1. The Development of Support for PMI in STEP AP203E2 and AP214
Tony Ranger Technical Director Theorem Solutions Ltd.

2. Theorem Solutions : Interoperability Experts

3. Theorem Solutions : Major Partnerships
Siemens PLM Software
UG NX, JT, NX I-DEAS, Parasolid
Dassault Systemes
Catia V5, Enovia, Delmia
Parametric Technologies
ProE Wildfire, ProductView

4. Theorem involvement with STEP
1993 : STEP development for CADDS 5
PDES Inc. AeroSTEP pilot
Boeing, Rolls Royce, Pratt & Whitney, General Electric
AP203 Class 6 Brep Solids
1993-Present
Members of PDES Inc. and ProSTEP
Participants in CAX-IF
(previously STEPNet & ProSTEP Roundtable)
Member of AP203 Certification Board
Participated in ISO SC4 meetings

5. Production STEP Processors
CADDS 5
UG NX
Parasolid
CATIA V4
SC03

6. STEP and 3D PMI Representation Data
The semantic information in an intelligent form
machine readable
Presentation Data
The display definition of the information
human readable

7. Example of Simple Dimension
What you see here is the presentation

8. Representation and Presentation Data
Representation Data
Diameter Dimension
Value of dimension 1.0
Plus Minus Tolerance for diameter 0.003
Presentation Data
3 Text Strings : “<0>” “1.000” “<$t>.003” (UG NX)
“\S\X” “1.000” “\S\1.003” (STEP)
Text font, width, height, character and line spacing
WCS Definition
Position in WCS
Leader line, dimension line, arrowhead symbol
definition and placement

9. Sub Classifications of Presentation Data
There are many ways of defining the presentation data.
The CAX-IF has defined 3 ways for which recommended practices will be produced.
Polyline Presentation
Minimal Semantic Presentation
Full Semantic Presentation

10. Polyline Presentation Data
Definition of presentation data
(my understanding)
All display graphics defined as polyline or circular arc 3D geometry.

11. Minimal Semantic Presentation Data
Definition of presentation data
(my understanding)
The minimum amount of data which, together with the representation data, allows the target system to create the PMI display information in its natural (native) form.

12. Full Semantic Presentation Data
Definition of presentation data
(my understanding)
A full set of semantic presentation data (text, curves, symbols) such that the PMI display information can be created in the target system.

13. Some Advantages / Disadvantages Polyline Presentation
Polyline is very simple WYSIWYG
No intelligence
Difficult to validate content

14. Some Advantages / Disadvantages Minimal Semantic Presentation
Minimal Semantics is not WYSIWYG
Full intelligence – translated PMI object behaves as native object because it is a native object

15. Some Advantages / Disadvantages Full Semantic Presentation
Full Semantics is almost WYSIWYG
Limited intelligence – because it is not created as native semantic PMI object. In UG NX may create “Assorted Parts Dimension”
Can be linked with intelligent objects – dependent on system API functionality.

16. Text Font IGES translation for drawings – the light box test.
Different systems have different font tables.
Even if fonts have the same name they may not satisfy the window text.
STEP provides for the AP to define supported fonts.

17. STEP Document Structure
Resource Parts
e.g. Part 42
Product data representation and exchange: Integrated generic resource: Geometric and topological representation
AICs
e.g. Part 520
Application interpreted construct: Associative draughting elements
APs
e.g. Part 202
Application protocol: Associative draughting

18. STEP Entity Definition Context
AICs are based on resource parts and extend them for a specific application discipline. Additional subtypes of entities may be created to specialise the meaning of that entity.
Application Protocols are built from resource parts and AICs. Any recommended practices produced are specifically relevant to APs which support all of the entity definitions, the rules, the valid defined text strings and select types.

19. Text Font IGES translation for drawings – the window test.
Different systems have different font tables.
Even if fonts have the same name they may not satisfy the window text.
STEP provides for the AP to define supported fonts.
AP 214 : ‘ISO font A’ ‘ISO font B’
AP 203 E2 : ‘ISO 3098’
In addition, there is a capability for non-formal support of fonts.
These need to be semi-formalised via recommended practice.

20. ISO 3098 Technical Product Documentation - Lettering

21. ISO Font A

22. Recommended Practice for Text Font
text_literal ->font : font_select;
font_select = SELECT (pre_defined_text_font, externally_defined_text_font);
pre_defined_text_font : SUBTYPE OF (pre_defined_item);
pre_defined_item -> name : label;
Current recommended practice is to always use a subtype of pre_defined_text_font.
draughting_ pre_defined_text_font has rules limiting the content of the name attribute.

23. New Recommended Practices ?
text_literal ->font : either pre_defined_text_font or externally_defined_text_font
pre_defined_text_font -> name : label;
New Recommended Practice could provide for use of pre_defined_text_font with specifically agreed names. E.g. Arial

24. New Recommended Practices ?
text_literal ->font : either pre_defined_text_font or externally_defined_text_font
pre_defined_text_font -> name : label;
New Recommended Practice could provide for use of pre_defined_text_font with specifically agreed names. E.g. Arial
externally_defined_text_font is a subtype of externally_defined_item
source : identifier – for example “UG NX”
Item_id : identifier – for example “blockfont”

25. Recommended Practice for Handling Text
Key property of a text string is the space it takes in the display.

26. Recommended Practice for Handling Text
Key property of a text string is the space it takes in the display.
This is a PMI note providing some information
This is an appended note.

27. Recommended Practice for Handling Text
Key property of a text string is the space it takes in the display.
If the space that the text uses is incorrect, it can cause problems.
This is a PMI note providing some information
This is an appended note.
This is a PMI note providing some information
This is an appended note.

28. Recommended Practice for Handling Text
Key property of a text string is the space it takes in the display.
If the space that the text uses is incorrect, it can cause problems.
This is a PMI note providing some information
This is an appended note.
This is a PMI note providing some information
This is an appended note.
Recommended Practice : use text_literal_with_extent to define text. During post-processing, select text size properties to ensure the text uses the same extents box.

29. Combinations of forms of data within STEP
Representation Data
Useful only for systems which do not require presentation content (e.g. UG NX)
Representation Data and Presentation Data
Minimal or Full Semantic Presentation Data
Presentation Data
Full Semantic or Polyline Presentation Data

30. Associativity
CAD systems can retain full associativity of PMI with the underlying geometry.
STEP supports associativity of PMI with geometry but it is very cumbersome and yet not as detailed as the native CAD data.

31. Linear Dimension
This is a vertical dimension between the end points of 2 parallel lines.

32. Linear Dimension
This is a vertical dimension between the end points of 2 parallel lines.

33. Object Associativity
Within UG NX the associativity information is quite detailed – the UF_DRF_object_assoc_data structure defines which end of the line is referenced or, for arc edges, can point to the centre of the arc or a tangency point on the arc.
Within STEP, the information is much more cumbersome and is not so detailed.

34. STEP Object Associativity

35. Linear Dimension to Centre of Arc
For this, UG NX has associativity flag to identify referred point as the centre of the arc.

36. STEP Object Associativity
Axis_placement

37. Derived Associativity Data
The STEP associativity is defined but it is not as specific as the data held by the native CAD systems.
The STEP post-processors can look for possible relationships – such as tangent point or arc centre point – and can derive the level of information required by the CAD systems but it requires more work.

38. Complex PMI

39. Complex PMI

40. What does it mean to the user?
This applies to 6 holes
Diameter Dimension
Value 3.4
Max limit tolerance plus 0.08
Min limit tolerance
Depth of hole 6
Max limit tolerance on depth 0.5
Min limit tolerance on depth 0.0
Countersink Diameter 4.1
Max limit tolerance on countersink diameter 0.25
Min limit tolerance on countersink diameter 0.
Countersink included angle between 82 and 100 degrees
Screw Thread Definition “M4X0.7 – 6H” has a minimum depth of 4
Position tolerance for hole centre has diameter of 0.25
Projected Tolerance Zone has minimum height of 6
Position related to datums D, E, C (in that order)

41. What does it mean to UG NX
It is a diameter dimension
It has 6 text strings

42. What does it mean to UG NX
It is a diameter dimension
It has 6 text strings

43. What does it mean to UG NX
It is a diameter dimension
It has 6 text strings
It has a value text : “3.4”
It has a prefix text : “6X”
The other 4 texts are appended text
Most interesting is text object with 3 lines
“<#C><0>4.1<T+0.25! 0> X 82<$s>-100<$s>”
“M4X0.7-6H <#D>4 MIN”
“<&70><+><&10><+><0>0.25<P>6<+>D<+>E<+>C<+><&90>”

44. Interpreting the data
For STEP, this needs to be interpreted into a set of representation entities.
dimensional_size
plus_minus_tolerance
position_tolerance
Datums

45. Interpreting the data
For STEP, this needs to be interpreted into a set of representation entities.
dimensional_size
plus_minus_tolerance
position_tolerance
Datums
But these representation entities leave a lot of information which is not defined.

46. Interpreting the data
For STEP, this needs to be interpreted into a set of representation entities.
dimensional_size
plus_minus_tolerance
position_tolerance
Datums
Text Data is required to complete the semantic content. Representation data in itself is incomplete.

47. Full Part PMI
Top View of Part

48. Is it usable?
Complex PMI example

49. Saved View as Work View
User Creates sub-set of full PMI to be visible in view

50. STEP draughting model + camera model
The way that the presentation information is gathered together within a part is using a draughting model.
The geometry is defined within a shape representation. The draughting model references the geometry from the shape representation and can add additional annotation information in a single presentation.
The draughting model can also reference a camera model. The Recommended Practice will state that a draughting model containing a single camera model together with all or a subset of the PMI represents a saved view definition.

51. Draughting model linked to geometry
Extracted from the Polyline Recommended Practice Document

52. LOTAR Polyline Presentation Project
Objective : to create a Recommended Practice document for Polyline Presentation of PMI and to create processors for CATIA V5 and UG NX to demonstrate the capability.
Participants : US & European Aerospace companies, ProSTEP, Dassault Systemes and Theorem Solutions.
Status : RP document close to final draft, software in final testing stages.
Saved Views will be supported in the RP document but not in the initial software.

53. NIST Semantic Presentation Project
Objective : to create a Recommended Practice document for Semantic Presentation of PMI and to create processors for ProE Wildfire and UG NX to demonstrate the capability.
Participants : NIST, PDES, PTC and Theorem Solutions.
Status : RP document under development, software in early development stages.
Saved Views will be supported in the RP document and possibly in the software.

54. Complex PMI example reflected through STEP
Reflected via Polyline Presentation
Original
Reflected via Full Semantic Presentation

55. Thank You Questions?