About Drawing Changes and Model Revision
As you detail your drawing, some drawing entities and information are parametrically associated to the model that it documents. Therefore, changes made within the drawing could result in design changes within the model.
For example, if you set a dimension as basic within a drawing, the dimension becomes theoretically exact. Any dimensional or geometric tolerances are deleted from the drawing as well as from the 3D model.
The design changes in the model result from changes to drawing entities that are saved within the model; including all dimensions, tolerances, cross sections, and model datums. Saving the model file with a version increase prevents loss of model data from changes made in the drawing file. After creating or modifying model geometry, such as shown model dimensions and their tolerances, or modifying the positioning of datums, the revision number of the model is incremented. Any other changes to drawing entities that are saved within the model are considered cosmetic and do not lead to a new model iteration. You can designate how to create drawing dimensions and how the model is affected using the create_drawing_dims and drawing_model_read_only configuration options.
The following drawing entities are considered cosmetic information and are saved within the drawing:
• All draft-only (non-associative) entities
• The view in which an entity appears
• The placement of an entity on the sheet
• Jogs and breaks in leaders and dimension lines
• The insertion of dimensions in notes
• The font, height, width, and slant angle of text
The following drawing entities are saved within the model and result in a new model iteration:
• Geometry changes, including modifications to shown model dimensions and their tolerances (dimension values, tolerance values, number of decimal places, and tolerance format).
• Datum position changes, including modification to the model dimensions that control the placement to model datums.