GLOSSARY
PLY File
PLY is a flexible 3D format developed at Stanford. It can store either point clouds or meshes, with per-vertex color, normals, and arbitrary custom properties.
Definition
PLY was created in the mid-1990s for the Stanford 3D Scanning Repository. The format has a small header that declares which properties each vertex and face carries — XYZ position, RGB color, normal, confidence value, anything — followed by the data, in either ASCII or binary form.
That extensibility is the reason PLY persists: photogrammetry tools (Meshroom, RealityCapture), depth sensors (Kinect, iPhone LiDAR), and Gaussian splatting trainers all output PLY because they need to carry custom per-point data that STL or OBJ cannot represent.
Why it matters
If you scan a real object, the first artifact you get back is almost always a PLY. From there you can clean and convert to a printable mesh in MeshLab or Blender. PLY is also the de-facto export format for trained Gaussian splat scenes — millions of colored, oriented points each with a covariance matrix.
Common confusion
Slicers do not read PLY. You have to convert to STL (or 3MF) first, and you have to make sure the PLY actually has faces — many PLY files are point clouds with no triangulation, which means there is no surface to print.
PLY supports per-vertex color, but most printers cannot use it directly. For multi-color FDM you still need 3MF with material assignments.