Surface entity definitions consist of group codes that are common to all surface types, followed by codes specific to the type.
| Common Surface group codes |
|---|
| Group code | Description |
|---|
| 100 | Subclass marker (AcDbModelerGeometry) |
| 70 | Modeler format version number (currently = 1) |
| 1 | Proprietary data (multiple lines < 255 characters each) |
| 3 | Additional lines of proprietary data (if previous group 1 string is greater than 255 characters) (optional) |
| 100 | Subclass markar (AcDbSurface) |
| 71 | Number of U isolines |
| 72 | Number of V isolines |