> For the complete documentation index, see [llms.txt](https://nx.docs.scailable.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nx.docs.scailable.net/ai-manager-v6.1.4/ai-manager-plugin/configure-the-plugin/postprocessors/line-crossing-detection.md).

# Line Crossing Detection

Line crossing detection can be used to detect or count objects which cross a defined line. The postprocessor works by tracking objects through the frames, and detect when this object crosses a line, and the direction.

<figure><img src="/files/oMX2nWzHkfDxDHdPnA9S" alt="Line Crossing Detection postprocessor settings panel"><figcaption><p>Line Crossing Detection settings</p></figcaption></figure>

Use the Nx Meta interface to draw a line on the video frame and click **Apply** for changes to take effect.

<figure><img src="/files/9UfS07UiENgSYRA4927E" alt="Drawing a crossing line on the video frame in the Nx Meta interface"><figcaption></figcaption></figure>

When a crossing is detected, an event is generated. This event can be configured to trigger any action, see [adding event rules](/ai-manager-v6.1.4/ai-manager-plugin/configure-the-plugin.md).

<figure><img src="/files/VauzHmDThPR7dCVhdXZR" alt="Event Rules configuration for a Line Crossing Detection event"><figcaption><p>Line Crossing Detection event configuration</p></figcaption></figure>

Select the Line Crossing Detection postprocessor and click **Apply** before creating the event.

Line Crossing Detection is compatible with any model which generates bounding boxes.