Autodesk 00128-051462-9310 User Guide - Page 2111

WARNING If you overwrite one property set definition with another, you may lose data. For example, a drawing might contain a property set definition with a number of manual properties. The property set is attached to doors with the manual properties entered, and is included in a schedule table. If you overwrite this property set definition with one that does not have the same properties, the values entered for the manual properties are lost. In addition, any columns in the schedule table that reference these manual properties are flagged as invalid. Changes to the schedule table that result from changes to the property set definition are displayed the next time the table is updated manually or automatically. Understanding Automatic Properties The data in an automatic property is obtained from individual objects or their styles and is not entered manually. For example, a number of doors might have the same style but different widths. The automatic property Width may be different for each door. However, those doors have the same thickness, because thickness is a property of the style. The automatic property Thickness has the same value for all doors of the same style. For more information, see "Adding an Automatic Property Definition to a Property Set Definition" on page 2083. More than a 1,000 automatic properties are available in AutoCAD Architecture 2008. Most are self-explanatory, but a few need additional explanation. Wall Area Properties The following 4 automatic properties provide data for wall area calculations: ■ Area-Right Gross ■ Area-Right Net ■ Area-Left Gross ■ Area-Left Net The right and left sides of a wall are determined as if you were standing on the start point of the wall and facing the endpoint. Gross area is the area of one side without allowing for holes for openings such as doors and windows. Net Area is the area of one side of a wall after holes are cut for openings. Gross Area might be used to determine the quantity of gypsum board needed for a wall, while Net Area might be used to determine the quantity of brick. WARNING The area of a wall is determined by adding the union of the wall components (not including body modifiers or interferences) to the area of all faces that point to the right (for right areas) or the left (for left areas). If a particular wall style has multiple components with air space between them, the wall area may not be reported as expected. For example, a wall typically used in construction has a brick exterior, an air space, and a CMU interior. A style defined for this wall might have a component for the brick and a component for the CMU, but no component for the air space. If the wall was drawn with the brick on the left side, the wall area computed for the right side would include the right face of the CMU as well as the right face of the brick. The area reported would be twice the actual area. To avoid this situation, create components for interior air spaces in wall styles, so that no interior faces exist when the wall components are unioned. The shape of a wall can be modified by adding or subtracting body modifiers. Automatically calculating appropriate areas for every possible wall shape is practically impossible. Because of this, body modifiers and interferences are not currently included in wall area calculations. Wall areas for unusually shaped walls must be computed manually. Wall Volume Properties The following 4 automatic properties provide data for wall volume calculations: ■ Volume-Gross ■ Volume-Net ■ Volume-Gross With Mods ■ Volume-Net With Mods Gross volume is the volume of wall components without allowing for holes for openings such as doors or windows. Net volume is the volume after holes are cut for openings. You can obtain the wall volume with or without wall body modifiers. ■ Gross and net show the volume of the wall components as if no body modifiers exist. Understanding Automatic Properties | 2071