Skip to content

Latest commit

 

History

History
114 lines (67 loc) · 4.34 KB

README.md

File metadata and controls

114 lines (67 loc) · 4.34 KB
Raw

pCache - point cache file

pcache files contains simple structured data for point cache files. The file format is close to Stanford's PLY and reduces the feature set to the minimum required for storing only point data. Data types are also adjusted to be able to match the requirements of a point cache.

Header

File header is described by a succession of ASCII Lines regardless if data is stored in binary or ASCII. Lines are ended using the UNIX newline character \n

Magic number

The first line of the header is always as following, in lowercase:

pcache

Format identifier

The second line of the header identifies the data format, and the version of the data format.

format data_format version

Data format can be ascii or binary. Binary formats are always Little-Endian. Version information will be detailed in the Changelog.

Examples :

format ascii 1.0

format binary 1.0

Comments

Comments can be added with lines starting with comment, the end of comment is terminated by the newline.

comment This is a really pretty comment.

Element count

A line starting with elements will state the amount of individual elements present in the file.

elements 9122

Properties

Properties describe the data layout present in the file. Every property is described in one line starting with the property . Each property is described with a type and a name such as:

property type name

Types are described in the Type Section of this document.

Names are ASCII strings with the following restrictions:

  • name must start with an alphabetic character. [A-Z , a-z]
  • only allowed special characters are underscore _ and point .
  • Point is assumed to reference a structured data (eg: velocity.x) although this is only a convention.

Header Ending

Header is terminated by the line end_header

Data Structure

Data is stored into an Array of Struct succession of elements in both modes.

ASCII Data

ASCII Data is stored as a succession of ASCII strings for values separated by spaces or UNIX newlines (\n). For readability concerns it is assumed that one element's values are separated by spaces, and elements are separated by newlines. However this convention is totally optional and not mandatory to ensure valid data.

This means that Spaces and newlines have to be treated as the same.

ASCII Data is validated using the following conventions:

  • Range is evaluated depending on the type
  • Negative values use a leading dash (-237)
  • Floating point values uses the dot . as the radix point. Floating point without fractional parts can omit the radix point and the fractional part.

Binary Data

Binary data is stored streamlined as a BLOB with no separators. As an array of struct.

Data Types

Data types can be the following:

Name Type Stride (Bytes)
char 8-bit signed integer value 1
uchar 8-bit unsigned integer value 1
short 16-bit signed integer value 2
ushort 16-bit unsigned integer value 2
int 32-bit signed integer value 4
uint 32-bit unsigned integer value 4
float 32-bit signed floating-point value 4
double 64-bit signed floating-point value 8

Property naming and conventions

Here is a list of suggestion for common naming and conventions for commonly used properties:

Name Type Description
position float, 3 components x,y,z position of the point
velocity float, 3 components x,y,z Velocity
color float/uchar, 4 components r,g,b,a Color (HDR/LDR)
size float (multiple components) x,y,z Size of the point
age float Age of the point
lifetime float Expected Lifetime of the point

ChangeLog

Version 1.0

Initial version