If you work primarily in model space, it is recommended 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 visual fidelity should be turned on (SAVEFIDELITY set to 1).
Annotative objects may have multiple . When visual fidelity is on, annotative objects are decomposed and scale representations are saved (in an ) to separate layers. These layers are named based on their original layer and appended with a number. If you explode the block in AutoCAD 2007 (or earlier releases), and then open the drawing in AutoCAD 2008 (or later releases), 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 with a drawing created in AutoCAD 2008 (and later releases) in AutoCAD 2007 (and earlier releases).
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 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 than in AutoCAD 2008 and later releases.
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 AutoCAD 2007 (and earlier releases).
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 release, 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 release, the override settings are not retained and are not available when the drawing is opened in AutoCAD 2008.
If you open an AutoCAD 2008 drawing in a previous release, property overrides may display in a thumbnail image. When the drawing is saved with a layout tab, and then opened in the previous release, those property overrides do not display.
Editing AutoCAD 2008 tables in previous releases removes AutoCAD 2008 table formatting. Also, AutoCAD 2008 table cells with long block and text strings may extend outside of cell borders when opened in previous releases.
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.
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.
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.