# Compute centerline

You can compute the centerline of a pipe, cylinder or ducting in a BIM model. The software computes a polyline that runs along the center of the surface.

1. You can choose whether selecting surfaces in the map selects Individual faces or selects the Whole object. To change the Surface selection mode, tap and select your preferred Surface selection mode. See BIM model selection mode.

2. In the map, tap the surface to select it.

3. Tap and hold in the map and select Compute centerline.

   The computed centerline is shown in the map.

4. Enter the Polyline name.

5. If required, enter the code for the line in the Code field.

6. Tap Store.

When the Surface selection mode is set to Whole object, any hidden parts of the object, such as parts that are used to join the object to another object, are also selected. This may result in a longer centerline for the surface than when the Surface selection mode is set to Individual faces.