Polygon model files (.ply) can be generated from many other 3D models, including the XGL 3D CAD model files (.xgl). This can usually done with some sort of dedicated converter software like the Online 3D Model Converter and possibly also other.
Convert XGL 3D CAD model to Polygon graphics.
We found 2 software records in the database related to .xgl to .ply file format conversion.
Microsoft Windows software - convert xgl to ply on Windows
A 3D CAD translation softwate
Convert from xgl file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned xgl to ply. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
On-line services software - convert xgl to ply on web
A free online 3D model conversion service