dimensioning in autocad answer
Hi and Welcome to AutoCAD Forum,
as much as i understand your issue that you need to make dimensions for a 3d model , I suggest to start from here . >> Click <<
Imad Habash
Are you asking about 3D dimensions, or 2D dimensions in an isometric 2D drawing? The latter can be done with DIMROTATED to have the dimension lines go in the directions you want even if their definition points are not aligned in that direction, and DIMEDIT's Oblique option can skew the extension lines appropriately [read about it].
Kent Cooper, AIA 