The document discusses various computer-aided design (CAD) standards used for data exchange, including graphics standards like GKS and OpenGL, as well as data exchange standards like IGES, DXF, and STEP. It provides details on the purpose and requirements of each standard, explaining concepts like layers, entities, and file structure. The key standards discussed are IGES for shape data exchange, DXF for CAD file interchange, and STEP for comprehensive product data across the design and manufacturing lifecycle.

1. UNIT - V
J.S.JAVITH SALEEM AP/MECH
AL AMEEN ENGINEERING COLLEGE
ERODE

2. • CAD Standards are a set of guidelines for the way Computer-aided
design (CAD) drawings should appear, to improve productivity and
interchange of CAD documents between different offices and CAD
programs, especially in architecture and engineering.

4. Standards for computer graphics-Need for
graphic standards
• Need for portability of the geometric model among different hardware
platforms.
• Exchange drawing database among software packages.
• Need for exchanging graphic data between different computer system.
• Need for the requirement of graphic data exchange formats and their
details such as IGES ,DXF,STEP.

5. SOME OF GRAPHIC STANDARDS

6. FOUR TYPES OF MODELNG DATA USED IN PRODUT
DESCRIPTION
• Shape data contains information of both geometrical and topographical
information along with surface features.
• Non shape data contains shade images and model global data.
• Design data
• Manufacturing data

7. Requirements for the Exchange
• Shape data: both geometric and topological information, part or form features.
Fonts, color, annotation are considered part of the geometric information.
• Non-shape data: graphics data such as shaded images, and model global data as
measuring units of the database and the resolution of storing the database numerical
values.
• Design data: information that designers generate from geometric models for
analysis purposes. Mass property and finite element mesh data belong to this type of
data.
• Manufacturing data: information as tooling, NC tool paths, tolerancing, process
planning, tool design, and bill of materials (BOM).

8. CLASSIFICATION OF CAD STANDARDS
• Graphics and computing Standards-GKS, OpenGL
• Data Exchange Standards-IGES,DXF,STEP,CALS
• Communication Standards
JAVITH SALEEM AP/MECH

9. Graphics standard
• Focus of this standard is that the application program should be device
independent and should interface to any input device handler and to any
graphics display through a device driver.
• The graphics system is divide into two parts ; Kernel system which is
hardware –independent and the device handler /driver ,which is naturally
hardware dependent.
• Kernel system act as buffer between the application program and the specific
hardware to ensure the independent and portability of the program .

10. Graphics standard

11. Graphics
standards in
graphics
programming

12. Graphics Kernel system
• GKS is basically a set of procedure which can be called by user programs
to carry out certain generalized functions such as arc,circle,ellipse etc.
• It is a standardized system of graphical functions for processing graphical
data to create and process 2D images.
• GSK implementations have been made by many hardware manufactures in
many languages.

13. LAYER MODEL OF GKS

14. Features of GKS
• It is an independent device ,it can work with all types of input and output
devices.
• All text and annotation can be prepared and stored in natural languages.
• Graphic functions are defined for both 2D and 3D
• GKS defines an international coordinate system called normalized device
coordinate system .

15. Classifications of GKS
1. control functions
2. Output attributes
3. Output primitives
4. Segment functions
5. Transformations
6. Input functions
7. Metafile functions
8. Inquiry functions

16. Output primitives & Output attributes
• Circle is a primitives
• Attributes may be color, line width and line types

17. Examples
• POLYLINE
• POLYMARKER
• TEXT
• FILL AREA

18. GKS INQUIRY FUNCTIONS
• Functions are used to find the current status of any variable in GKS.
• It is mainly used to isolate the predefined values of variables if
anything is required.
Example : transformation and clippings

19. GKS INPUT FUNCTIONS
• A set of functionality is defined in the category is known as input
functions.
• The devices which are connected in a graphic system are to act an
input element such as tablets, mouse, keyboard and joystick.

20. Metafile functions
• Files to store, retrieve and display the graphical data to handle device
independent formats.

21. PHIGS

23. Data Exchange Standards

24. IGES (Initial Graphics Exchange
Specification)
• First developed by National Institute of Standards and Technology (NIST)
in 1980.
• Then adopted by the American National Standards Institute (ANSI) in the
same year. exchanges primarily shape (both geometric and topological) and
non-shape data, which is referred as CAD-to-CAD exchange.

25. IGES (Initial Graphics Exchange
Specification)
• codes a superset of common entities of all CAD/CAM systems to
facilitate the translation between various systems.

26. Development of IGES

27. IGES (Initial
Graphics Exchange
Specification) –
Geometry Entities

28. IGES (Initial Graphics Exchange
Specification) –Annotation Entities

29. IGES (Initial Graphics Exchange
Specification) –Structure Entities

30. IGES (Initial Graphics Exchange
Specification) –File structure

31. Flag section
• Used only with the compressed ASCII and binary format .
• IGES data in a file can be represented in two formats :ASCII and binary
• ASCII - American Standard Code for Information Interchange.
• ASCII format comprises two types : fixed 80-character record length and
compressed format .
• Compressed format contains compressed file by eliminating spaces from the
records.

32. Start section
• Provides a human –readable description of the file, such as
the sending system that generated the original data, the
pre-processor ,and the product being described.

33. Global section
• Included information telling the pre-processor and
information needed by the post –processor to interpret the
files.
• Some item specified example : the data and time of the file
generation .

34. Directory Entry section
• Is a list of all the entities together with certain of their attributes.
• All product definition data are expressed as a list of predefined entities (geometry
and annotation entitles ) .
• Entry each entity occupies two 80 –character records that are divide into a total of
twenty 8-character fields .
• First and the eleventh field contains entity type number .
• Second field contains pointer to the Parameter data entry for the entity in the
parameter data section.
• Remain entity will contain (line fonts ,layer number, transformation matrix ).

35. Parameter data section
• Section contains the actual data defining each entity listed in the directory entry
section .
• Example: straight line entity is defined by the 6 coordinates its two end points .
• Each entity always has two records in the directory entry section and number of
records need for each entity in the parameter data section.
• Parameter data is placed in free format of columns 1 through 64.
• Column 65 left blank.
• Columns 66 to 72 on all parameter data records contain the entity pointer
specified in the first record of the entity in the data entry section.

36. Terminate data section
• Section contains a single record which specifies the number of
records in each of the four preceding sections for checking purpose .

39. DRAWING INTERCHANGE FORMAT (DXF)
• DXF into file formats that could be read and used by other CAD/CAM/CAE
sfiles were originally developed to give user flexibility in managing data and
translating AutoCAD drawings ystems.
• DXF standard of interchanging CAD drawing files for almost all
CAD/CAM/CAE systems .
• In fact, almost every newly introduced CAD/CAM/CAE sytem tends to provide
translators to and form the DXF file.

40. DXF file is an ASCII test file and consist of five sections
• Header- describes the AutoCAD drawing environment that existed when the DXF file was
created.
• Table-contains information about line types, layers, text styles, and views that have been
defined in the drawing.
• Block-contains a list of graphic entities that are defined as a group.
• Entity –immediately follows the block section, and serves as the main part of the DXF
file, with all entities of the drawing described in it.
• Terminate-indicates the end of the file.

41. Limitations of IGES and DXF
• IGES and DXF files were developed to exchange product definition
data instead of product data. By product data we mean the data
relevant to entire life cycle of a product (eg: design ,manufacturing,
quality assurance ,testing and support).

42. PDES (Product Data Exchange Standard)
(then Product Data Exchange Using STEP)
• STEP (Standard for the Exchange of Product model data) is a new
International Standard (ISO 10303) for representing and exchanging
product model information.
• Support any industrial application such as mechanical, electric, plant
design, and architecture and engineering construction.
• To include all four types of data which is relevant to the entire life-
cycle of a product: design, analysis, manufacturing, quality assurance,
testing, support, etc.

43. • PDES is a much more comprehensive and complex standard than IGES
or any other predecessors
• The user interface is not as simple as “put IGES” and “get IGES.”

44. MECHANICAL
PRODUCTS
ELECTRICAL
PRODUCTS
AEC
PRODUCTS
APPLICATION N
GENERIC ENTITIES
APPLICATION –SPECIFIC
ENTITIES
FILE FORMAT AND DATA STRUCTURE
STEPARCHITECTURE
Application
layer
Logical
layer
Physical
layer

45. Three layers of STEP
• Application layer –consist of information of various application areas.
• Logical layer-provide a consistent , computer-independent description of
the data constructs that contain information to be exchanged.
• Physical layer –deals with the data structures and data format for exchange
file itself.
• EXPRESS is a formal data specification language used to specify the
representation of product information.

46. Standard for the Exchange of Product model
data
• The goal was to define a standard to cover all aspects of a product (i.e.
geometry, topology, tolerances, materials, etc.), during its lifetime.
• Fundamental difference in IGES and STEP .
• The central unit of data exchange in the IGES model is the entity.
• The central unit of data exchange in the STEP model is the application,
which contains various types of entities.
• Data is exchanged between systems it is done in terms of application units.

48. Continuous acquisition and life –cycle support (CALS).
• It was developed by US department of defense.
• It prescribes the formats for storage and exchange of technical data.
• Focuses mainly technical publications
Important CALS standards
1.Standard generalized markup language (SGML) is an important standard
.developed ibn 1960s IBM . It has the document description language.
2.Computer graphics metafile (CGM) is next important standard .developed in 1986
it is used for the vector file format for illustrations and drawings.

49. Continuous acquisition and life –cycle support
(CALS)
• CALS is an attempt to integrate text, graphics and image data into standard
document architecture.
• All technical publications for the federal government must conform to the
CALS standard.
• CALS has also come into wide use in the commercial computer industry
such as in CAD/CAM applications and in the aerospace industry which
owes a large part of its business to government and military contracts.

50. Continuous acquisition and life –cycle support (CALS)
• Two types of CALS raster formats as defined by MIL-STD-28002A.
• TYPE I –raster data files contain single monochrome image
compressed using CCITT encoding algorithm .
• TYPE II – image file contain one or two monochrome images which
are also stored using CCITT encoding algorithm.

51. Continuous acquisition and life –cycle support (CALS)
Type I file format consist of the following
I. Header
II. Image data
Type II file format looks similar to the format given below.
Header
Document profile
Presentation styles
Document layout
Root layout

52. Layout object page 1
Tile index
Image data
Layout object page 1
Tile index
Image data
Layout object page 1
Tile index
Image data

53. Continuous acquisition and life –cycle support (CALS)
I. File details
II. Header record data block
III. Image record identifiers
IV. SourceDocId
V. DestDocId
VI. Text File ID
I. FiguerID
II. SourceGraph
III. Docclass
IV. Raser type
V. Orientation
VI. Pelcount
VII.Density

54. Open GL –image exchange using Open GL

55. Open GL –image exchange using Open GL

56. What's wrong with using IGES files?
• Technically there's nothing wrong with using the IGES format, however, IGES files tend to
be surface models, and often get translated with gaps between the surfaces, missing faces
and in some instances surfaces with faces in the wrong orientation. While there is is an
IGES standard for solids (IGES-MSBO), it is not often used.
• When a user creates an IGES file, they are translating their native CAD file into the IGES
format. When this file is shared, it is imported into the next CAD package and is translated
again. File translations, could potentially bring in inaccuracies in the geometry.
• The benefit of using the Native CAD file, is that it only requires 1 translation, which is
theoretically more accurate.

57. Why is STEP better than IGES?
• STEP is newer technology, where IGES which is older 1990's technology,
that has not been updated in over 20 years. STEP files tend to be solid
models, where IGES files are more often surface models, which could
have gaps and missing faces.
• STEP is a mature file format, it has been available for over 20 years with
continual development and wide adoption between CAD vendors.
• STEP is widely used, and is even used in the construction industry, the
IFC file format is a version of STEP.