by Dennis Collin
When working with building plans for space planning or facilities management, there is often a need to show areas as well as structural elements, notes, and dimensions.
Fig 1. Using Fields in a building floorplan.
Although AutoCAD does have an area function it is still somewhat cumbersome, and users require a more efficient way of accurately showing an area that relates to the drawn geometry.
Fields are elements that are designed to hold information that synchronises when changes are made. Fields can also contain information, such as File creation date, File Name or Location, Sheet Number, or User Login information. They can be used within standard multi-line or single line text objects, attributes, and tables.
To link a text entity to an area, create a multi-line text entity, I recommend multi-line text over single line text due to superior formatting options, background mask capabilities and the ease to which squared and other symbols can be added.
Fig 2. Accessing the Insert Field Function
When creating the Mtext object right click and choose the Insert Field option on the right-click menu. (Alternatively use the button on the ribbon menu)
Choose Object from the drop-down list and choose the area property. Select formatting and units to display .
Fig 3. Configuring the field to show correct area units (SQM)
Possible elements include any enclosed object including circles, polylines, and regions. Personally, I recommend using Hatches for area calculations. For two reasons, not only do they highlight the relevant area in a drawing, but hatch elements are also more robust than a polyline and have the added benefit of showing a net area of a room. This is useful in Architecture and Space Planning when certain areas like risers or structures need to be excluded in area computations. Polylines might be useful when measuring gross areas of areas or buildings.
When the polyline or hatch is modified, and the drawing saved, or the screen is refreshed with the ‘REGEN’ command the area field will update with the new area. Take care when using commands like Explode on Polylines as that will break the relationship between the boundary and the displayed area. Exploding Hatch elements is rarely good practice in AutoCAD!
A linked field element can be recognised with a grey background. This is useful when working on drawings. However, the grey background doesn’t print on drawings. But it may show when using screen capture software. If this is not required the grey background for all fields can be disabled within a drawing with the FIELDDISPLAY system variable (0=Off, 1=On)
Display areas dynamically is just one application of Field Elements, they can also be applied to title sheet components. I will discuss these aspects in a future blog.