Hello, Nathan,
Stanford PLY file format doesn't define a single standard for storing texture UV coordinates inside the PLY file.
Different programs use different names for storing UV coordinates:
Blender: s, t (with a note that u, v should be used in the future versions)
MeshLab: texture_u, texture_v
PhotoScan: u, v
This leads to incompatibilities when loading PLY files exported with a different program.
It is possible to change the names in the PLY file header using a text editor. Not every text editor is suitable, as the majority of the data in PLY files is stored in binary format and should be left unchanged. The internal text editors of the FAR file manager worked for me.
After these changes MeshLab loads PLY files with texture coordinates properly.
The second problem is loading a texture itself. As the PLY file doesn't store internal reference to the texture file, the texture should be loaded manually. Unfortunately, I was unable to find how to load a texture from a specified file in MeshLab.
We will add the option to select the names for storing UV coordinates in the next PhotoScan version.
With best regards,
Dmitry