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We love to hate layers. It’s always a battle to know how many layers are enough; too few can be as limiting as too many. And there’s no shortage of opinions on where that line is. The key, though, to working efficiently with a large number of layers is being able to manage them. Just because a drawing has hundreds of layers don’t necessarily mean that they are unmanageable. AutoCAD’s layer filters provide a great way to make your layers more manageable.

As the name implies, a “filter” eliminates the unwanted or unneeded. When working with a large quantity of layers, rarely will you need to work with all of them all of the time. Layer filters can provide you with a “working subset” of your entire layer list to work with more efficiently. This month we’ll begin a dialog on both Property and Group Filters.

Property Filters are defined based on properties that are shared by various layers. Any property, or combination of properties, can be used to define a filter: status (used or unused), name, on, freeze, color, linetype, lineweight, plot style, and plot. The only property not usable is the Description. When a filter is selected, only those layers sharing the specified property (or properties) are available displayed in the layer list.

AutoCAD® comes with a default Property Filter named “All Used Layers.” This uses the “status” property (i.e., does the layer have anything on it or not) as the common denominator. This filter, which weeds out the empty layers, might be handy when revising an existing drawing, in which most of the layers you’ll need have already been used. In a new drawing, it would probably weed out too many of the needed layers.

This filter is also a useful feature for deleting unused layers. I hear someone asking, “But if this filter filters the unused layers, how can I delete them if I can’t see them in the list?” Down in the lower right-hand corner of the Layer Properties Manager, is an “Invert filter.” Check this box and you’re left with a list of unused, deletable layers.

Being in the architectural field, it is not uncommon to work with drawings that have hundreds of layers for the various disciplines or building systems represented in a drawing. These different disciplines and building systems are a perfect use for filters. In my sample drawing, the layers are based on the AIA’s layering guidelines and use the X-XXXX-XXXX format. This predictable naming format greatly enhances my ability to use property filters.

To create a property filter, select the “New Property Filter” icon (or press Alt-P). A “Layer Filter Properties” dialog box is displayed, where you specify the property’s properties! :-) I will create a structural filter, placing “S*” (without quotes) in the Name field. The bottom pane gives you a real-time preview of that filtered results, all the layers that start with “S”. Note: if the “Filter preview” box is empty, that’s a pretty good indication that your filter is defined improperly. Providing the results are what you want, you’re done. Not much to it, really.

A filter’s definition can be quite simple, as in this example, but filters can be too simple. In the above example, any layer that started with an “S” would show up. Adding a dash into the filter, as in “S-*”, would filter out any layers that simply started with an “S” but did not adhere to the standard X-XXXX-XXXX format. You could take it a step further by using “S-????*” as a filter. The purpose of the filter is to give you exactly the layers you want, not “most of them” or “a few I don’t need.”

One limitation of this filter is that it would not properly filter any structural layers that were brought in by an Xref, since Xref layers start with the reference name. To expand the filter’s usefulness, you can add multiple rows to the definition. Below, I’ve added a second row to the filter definition using “*|S*” in the Name field. If I wanted to accommodate bound xref layers, I could also add a third line using “*$0$S*”.

So, there’s your introduction to Layer Filters. They are simple and powerful, all at the same time. Have fun playing with them this month. We’ll continue in April with a few more Property filters features we didn’t have time for this month. Space permitting, we’ll move into Group filters.

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Submitted by Chris Lindner, an AutoCAD user/consultant/trainer/developer for over 19 years. Chris is a former Top DAUG winner and is currently Vice President of the AUGI Board of Directors. He serves as Director of CAD Technology for WD Partners. He can be reached at Chris.Lindner@augi.com.