# Polyline 2D

A **Polyline 2D** is an annotation tool used to draw a series of connected straight lines (segments) on a 2D image. It consists of multiple points (or nodes) that define the shape, allowing annotators to mark irregular or elongated objects with more precision.

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## Use Case

The polyline 2D tool is especially useful for annotating objects like road lanes, wires, edges of buildings, or boundaries that follow a path. By adjusting the points, annotators can capture the shape and position of linear or curvilinear objects within an image, providing valuable data for training computer vision models in tasks such as lane detection or object tracking.

{% hint style="info" %}
Polyline 2D can be created only in camera sensors.
{% endhint %}

<figure><img src="/files/ol2LqIz9Aq3mmy4OjNE9" alt=""><figcaption></figcaption></figure>

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## Create Polyline 2D

1. Click on the '+' icon of the class from the [class list](https://docs.imerit-prod.io/annotation-tool/drawing-tools/pages/t1P8d2reKe3nZWAkN2Kh#id-3.-class-list)

2. Select Polyline 2D from the drawing tool list.

   <figure><img src="/files/wlIEWOR2Xp6xG443Y1sU" alt="" width="375"><figcaption></figcaption></figure>

3. The cursor pointer shows a yellow circle marker while hovering over the image.

4. Start the polyline segment by making the first click to place the initial point. Move the mouse to the next desired location, and a line extending from the initial point will dynamically follow the cursor.

5. User continues following the path by left clicking and creating vertices/points where needed.&#x20;

6. To end the annotation, ensure that the last vertex is created via right-click.
   * `Right-click` will introduce a point on the location.

<figure><img src="/files/bMGicSecnCwxK6GvYrhp" alt=""><figcaption></figcaption></figure>

7. Enter the [annotation details](https://docs.imerit-prod.io/annotation-tool/drawing-tools/pages/rZkaXOIF73IyAuNXrSbe#id-6.-annotation-detail-input).
8. The saved instance will appear on the [class list](https://docs.imerit-prod.io/annotation-tool/drawing-tools/pages/t1P8d2reKe3nZWAkN2Kh#id-3.-class-list) with a 2D icon (RoadLanes\_15 #3) next to the instance name to denote it is made in the image sensor. It shares the same ID as the instance present in the point cloud of the same object (RoadLanes\_15).

<figure><img src="/files/VZSZjBSX24ncD3gqWuGc" alt="" width="344"><figcaption></figcaption></figure>

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## Modify Polyline 2D

* Modify the polyline 2D by selecting the node and dragging it.
* Remove a vertex by dragging it to it's consecutive vertex.
* Add a vertex by hovering over one segment.  This segment turns yellow and a pink point appears helping the user visualize where the point will be created.

<figure><img src="/files/Sdt0cL8cgAwXxeItuQ6c" alt=""><figcaption></figcaption></figure>


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