PLY or "Polygon File Format" is an extension used for storing data collected with 3D scanners. It is also known as "Stanford Triangle Format" because it was created at Stanford University in the mid-1990s, with a design inspired by Wavefront's OBJ vector format. A PLY file contains a 3D description of an object through a list of nominally flat polygons, as well as info regarding color, transparency, textures etc.
The quick and simple way to handle your files is to get a quality piece of software, such as reaConverter. This software is extremely efficient in managing a wide range of batch conversions. As you will soon realize, reaConverter will help you avoid spending countless hours trying to figure out how to convert multiple PLY files as once.
JPEG JPG PNG GIF TIFF TIF BMP ICO EMF WMF AI PDF EPS PS EPI WEBP WEBPLL JP2 PCX TGA DWG DWF DXF DGN WMZ CGM DRW SHP GBR PCT MIF PLT PCL SVG WPG CIN DCX DIS HRU MTV PRC RAD PIC RLA QRT SGI XBM XPM SWF CAL FAX FITS PSD PGM JXR BPG STL APNG DDS SVGZ CG4 FLIF STEP STP AVIF