PLY

Files are arranged in the form of a header, in which the elements of the mesh and their types are determined, and the list of the elements following them. Elements are usually vertices and faces, but other entities, such as edges or triangle strips, may be included.

The header for both ASCII and binary is ASCII text. Only the numerical data following the heading differs between versions. The heading always starts with a line containing the word

  ply

that identifies the PLY file format. The second line displays which version of the PLY format is used:

  format ascii 1.0
 format binary_little_endian 1.0
 format binary_big_endian 1.0

At the moment, 1.0 is the only used version of the format.

Comments can be placed in the header using the word comment at the beginning of the line. The entire line after this word will be ignored during import:

  comment This is a comment!

The element keyword introduces a description of which particular data item is stored in the file, as well as the number of these items. The example below describes that the file contains 12 vertices, each of which is represented as three floating-point numbers:

  element vertex 12
 property float x
 property float y
 property float z

Lines beginning with the word property indicate the type of vertex information. There are 2 types of options, depending on the source of the ply file. The type can be one of char uchar short ushort int uint float double or one of int8 uint8 int16 uint16 int32 uint32 float32 float64 . The faces of an object can be described as follows:

  element face 10
 property list uchar int vertex_indices

The word list shows that the data is presented as a list of values, the first of which is the number of elements in the list (represented by the type 'uchar' in this case), and each occurrence of the list is of the type 'int'. For the usual 'property list ...' polygon representation, the first number for this element is the number of polygon vertices, and the remaining numbers are the indices in the previous vertex list.

At the end of the header is a line indicating its end:

  end_header

In the ASCII version of the format, each vertex and face is described by a single string of numbers separated by spaces. In the binary version of the format, the data is packed next to each other in the byte order set in the workpiece and the type specified in 'property'.

The PLY format was developed in the mid-90s by Greg Turk ^English. and other Stanford graphics lab employees led by Marc Levoy. Its design was inspired by the Wavefront .obj format, but the Obj format is not extensible by arbitrary properties and data groups, for which the keywords 'property' and 'element' were introduced, generalizing the notation of vertices, faces, associated data, etc.

• PLY - Polygon File Format
• Some tools for working with PLY files (C source code)
• rply - ANSI C library for reading and writing PLY files (MIT license)
• libply - C ++ library for reading and writing PLY files (GNU license)
• Another C ++ library for reading and writing PLY files (GPL 3.0 license)
• Repository of 3D models in PLY format