How to remove border on creating (rectangle) custom mesh/

The 3D Text Insertion example is the same as I had referenced in your previous post. Are you not able to view this example? The entire code for this example is provided in HOOPS_Communicator_2024.X.0\web_viewer\examples\scripts\examples\text_insertion.js.

A meshData object does not have a polyline by default. So somewhere in your code, you are calling the addPolyline function.