Initial Graphics Exchange Specification

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Logo IGES National Institute of Standards and Technology

The Initial Graphics Exchange Specification ( IGES ) defines a neutral, manufacturer-independent data format that is used for the digital exchange of information between computer-aided design programs (CAD). The application ranges from traditional, two-dimensional drawings to three-dimensional models for simulations or manufacturing.

The data is stored in individual units, the so-called entities . These can be arranged in any hierarchy . The primitives of a drawing or a model (such as lines, curves, surfaces) are represented by different entity types. Since the IGES specification version 5, bodies are also provided. That means, a closed surface association also has the information "inside" and "outside".

According to the specification, as with STEP, the information can be stored text-based ( ASCII ) as well as binary . However, the latter format is no longer officially supported. This means that the memory required for an IGES file can easily be several megabytes . The generally accepted file extension for IGES files is .igs.

history

IGES was developed by the US Product Data Association , an industry interest group.

The current version 5.3 became the standard of the ANSI in 1996 . The development activities of the IGES / PDES organization (IPO) resulted in version 6, which was renamed version 5x and published until 2006.

German automotive industry

The Association of the Automotive Industry has with the aim of easier implementation defines various subsets of IGES standards and published together with other requirements under the name VDA-IS:

Dimensioning Rational B-spline
B2 : + levels, drawings with views, ... AF2 : + free-form curves and surfaces (rational form), ...
B1 : Texts, arrows, various dimensions, ... AF1 : Free-form curves and surfaces (polynomial form), ...
geometry
G3 : + Simple surfaces, parametric spline surfaces, ...
G2 : + other data
G1 : curves, circles, lines, points, ...

In the meantime, most of the CAD / CAM and FEM systems used in the vehicle industry have implemented the IGES interfaces with the full range of functions. This is why VDA-IS has lost its original meaning for data exchange.

File format

An IGES file has 80 characters per line. The document consists of several sections. The last number is a consecutive number. The counting is started again with each section.

It starts with the S Section (Start Section). In principle, everything important can be entered there. But it can also remain empty.

Then comes the G Section (Global Section). Here is some information about the file name, storage date and storage location.

This is followed by the D Section (Directory Entry Section) here the individual elements are listed from which the model is built. It also contains information about the line or area color and references to the next section.

This section is called the P Section (Parameter Data Section). It contains information about the exact structure of the element for each element mentioned in the D Section.

The end of the document is the T Section (Terminate Section). The number of lines in each individual section is listed here. Normally this section is only one line long.

This file is an exemplary IGES file. The individual sections can be easily identified in this. 

                                                                        S      1
1H,,1H;,4HSLOT,37H$1$DUA2:[IGESLIB.BDRAFT.B2I]SLOT.IGS;,                G      1
17HBravo3 BravoDRAFT,31HBravo3->IGES V3.002 (02-Oct-87),32,38,6,38,15,  G      2
4HSLOT,1.,1,4HINCH,8,0.08,13H871006.192927,1.E-06,6.,                   G      3
31HD. A. Harrod, Tel. 313/995-6333,24HAPPLICON - Ann Arbor, MI,4,0;     G      4
     116       1       0       1       0       0       0       0       1D      1
     116       1       5       1       0                               0D      2
     116       2       0       1       0       0       0       0       1D      3
     116       1       5       1       0                               0D      4
     100       3       0       1       0       0       0       0       1D      5
     100       1       2       1       0                               0D      6
     100       4       0       1       0       0       0       0       1D      7
     100       1       2       1       0                               0D      8
     110       5       0       1       0       0       0       0       1D      9
     110       1       3       1       0                               0D     10
     110       6       0       1       0       0       0       0       1D     11
     110       1       3       1       0                               0D     12
116,0.,0.,0.,0,0,0;                                                    1P      1
116,5.,0.,0.,0,0,0;                                                    3P      2
100,0.,0.,0.,0.,1.,0.,-1.,0,0;                                         5P      3
100,0.,5.,0.,5.,-1.,5.,1.,0,0;                                         7P      4
110,0.,-1.,0.,5.,-1.,0.,0,0;                                           9P      5
110,0.,1.,0.,5.,1.,0.,0,0;                                            11P      6
S      1G      4D     12P      6                                        T      1

See also

Individual evidence

  1. ↑ CAD: Different formats for different tasks. Retrieved November 13, 2019 .