Wednesday, August 3, 2011

Understand the Effect of Format Changes

You can convert a drawing to a format compatible with previous versions of the AutoCAD/LT by using AECTOACAD command (or in LT2012 DWGCONVERT command). This process however creates a drawing with information specific to the current release stripped out or converted to another object type. When the drawing is converted, a log file lists changed or lost information. These commands also strip any information created by vertical versions of AutoCAD (such as AutoCAD Architecture or Civil 3D) to regular AutoCAD entities, stripping any roundtripping of the new file back to the original application.

Since converting a drawing to an earlier release format may cause some data loss, you should considerassigning a unique file name (or by adding the year-version number to the current file name) to avoid overwriting the current drawing file. The following items are affected:

  • Visual Fidelity of Dimension. The following dimension enhancements do not lose visual fidelity in previous releases if they are not edited: Dimension breaks, Jogged linear dimensions, Inspection dimensions, Angular dimensions that are dimensioned using the quadrant option, and Arc extension lines for radial and diameter dimensions
  • Visual Fidelity for Annotative Objects and Annotative Blocks can be set in OPTIONS command: ideal if you want to allow the lower versions of AutoCAD to see each of your annotative block representations as individual objects on individual layers.
  • Layer Property Overrides are not visible in LT versions lower than LT2008, but remain intact if returned to the later LT version.
  • Multiline Text Objects: Some of the paragraph spacing and paragraph line spacing options are not supported when an AutoCAD/LT 2008 or higher multiline text object is opened in AutoCAD/LT 2007 and earlier releases.
  • Tables and Data Extraction: Editing AutoCAD 2008 tables in previous releases removes AutoCAD/LT 2008 table formatting. Also, AutoCAD/LT 2008 table cells with long block and text strings may extend outside of cell borders when opened in previous releases.
  • AutoCAD Architecture (ACA) Custom Objects are converted to plain AutoCAD/LT object types.

Additional limitations of Saving to Earlier Versions:
Converting a drawing to AutoCAD 2007 format is subject to the following limitations:

  • DGN underlays do not display in releases prior to AutoCAD/LT 2008.
  • Multileaders display as proxy objects in releases prior to AutoCAD/LT 2008.
Converting a drawing to AutoCAD 2004 format is subject to the following limitations:
  • Dynamic block geometry can be redefined independent of the block’s dynamic elements, and the geometry in the block reference is not updated when the drawing is opened in a product based on AutoCAD 2007 or later.
Converting a drawing to AutoCAD 2000 format is subject to the following limitations:
  • File size can increase.
  • Encryption and digital signatures are not preserved.
Converting a drawing in AutoCAD Release 14/AutoCAD LT 98/AutoCAD LT 97 format is subject to the following limitations:
  • Hyperlinks are converted to AutoCAD Release 14 attached URLs.
  • Database links and freestanding labels are converted to AutoCAD Release 14 links and displayable attributes.
  • Database attached labels are converted to multiline text and leader objects, and their link information is not available. Attached labels are restored if you open the drawing in AutoCAD 2000 or later.
  • Arc length and jogged dimension objects might not retain their original color in AutoCAD Release 14.

Conversion or not, the free DWGTRUEVIEW free viewer from Autodesk has it's own limitations that are not related to any of the above:

  • Dynamic Constraints: Dynamic contraints created in AutoCAD 2010-based products do not display in DWG TrueView.
  • DWGTrueView does not convert of pen-width settings to lineweights when exporting to R14DWG format.