PLY - Polygon File Format
PLY (Polygon File Format, also known as the Stanford Triangle Format) is a format for storing graphical objects that are described as a collection of polygons.
The PLY format has two sub-formats: an ASCII representation for easily getting started, and a binary version for compact storage and for rapid saving and loading.
PLY files are sometimes used for storing point clouds, however the format is designed to describes a mesh object as a collection of vertices, faces and other elements, along with properties such as color and normal direction that can be attached to these elements.
Sources
Columns
Columns (properties) that might be stored include: color, surface normals, texture coordinates, transparency, range data confidence, and different properties for the front and back of a polygon.
Detailed File Structure
This is the structure of a typical PLY file:
- Header
- Vertex List
- Face List
- (lists of other elements)
The header is a series of carriage-return terminated lines of text that describe the remainder of the file. The ASCII header contains lines such as
- a description of each element type, including the element's name (e.g. "edge"),
- how many such elements are in the object, and a list of the various properties associated with the element.
- whether the file is binary or ASCII.
Following the header is one list of elements for each element type, presented in the order described in the header.
Example File
Below is the complete ASCII description for a cube. The header of a binary version of the same object would differ only in substituting the word "binary_little_endian" or "binary_big_endian" for the word "ascii". The comments in brackets are NOT part of the file, they are annotations to this example. Comments in files are ordinary keyword-identified lines that begin with the word "comment".
ply
format ascii 1.0 { ascii/binary, format version number }
comment made by Greg Turk { comments keyword specified, like all lines }
comment this file is a cube
element vertex 8 { define "vertex" element, 8 of them in file }
property float x { vertex contains float "x" coordinate }
property float y { y coordinate is also a vertex property }
property float z { z coordinate, too }
element face 6 { there are 6 "face" elements in the file }
property list uchar int vertex_index { "vertex_indices" is a list of ints }
end_header { delimits the end of the header }
0 0 0 { start of vertex list }
0 0 1
0 1 1
0 1 0
1 0 0
1 0 1
1 1 1
1 1 0
4 0 1 2 3 { start of face list }
4 7 6 5 4
4 0 4 5 1
4 1 5 6 2
4 2 6 7 3
4 3 7 4 0