Visual Fidelity for Annotative Objects in Previous Versions

You can specify that “annotative” objects maintain visual fidelity when they are
viewed in earlier versions of the product, with the SAVEFIDELITY system variable.

If you work primarily in model space, we recommend that you turn off visual fidelity
(set SAVEFIDELITY to 0). However, if you need to exchange drawings with other users,
and layout fidelity is most important, then turn on visual fidelity (set SAVEFIDELITY
to 1).

Annotative objects may have multiple scale representation. When visual fidelity is
on, annotative objects are decomposed and scale representations are saved (in an anonymous
block) to separate layers. These layers are named based on their original layer and
appended with a number. If you explode the block in an earlier version, and then open
the drawing in the current version, each scale representation becomes a separate annotative
object, each with one annotation scale. It is recommended that you do not edit or
create objects on these layers when working on such a drawing with an earlier version.

When visual fidelity for annotative objects is not selected, a single model space
representation is displayed on the Model tab. Depending on the setting of the ANNOALLVISIBLE
system variable, more annotation objects may be displayed on the Model tab, and more
objects may be displayed in paper space viewports at different sizes when viewed in
an earlier version.

Annotative Object Properties in Previous Versions

In an AutoCAD 2008 drawing, when an annotative block does not have its paper orientation
set to match the layout, and the block contains multiline attributes that are based
on a text style that is not set to match the orientation of the layout, the attributes
may shift positions if you open this drawing in an earlier version.

Layer Property Overrides in Previous Versions

When you open an AutoCAD 2008 drawing containing layer property overrides, overrides
are not visible. The property override settings are retained when the drawing is saved
in a previous version, and are visible again when the drawing is opened in AutoCAD
2008.

If a viewport containing layer property overrides is deleted when the drawing is
opened in a previous version, the override settings are not retained and are not available
when the drawing is opened in the current version.

When the VISRETAIN system variable is set to 0 when the drawing is opened in a previous
version, xref layers containing viewport property overrides are not retained.

If you open an AutoCAD 2008 drawing in a previous version, property overrides may
display in a thumbnail image. When the drawing is saved with a layout tab, and then
opened in the previous version, those property overrides do not display.

DGN Underlays in Previous Versions

DGN underlays do not display in versions prior to AutoCAD 2008.

Dimension Enhancements in Previous Versions

AutoCAD 2008 dimension enhancements are lost when they are edited in earlier versions.
If you don’t change these dimensions, they are restored when you open the drawing
in AutoCAD 2008.

The following dimension enhancements do not lose visual fidelity in previous versions
if they are not edited:

• Dimension breaks
• Jogged linear dimensions
• Inspection dimensions
• Angular dimensions that are dimensioned using the quadrant option
• Arc extension lines for radial and diameter dimensions

Multileader Objects in Previous Versions

Multileaders display as proxy objects in versions prior to AutoCAD 2008 and related
products. The PROXYSHOW system variable controls the display of proxy objects in a
drawing.

MTEXT Paragraph and Paragraph Line Spacing in Previous Versions

Some of the new paragraph spacing and paragraph line spacing options are not supported
when an AutoCAD 2008 mtext object is opened in earlier versions.

The following mtext formatting features have no visual fidelity in previous versions:

• Paragraphs with justified alignment
• Paragraphs with distributed alignment
• Fields that wrap across columns
• Fields that wrap across lines that have new paragraph alignments
• Paragraphs with non-default alignments in mtext without left object-level justification

The following mtext formatting features have some visual fidelity in previous versions (when it’s possible to add white spaces or replace
text with white spaces):

• Paragraphs with non-default alignments (other than justified or distributed) in mtext
  that has left object-level justification
• Paragraphs with tabs using new tab alignments (center, right, or decimal alignment
  applied)
• Paragraphs with new line spacing that can be “approximated” with “tall” spaces

Mtext with new formatting that is edited and saved in previous versions loses the
new formatting when re-opened in AutoCAD 2008.

Tables in Previous Versions

Editing AutoCAD 2008 tables in previous versions removes AutoCAD 2008 table formatting.
Also, table cells with long block and text strings may extend outside of cell borders
when opened in previous versions.

Data Extraction Tables in Previous Versions

For tables that were created with the Data Extraction wizard in AutoCAD 2008, you
can’t edit or update the extracted data in previous versions.

Materials in Previous Versions

AutoCAD 2008 introduces new procedural maps for materials and luminance. Drawings
created earlier than AutoCAD 2007 that contain materials need to be converted. AutoCAD
2008 provides a system variable, 3DCONVERSIONMODE, that is set to automatically convert
old materials to the AutoCAD 2008 format. However, there are some fidelity issues
when saving back to previous versions of AutoCAD.

• Procedural maps Checker, Noise, Speckle, Tiles, and Waves are not available in AutoCAD
  2007 (and previous versions.) They do not appear when an AutoCAd 2008 drawing is opened
  in AutoCAD 2007. Marble and Wood are available but the material mayshow some variation.

• The behavior of the Opacity map channel under the Realistic material type has been
  corrected in AutoCAD 2008. In AutoCAD 2008, the Opacity map channel behaves like a
  transparency map, where white is transparent and black is opaque (this was how it
  behaved prior to AutoCAD 2007). In AutoCAD 2007, white represented opaque areas and
  black represented transparent areas.
• The spherical map rotation is different in AutoCAD 2008. When you open a drawing prior
  to AutoCAD 2008 AutoCAD 2008, the seam for the map is towards the +Y axis. In AutoCAD
  2008, it is towards the +X axis.

Lighting in Previous Versions

AutoCAD 2008 provides two options for lighting: standard (generic) lighting and photometric
lighting. Previous versions offered only standard (generic) lighting. There is no
explicit conversion required for lights from AutoCAD 2007 to AutoCAD 2008. Drawings
from AutoCAD 2007 open by default in AutoCAD 2008 in the standard (generic) lighting
workflow. The additional photometric properties available in AutoCAD 2008 are available
as soon as the photometric lighting workflow is enabled in the drawing.

There is a conversion process required for drawings with lighting prior to AutoCAD
2007. You can use a system variable, 3DVCONVERSTIONMODE, to automatically convert
drawings with lighting from previous versions to the AutoCAD 2007 and AutoCAD 2008
lighting format. 3DCONVERSIONMODE has three settings. If set to 0, no conversion takes
place. If set to 1, the default value, the conversion takes place automatically. If
set to 2, then you are prompted when lights need to be converted and will have the
option to convert or not to convert.

Other lighting fidelity issues include

• Lights in blocks. Lights in blocks created in AutoCAD 2008 do not always display in AutoCAD 2007.
• Texture illumination. In versions prior to AutoCAD 2008, you can’t add lighting to textures. In AutoCAD
  2008, you can.
• Ground Shadows. The intensity of ground shadows in AutoCAD 2008 depends on the brightness of the
  light and angle of incidence.

Multiple-Language Support in Previous Versions

Drawing properties in AutoCAD 2008 are saved with Unicode characters. For instance,
if you save the latest format drawing containing multiple language drawing properties
to a 2004-format drawing, the drawing properties are converted to the native characters
of the current Windows language. If text cannot be converted to the native characters,
it is saved to CIF codes (U+nnnn) or MIF codes (M+nxxxx).

When saving the latest format drawing to a 2004-format drawing, any new symbol or
dictionary names (for example, layout name, text style name, dimension style name)
created in AutoCAD 2008 are saved in the language that was used when the symbol names
were created.

In order to view and edit drawings with characters that are not included in the languages
specified for your operating system, make sure supplemental language support is installed
in your computer operating system. You can specify the language in the Regional and
Language Options dialog box, available from the Windows Control Panel. (You may be
able to view text that uses SHX fonts without specifying extra language support.)

Text styles for Asian languages that use SHX and Big Font can support characters only
from the same code page. For example, text styles that use a Japanese Big Font cannot
support German or Korean characters. (English characters, which are part of every
code page, are supported.) Multiple-language support for non-Asian languages is supported
for text styles that use SHX fonts with Big Fonts disabled. (The SHX font must define
the required characters.)

Multiple-language support does not exist in some earlier versions of AutoCAD. For
example, when you save a file to AutoCAD 2000 format, the contents of multiple-language
multiline text may be corrupted. This problem is more likely to happen when you open
and save a drawing on an operating system with a system language setting that differs
from the system in which the drawing was last saved.