Layers 1
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Author | Erhan Toker |
| Profession | Architect M.Sc. | |
| Autodesk Authorized Consultant | ||
| Software Specialist | ||
Most of us had some trouble about using different linetypes and colors when we introduced to AutoCAD. The basic trouble here is that linetypes and colors of Autocad drawing elements, which we call them ‘object’, can be given from the layer they belong or assigned directly. This subject may be seen as a bit complicated but it is not, besides it is effective when you get used to the subject. The one who knows how to use layers, knows using Autocad above 50%. Believe me, I am not exaggerating.
Let us start with the definition of LAYER. Think about layers in AutoCAD in that way: You are drawing in a traditional way. You draw walls on an acetate, doors on another one and likewise all parts of the drawing on a seperate acetate. Placing them one on the top of the other, you see the whole drawing. If you do not want to see the doors, you can just take the relevant acetate out. That’s exactly what ‘layer management’ does.
Considering the properties of layers on a digital platform, of course their usage is so much advanced. Let us take a look at the general properties of a layer:
Figure 1
Text or integer values are assigned according to the characteristics of the properties seen in the table. For instance, a layer color code can be 82 (from an index of 255 colors), [69,2,72] as a true color (RGB code) or ‘RAL 1001′ (color book code). Samely, other properties are assigned according to their characteristics.
Autocad drawing objects also have properties for color, linetype and lineweight like layers. Let us examine the related table below (Figure 2).
Figure 2
As you can see, the general properties of layers and objects are not different. That is because, layers are also AutoCAD drawing objects. But objects can have their properties from ‘By Block’ or ‘By Layer’ options differently from layers. This is the point that seperates the experienced and non-experienced Autocad user.
The color, linetype and lineweight properties of all AutoCAD objects are assigned as ‘By Layer’ as default. That is like saying the object; ‘take color, linetype and lineweight assignments from the layer’. Experienced users prefer this way; draw all objects in corresponding layers and change properties for color, linetype and lineweight from the layer.
The reason is simple. An architectural drawing has an average lines of 1000-1500 for walls. You could have to deal with those lines one by one when you want to change somethig if you did not define a layer for wall, draw all lines in that layer and use the properties assigned for that layer. Drawing all lines in ‘WALL’ layer, it is enough to change the layer property to change a property for all lines.
Even though this first article of ‘Layers’ is theoretical, I want to mention about setting the object properties since the subject is important. The three properties mentioned above are set to ‘By Layer’ as default when AutoCAD is opened. These settings can be seen in the menu (Figure 3).
Figure 3
If the menu is not turned on, you have to right-click on the icon menu and click ‘Properties’. For those using command line default color can be set to ‘BYLAYER’ by CECOLOR command, default linetype can be set to ‘BYLAYER’ by CELTYPE command and default lineweight can be set to ‘BYLAYER’ by CELWEIGHT command. But even for a historical command line user like me prefers icon menu since it is very practical. However, there is a trouble about icon menu. If one or more objects are selected, only those objects’ properties will change. If it is not the way you want, it is better pressing ‘Esc’ twice before using icon menu. This empties the selection set.
We should have understood by now. Default object properties should be set to ‘By Layer’. Now, it is time to create and use layers.
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