveRepresentation3D | bounds: [5.8, 14.3, -86.6, -73.5, -242.8, -233.0]

```

(The bounds above reflect the curve after control point positions were moved during testing.)

**My chatbot’s suspicion**

The Markups “clone” operation appears to leave behind (or create an extra) curve widget/representation in the view, which renders a small screen-space element anchored to the **curve’s midpoint** — the same location where the markups interaction-handle widget places its center elements. Because this element is drawn by a stale/duplicated representation rather than the live display node, changing display properties (handle visibility, glyph type, labels, measurements) has no effect on it. It could be a degenerate center/handle/label actor that the duplicated representation never cleans up.

**Questions**

1. Is this a known issue with the Markups “clone” operation?

2. Is there a workaround to remove the stray element without deleting and recreating the cloned nodes?

3. Is there additional diagnostic information I could collect that would help pin this down (e.g., a way to identify which of the two `vtkSlicerCurveRepresentation3D` instances draws the dash)?

I’ve checked the 5.12 release changelog including the 5.12.4 patch notes and found no mention of a related fix. The new arrow glyph types (Arrow2D etc.) are not in use here — both nodes’ glyph type is Sphere3D.

Thank you!