The 3D_Fields BRConfig.sys specification applies to pre 4.0 versions to add a "3d" appearance to the graphical console.
The 3D FIELDS parameter UNDR ON ignores all other attributes for underlined fields. BR used either the N (normal) attribute or R (reverse) attribute and ORed the other attributes specified (H, B, and U), unless UNDR ON is specified and U is present, in which case it uses the U value exclusively. This provides greater control over the color scheme with 3D FIELDS active. You could then use H for other purposes without affecting UH processing.
When 3D fields are enabled, the screen requires more vertical space than it otherwise would. Therefore, the BR window takes on a rectangular appearance, and doesn't look as good in full screen mode as it does as a window.
To activate this feature, specify 3D FIELDS ON in your BRconfig.SYS file and also specify SCREEN U 0170 only. (Or specify SCREEN U 0170,N 38 to add some flair.)
You can also use the CONFIG command to activate this feature, but if so, you must OPEN #0: "SROW=1,SCOL=1", DISPLAY, OUTIN after executing the CONFIG command.
Specifying 3D FIELDS in BRconfig.SYS is not sufficient to activate it. You must also either precede a standard field attribute with 01 (e.g. U 0170) or specify S as a leading field attribute in your FIELDS specification. For example:
INPUT FIELDS "10,10,C 10,S": X$
The preferred way for legacy code to activate 3D FIELDS is to use the SCREEN statement. Ctrl-Z will act as undo when DATAHILITE is on.
Note: In very early versions, 3D FIELDS was known as FIELDS3D.
See also Datahilite.