First post in the series: ACA Ceiling Grids: The Cell Component
Previous post in the series: ACA Ceiling Grids: Mask Blocks
As seen in the previous article, Mask Blocks provide a great way to hide unwanted parts of a Ceiling Grid when an item to be placed in the ceiling is larger than one grid cell. The out-of-the-box content contains several light fixtures as part of a Mask Block, but you may need to create your own, to match your office standard graphics.
Mask Blocks have two parts, one required and one optional. The required part is one or more closed 2D polylines, splines, ellipses, or circles, to define the area to be masked. The closed polylines have to be the "newer," optimized LWPolyline type. A single object will define the area to be masked. If more than one object, or "ring" is selected, they must lie completely within or outside of each other; the rings cannot cross or touch each other. The first object will be define a mask area; you will be prompted to indicate whether subsequent rings are "void areas", or holes in the mask area, or an additional mask area.
The second, optional part is additional graphics. If you use the out-of-the-box display settings, the ring(s) selected in for the first part get placed on a non-plot layer; the additional graphics provide the plotable graphics of the Mask Block. The out-of-the-box luminaires that would span two square tiles (2'-0" or 450 mm square) are Mask Blocks with a Multi-View Block for the additional graphics. For the out-of-the-box General and Reflected Display Representations of Mask Blocks, the additional graphics end up on Layer 0, with ByBlock attributes. As these are nested within the Mask Block object, they end up inheriting the properties of the layer on which the Mask Block is placed.
The first step in creating a Mask Block is to draw the closed 2D polyline(s), spline(s), ellipse(s), and/or circle(s) that will define the mask. As previously noted, these items will define a component that is on a non-plotting layer if you are using the out-of-the-box Display Representations.
The next step is to create the additional graphics. For this example, I created a Multi-View Block with the plan graphics for a 4'-0" x 2'-0" supply diffuser. Place an instance of the additional graphics in the proper location, relative to the mask definition object(s).
You can now use the MASKADD command to add an instance of the newly created Mask Block Definition and attach it to a Ceiling Grid.