One of the most powerful abilities of AutoCAD is the ability to place pieces of the drawing on different "Layers" which may be assigned different colors, may use different linetypes (dashed, dotted, etc.), and may be turned off or on upon the user's desire. Layers may also be "frozen" which turns off the layer and does not regenerate it when zooming in or out, thereby saving much time in making the drawing. One layer is called the "current" layer, which is the one that is currently being drawn on. In architectural drawing, it makes good sense to draw the building's walls on one layer, the doors on another, and the windows on a third. In addition, there should be separate layers for dimensions, notes, drawing hatching, symbols, title block, and furniture.
Ideally, every floor plan in a complete set of drawings will contain all information on it which is used by all disciplines: column lines, structural columns, slab edge locations, stairs, partitions, window walls, doors, dimensions, general notes, as well as pipes, ducts, electrical devices, sprinkler heads and piping, beams, joists, light fixtures, speakers, ceiling grid, access panels, etc. All of these items can be shown on the same drawing and simply frozen and thawed when needed or not. Therefore, a change to the arrangement of partitions will effect immediately the duct layout, for instance, and this will be seen by thawing both of those layers.
This ability has not formerly been available
to architects and coordination of the various disciplines' individual elements
has been fraught with potential error. The use of so-called "overlay" system
of drafting in which all partitions are drawn on one sheet, column lines
on another, and ductwork only on another has helped to alleviate some of
these problems, however, it has made the organization of the work tasks
much more difficult. Finally, with CADD, one can see every aspect of the
building together and overlaid one on top of another, in different colors,
so that coordination is greatly simplified.
How to Create Layers and Assign Colors
and Linetypes to Them
The easiest method of dealing with layers
is to use the "Layer and Linetype Properties" dialogue box, which can be
invoked either by the pull-down menu by selecting "Format", and then "Layer...,"
or by clicking on the "Layers" icon on the Object Properties toolbar. Either
of these actions will bring up a well-organized dialogue box which will
allow you to create new layers, select a already-made layer to make it
current, change the color and linetype assigned to one or more layers,
freeze or thaw layers, and create new layers.
To create a new layer, select the "New"
button and fill in the name. It will automatically be assigned the white
color and continuous linetype.
To make a layer "current," select the layer you want to make current (only one), by picking the name with the "pick" button on the mouse. This will illuminate or highlight the line containing the layer name by turning the line blue. All layers which exist in the drawing are listed on the dialogue box "Layer Name" list. Once you have picked the layer name you want to make current, click the pick button on the "Current" box until the name you selected appears after the words "Current Layer:" in the upper left hand corner of the dialogue box. Then pick the OK box. This will take you back to the drawing.
Color:
When a line, arc, or circle is drawn, it
is always drawn on the current layer, and is drawn in the color and the
linetype which are assigned to that layer. To change the color of a layer
or several layers at once to a new color, pick the layer or layers you
want to reassign, then pick the box to the right of one of the layer names
which has a color in it. This will bring up another nested dialogue box
which will graphically indicate all colors which are available. 256 colors
are available in AutoCAD. It does not really matter initially what color
you assign to a layer, since this can always be changed later. When a color
assigned to a layer is changed, all objects drawn on that layer change
their color at once. Assignment of color to layers is important in helping
to discern one layer from another and in setting lineweight when plotting.
Color Numbers
1 -- red
2 -- yellow
3 -- green
4 -- cyan
5 -- blue
6 -- magenta
7 -- white
8 -- dark gray
9 -- dark red
10 -- olive drab (gray green)
11 -- dark green
12 -- dark cyan
13 -- dark blue
14 -- dark magenta
15 -- light gray
Another property of a layer which can be changed is the "linetype" associated with it. Linetype is the appearance of the line relating to its solidity or openness (solid (continuous) lines, or dotted or dashed lines). Unlike colors, however, before you can assign a particular linetype to a layer, you have to "load" them into the drawing database. You can either preload all of the linetypes or you could load them on the fly while you create the layer.
The linetypes which are commonly used in architectural drawings are the following:
DASHED ---- ---- ---- ---- ----- This is a series of short lines with spaces between them. It is used for large objects which are located beyond another object which hides it.
HIDDEN: -- -- -- -- -- -- -- -- This is just like the "DASHED" linetype with dashes and spaces between the dashes half as long as the "DASHED" linetype. This is used for smaller objects which are located above or behind the viewer.
HIDDEN2: - - - - - - - - - - - - - - - - This is just like the "HIDDEN" linetype with dashes and spaces between the dashes half as long as the "HIDDEN" linetype. This is used for objects which are located above or behind the viewer.
CENTER: ---- - ---- - ---- - ---- - ---- This is a long dash followed by a short dash. It is used for column centerlines.
PHANTOM: --- - - ---- - - ---- - - ----
This is a long dash followed by two short dashes. It is used for property
lines.
How to Change the Visibility of Layers
Turning Layers "Off" or "On"
You may turn any layer "off" or "on." An "off" layer will not be visible, thus will not plot and normally cannot be edited because objects on Off layers cannot be selected with the cursor. A good example of when this would be used is when you are working on a floor plan and want to see only the walls and doors, but do not want to see notes, column lines, furniture, door numbers, and dimensions, because they are cluttering up the drawing. The layers on which the notes, column lines, furniture, door numbers, and dimensions may be turned Off so that you have a clear view of just the walls and doors. Off layers will not plot.
The technique of using many layers in your drawing and turning layers Off at times when it is not necessary to view those objects is extremely useful for coordinating mechanical, plumbing, and electrical objects with architectural and structural elements. All aspects of any plan, for instance, including, the architectural floor plan information, doors, door swings, text, dimensions, structural information and text, mechanical ductwork layouts, electrical lighting, architectural reflected ceiling plans, electrical power plans showing conduit and outlets, plumbing and process piping drawings, and communications information, can all be shown on the same drawing, and edited as required together, so there is no loss of information or coordination between drawings.
To turn a layer Off, select the select the Layer Control Dialogue Box and click on the layer name you want to freeze. If you want to select more than one layer, hold down the "Ctrl" key after you have selected the first layer. If you want to select several layers in a row, pick the one at the top of the list of layers you want to select, and then hold down the "Shift" key and pick the one at the bottom of the list. All layers in between the top and bottom selection will be highlighted. Then click on the light bulb image on one of the highlighted layers. The lightbulbs to the right of all layer names you have highlighted will then turn blue, depicting an "Off" state. If you wish to turn only one layer Off, this can be done by simply clicking on the lightbulb icon in the pull-down layer list. Entities on Off layers have not been deleted from your drawing, they are still "there," that is, they are still in the drawing database, but they have been made temporarily invisible to you.
Commands such as Erase, Move, Copy, Rotate and Scale allow the use of the "All" selection methods (such as "Command: E<RET>ALL<RET"), which means that ALL objects, regardless of whether they are placed on a layer that is turned Off, will be selected. So be very careful when using the "All" selection mode. Conversly, if you want to move the entire drawing over and some layers are turned Off, if you select objects using the pick box or window (rather than "All" or "Previous" or "Last"), objects on the Off layers will be "left behind." You may be suprised when you turn those layers back On and some objects are no longer where they are supposed to be. So if you want to move everything over, and layers are turned Off, either turn those layers On before you make a selection, or use the "All" selection method.
Also be careful not to turn the "Current" layer Off. You will be drawing objects on that layer, but what you draw wil not be visible until you turn the current layer On.
("Freeze" and "Thaw" Layers)
You may also "Freeze" or "Thaw" any layer. Freezing a layer will have the same effect as turning that layer Off, that is, it will make all objects on that layer invisible. In order to make objects on a frozen layer visible again, "Thaw" the layer. Sometimes you will need to regen to make them visible after thawing. Just like turning layers Off, only objects which are visible on the screen on On and Thawed layers can be selected for moving. The main difference between Off/On and Freeze/Thaw commands is that objects on Frozen layers are not included in an "All" selection.
To Freeze a layer, select the select the Layer Control Dialogue Box and click on the layer name you want to freeze. If you want to select more than one layer, hold down the "Ctrl" key after you have selected the first layer. If you want to select several layers in a row, pick the one at the top of the list of layers you want to select, and then hold down the "Shift" key and pick the one at the bottom of the list. All layers in between the top and bottom selection will be highlighted. Then click on the sun image on one of the highlighted layers. The sun to the right of the right of the lightbulb on all layer names you have highlighted will then turn into a snowflake icon, depicting a "Frozen" state. If you wish to only Freeze one layer, this can be done by simply clicking on the large sun icon in the pull-down layer list. Entities on Frozen layers have not been deleted from your drawing, they are still "there," that is, they are still in the drawing database, but they have been made temporarily invisible to you. If you want to Thaw a layer, use the pull-down layer list and click on the snowflake. This will turn it into a sun and thaw that layer or layers. You may need to REGEN to see thawed layers after they have been thawed.
Note that you are not permitted to freeze the current layer, so if you want to freeze all layers other than the current layer, a very convenient method is to type the following at the Command: prompt: -la <RET> f <RET>* <RET><RET>. The * (asterisk) is a wildcard meaning "all of the layers." Because you cannot freeze the current layer, it will remain visible, and objects on all other layers will be made invisible.
Locked Layers
Layers may also be "locked," which will have similar to their being frozen, except that the locked layers will still be visible on the screen, and you can use their entities to snap to points. To lock layers, select the Layer Control Dialogue Box (select from the pull-down menu, "Format" then "Layer..."). In the Layer Control Dialogue Box, click on each layer name you want to lock. This will highlight the layer names. Then place a check mark in the box that has the word "Lock" after it on the bottom of the dialogue box. The padlock icon will appear as a closed padlock after the name of each layer selected. If you wish to lock only one layer, this can either be done on the Layer Control Dialogue Box by simply clicking on the padlock to toggle it from an open lock to a closed lock, or, you could use the pull-down layer list and click on the padlock.
Locked layers are very useful for giving a copy of your floor plan to a mechanical or electrical engineer. They can add their ductwork or lighting to your floor plan but not be able to change the wall locations, door locations, or column centerlines if you have "locked" those layers. Locked layers may also be frozen if desired. Entities on Locked layers can be OSNAPped to, and they will plot, but they cannot be erased, stretched, rotated, moved or copied.
How to Change Layers of entities which are already drawn