Aryan,
Did you see the test in VTK
https://gitlab.kitware.com/vtk/vtk/-/blob/master/IO/Cesium3DTiles/Testing/Cxx/TestCesium3DTilesWriter.cxx?ref_type=heads
and the blog:
https://www.kitware.com/3d-tiles-generation-using-vtk/
Both show you examples of how to use the writer. I’ll try to take a look at your code.
Dan