DWG Compatibility in MicroStation® V8

MicroStation V8 "seamless DWG" is good, but not good enough

Issues Investigated

• Visual Fidelity• Performance• Model-Based Design Information• Precision for Shared Data• File “Save As” Sizes

Visual Fidelity

Viewed in AutoCAD

2002

Viewed in MicroStation

V8

Significant visual fidelity differencesSignificant visual fidelity differences

Difference in viewing an AutoCAD sample file

– A common AutoCAD file with basic entities such as lines, arcs, text, and dimensions

Visual FidelityTesting for visual fidelity – Using a widely available test file -Budweiser.dwg – Used for testing the ability of software products to read DWG files – “Pass” criteria is simply that the right and left blocks in each

column must be identical upon opening in the CAD application that is being tested

– Bentley MicroStation V8 failed 7 of the 18 tests

1 of the failed tests

Performance

– For small files (under 1Mb)

– AutoCAD 2002 sample file containing common 2D entities.

Initial Open TimeAutoCAD 2002 3 secondsMicroStation V8 11 seconds

- 3x slower -

– For larger files– 12Mb DWG containing lines,

arcs, polylines, and text representing city property lines

Initial Open TimeAutoCAD 2002 7 secondsMicroStation V8 52 seconds

- 7x slower -

Comparing drawing file open times

Model-Based Design Information

• The display fidelity of model-based design information is critical for users who need to exchange drawings

• Inaccurate proxy graphics support in MicroStation V8, makes certain drawing data created by customers using Autodesk applications unusable in MicroStation V8

• This example shows that with V8 many objects and details are missing such as furniture, windows, landscaping, room tags and 2D objects

Viewed in AutoCAD 2002

Viewed in MicroStation

V8

Precision For Shared DataComparing DXF export of a sample file– Sample drawing exported to an AutoCAD 2000 DXF format file

using AutoCAD 2002 and MicroStation V8– Both exports were performed using the default DXF settings

V8 issues:• Rounding of

numerical values• Data transfer to

other sections of the file

• Missing informationComparison of the two DXF files

File “Save As” Sizes

Comparing size of files with no edited changes– Collection of drawings opened in MicroStation V8, saved as

DGN and then “saved” as DWG.

All sizes in MB

AutoCAD DWG MicroStation V8 DWG

0.334 0.349 +4.5%

5.914 7.144 +21%

16.217 17.126 +5.6%

0.71 0.734 +3.4%

12.038 12.381 +3%

1.198 1.202 +.3%

0.602 0.610 +1.3%

File Size Files Size DeltaFile Size

Key Questions to Ask

• What about obvious visual or plotted differences, are you sure you found them all?

• What are your support costs when data is missing or corrupt?

• How identical are two DWG files that look similar when viewed or plotted but are different in size?

• What issues do you encounter with incorrect data?

• Your design data is your intellectual property, your competitive advantage, your company’s value-- are you willing to risk it?

Conclusions• Bentley’s public claim of “seamless DWG” is relative• Bentley, like many other companies, provides basic

support for common geometry − lines, arcs and circles– Even commonly used design entities, such as SHX fonts,

text styles, linetypes, geometric tolerances and dimension display cause problems

– Bentley’s V8 does not provide any support for editing custom objects created by Autodesk applications such as Autodesk® Architectural Desktop

• Data integrity and visual DWG fidelity problems do exist in MicroStation V8

• Because MicroStation V8 is not completely DWG compatible, the question becomes “what percent of uncertainty in drawing fidelity are you willing to risk?”