You can probably convert polygon graphics (.ply) to similar ASCII files that sometimes have txt suffix. Probably something very specific, but doable with programs like Blender or similar. If you are looking for something specific, please let us know in the discussion below.
Convert Polygon graphics to MilkShape 3D ASCII file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert ply to txt on Windows
A very popular free program used for work with 3D graphics
Convert from ply file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.