Most things in life are controlled by the bottom line. That line could be anything or take on any shape depending on what we are doing and what we want to get out of it. Using AutoCAD is no different. Regardless of your profession, design genre, or industry, the bottom line in using AutoCAD is the printed drawing. That is our product, be it construction details, concept plans, renderings, sales exhibits, maps, or whatever. We provide drawings. Regardless of the type or purpose of our drawings, they must visually display the information, thoughts, and ideas we want to convey. If not, then they are worthless.
There are many ways to force our CAD files to look pleasing to the eye. We also have to keep in mind the processes and the behind-the-scenes acts that go into a design and its drawings. Do we sacrifice ease of revision work to make a quick drawing or do we take the time to organize the data in our models? Users are likely to disagree, but more times than not, organizing your data makes revision work much easier.
The three rules of AutoCAD objects
Each object type in AutoCAD has three major properties that can be altered. They are Color, Layer, and Linetype. You could even include lineweight; in fact, let's do. Perhaps it is more appropriate to look at the three qualities in an object as being: Color, Linetype, and Lineweight.
There are two ways of controlling these features - by layer or by object. Defining an object's visual display by layer means that the three main properties are controlled by the object’s layer. The alternative is to manage these properties on an object by object basis. Most commonly, though, in practice, you will find users taking a hybrid approach. They will control the visual display through layers, with the occasional "by object" thrown in here and there. This is probably okay; however, using layers to manage your display features is a much preferred method of control.
Figure 1: The Quick Properties window in AutoCAD 2010 visually displays the basic properties of the selected object.
What's the difference?
Why is it better to control visual properties of objects bylayer as opposed to by object? If an object’s color is set to anything besides bylayer, then your options for the object are now limited. In fact, they are dead. There is no choice but to display that object in any other way, except for the color that was assigned to it. If it is bylayer, then it can be displayed in any color, in any viewport, on any drawing, at any time. That is far more powerful than locking it in to one certain color. The same goes for object line type and lineweight. Once these are set on the object, then the layer can no longer manage the object’s property.
Why keeping control by layers is important
When an object’s properties are set to bylayer, then the layer controls those display values. That means the files can be referenced in a drawing file and displayed according to the needs of that drawing. Circumstances are going to be different from one project to the next, and from one design firm from the next, but the idea is similar. In any given project, typically speaking of course, there will be background information and design information. In the case of a Civil Engineering project, the background information could be an existing conditions map or a land survey. The new information, or design information, could be a new road, berm, or retention pond. However, to the surveying department, that land survey is the design information. The data will mean different things to different groups at different times in the life of a project.
Instead of repeating data, draw it bylayer, reference it, and display it according to your needs. The surveyor can display the linework dark and thick, while the civil engineer can fade the lines to the background. Both have what they need and both have current data. Drawing bylayer isn’t just for your benefit, but for the benefits of your project partners as well.
Figure 2: The Layer Manager as seen managing the layers of an active viewport. The objects in the drawing were drawn bylayer so the View Port Overrides, highlighted in light blue, will control the visual display of the objects. Click image to enlarge.
If you are going to control the visual display settings with a bylayer approach, then it is important to organize your layers. Can you have too many layers? Perhaps... that will depend on your needs and size of your project. If there are different levels, phases, or aspects to your project then you may need more layers than you would on a simpler project. That is okay. The layer manager in AutoCAD has a filtering system that will help users find the layer they need.
A good practice that helps is to group your layers by giving them similar names. For example, if you have layers that will contain existing linework, then start each layer name with the word EXISTING. When you sort your layers alphabetically, then all of the existing layers will be next to each other. If you have different departments working on the project, start the layer names with that department (e.g., survey). There are several different layer naming procedures that are part of a group or industry. The United States has a National CAD Standard that has a layer naming procedure in it that works in a similar way that was just described. The exact way you organize your layers doesn't matter. It only matters that there is a plan or procedure in place.
Figure 3: The Layer Manager from a file containing many layers. The designer managed the layers in groups by starting the layer names with similar terms.
Making drawings is what we are trying to do when we use AutoCAD or any other CAD or GIS program. How those drawings appear on paper is essential to conveying our message to our clients. In order to make sure our drawings are drawn the way we want them to be, it is important to develop a standard to manage that display system. Drawing your objects with a bylayer setting and controlling the display values through layers is a good way to accomplish this. Developing a layering system that is consistently applied to your model files is one of the best procedures that you can take to help this process. The exact details are not what is important; just having a plan in place will make all the difference.