PRC (data format)
PRC ( Product Representation Compact ) is a standardized data format for displaying 3D data . It is particularly popular as a component of 3D PDF , since Adobe Reader can display 3D data in PRC format natively. The main use case is the exchange of CAD models, which should be as uncomplicated as that of PDF documents.
Data model
A generally accessible and exact description of the logical data model and physical data format is contained in the documentation of the Adobe Acrobat SDK .
The data model supports the mapping of product structures, 3D data and markup.
A product structure consists of assemblies and individual parts; they are mapped in the PRC via the entities ASM_ModelFile , ASM_ProductOccurrence and ASM_Part Definition. They are positioned in space using general or Cartesian transformations .
Individual parts contain references to the 3D data ( RI_RepresentationItem ). These can be available both as a tessellated polygon mesh and as an exact Brep geometry.
The Markup area defines annotations ( MKP_AnnotationSet , MKP_AnnotationItem ) and views ( MKP_View ). Annotations provide additional manufacturing-related information, such as dimensions and labels, which are often summarized under the generic term Product Manufacturing Information (PMI).
Views are responsible for controlling the position and visibility of annotations, assemblies and individual parts. This can be used, for example, to display exploded views or sectional views.
Data format
The storage of PRC data is binary. A PRC file begins with the three characters PRC . The serialized data model then follows, divided into one or more file structures , which in turn consist of the parts header , globals , tree , tessellation and geometry . This division makes it possible to implement PRC readers that only handle part of the data model, for example only read tessellated data and ignore the exact geometry.
The serialization of the data model into a file takes place with the aim of minimizing the file size. Various methods are used for this, such as the definition of variable lengths for integers ( bit-by-bit writing ), the use of a lookup table for frequently used floating point numbers and the use of the data compression method Gzip .
PRC data are rarely available as a separate file. Most of the time, the data is embedded as a binary data stream ( COSStream with the name 3DD ) in a 3D PDF file. The Adobe Reader is displayed Version 9 or able to PRC data stream via its built-in, interactive 3D viewer.
standardization
The International Organization for Standardization (ISO) standardized the PRC data format as an industry standard in 2015.
Web links
- Examples of 3D PDF files with embedded PRC ( Memento from March 4, 2016 in the Internet Archive )
Individual evidence
- ^ PRC Format Specification from Adobe
- ↑ PDF specifications at Adobe Systems
- ↑ ISO 14739-1: 2014