What you Should Know about IGES Utilities

What IGES Utilities Can Do
If IGES utilities are available, they can help identify and repair the causes of many problems. An IGES analysis or checker utility applied during interoperability testing can help find problems with syntax and file structure such as:

1. Data extending past field boundaries, such as parameter data written past column 64 in the parameter data section.
2. Mis-defined entity form numbers, such as a 3D entity being written as a 2D form.
3. Problems with associativities and properties, such as incorrectly applied pointers.
4. Data values that are out of range, such as zero length lines or negative text heights.

Pinpointing Pre or Postprocessor Errors
When an IGES analysis or checking utility is available, it may be possible to determine which of the IGES processors is responsible for causing certain errors. For example, if a post-processor reports problems with an entity that was also reported by an analysis utility, then the pre-processor may be suspect. If however, there are problems with a transferred file that passed the analysis without incident, the post-processor may be suspect.

IGES Viewing Utilities
If an IGES viewing utility is available, it too can be used to help pinpoint translation problems. It can highlight the same problems that were visible on plots, as well as some that were not visible. Deductive reasoning can help pinpoint the causes. IGES viewers can find:

1. Improperly placed clipping planes, drawing entities or view entities. A viewer will explicitly identify these problems rather than require you to guess at problems that are implied by how plots look.
2. Entities that have been changed or converted to other entity types in such a way as their function has been changed, such as b-splines being converted to polylines.
3. Data that has been lost through degeneration of entities, such as circles broken into straight line segments or dimensions exploded to text and geometry.

Product Capability
Any IGES utility will utilize the vendor's own methods for interpreting IGES files. This is what sets the vendors apart, their abilities to perform mathematical approximations (like when mapping higher order b-splines to lower orders), their ability to read and write the newest (or oldest) versions of IGES, and the robustness of their ability to handle and report problems with IGES files.

Product Reliability
Perhaps the most important characteristic of IGES utilities and services is the extent to which you trust the product or vendor. If you want to use a product as a debugging tool, you will be relying on the product to properly identify the problems and to find all errors present in an IGES file. To put it another way, you should believe that the product is doing what you intend it to do.

Human Understanding
Do not expect any IGES utility to remove the requirement of human understanding of the IGES standard or the physical file layout requirements. Many IGES utilities assume that you are somewhat familiar with IGES already. However, many offer mechanisms to make it easier to understand the data in an IGES file by identifying fields and explaining the true meanings of cryptic values.

Source:
Hap Stokes, Engineering Consultant