1.Enter the ceiling custom then double-click the wall to access the 2D ceiling design interface

2.Use the “straight line” tool from the top menu to draw a straight line connecting to both end walls.

3.Click to select the line, right-click on it, and choose “Split.”

4.After splitting, the line becomes two segments. Right-click each segment and convert them to arcs.

5.Return to the 3D/Walkthrough view, find the light tube in the section library on the left, and drag it onto the line.