University of Illinois at Chicago
School of Architecture
Bachelor of Arts in Architectural Studies Program
Arch 220 Computers in Architecture
Introduction to AutoCAD 2000
2D DRAWING ORGANIZATION using layers, blocks, xrefs and other crazy things
CHAPTER 4: Organizing a Drawing with Layers
CHAPTER 13: Creating and Using Blocks
CHAPTER 14: Working with Drawings and External References
Organizing a drawing properly in ACAD, or any other CAD software for that matter, is of utmost importance. One cannot underestimate the value of properly sorting elements in a drawing for ease of editing and output. A drawing done haphazardly can create incredible headaches for a user, as well as create real problems which have cost implications and liability issues. From the start, one must approach a CAD drawing with a lot of discipline. The main tools are:
1. LAYERS - these are the most effective way of separating elements and organizing information on a drawing file. This is a MAJOR concept in creating both 2D and 3D models.
2. BLOCKS - are elements which are user-defined; these are repetitive drawings which can be inserted into a drawing in order to save drawing time. Think of them as rubber stamps which are scalable and editable.
3. XREFS - are essentially blocks, but are much more powerful and complex. These are files which are inserted into other files to serve as references to aid drawing. XREF stands for 'external reference'.
TIPS AND TRICKS
1. Layers control color and linetype. It is very important that an object's color and linetype are controlled by the "Bylayer" option. This allows you to change the properties of elements on a single layer at a single blow. A very important command is the PROPERTIES command.
2. Learn how to use the Layer dialog box effectively, to manage the different layers by turning them on/off, freeze/thaw, etc.
3. Remember that colors determine the line thickness, and layers determine color.
4. You can have layers with the same properties (color and linetype), even if they represent different elements. It's always good practice to imagine what an object/layer's heirarchy in the plotted output should be, whether a light lineweight (a floor pattern hatch), or a very heavy line (like a wall that's cut through).
5. The CURRENT LAYER is where all objects are created. Get into the habit of changing the current layer before drawing anything.
6. Layer structures and conventions can vary from person to person. More importantly, these can also vary from drawing type to drawing type. Many firms have different layer structures for drawings of floor plans as opposed to elevations, sections, reflected ceiling plans, etc.
7. Layer names should be logical and easily understood. The use of numbers and symbols can help organize a complex set of names.
1. Blocks are dependent on the layer they are created on. If you create something on Layer 0, they become 'chameleons', assuming the color and linetype of whatever is the current layer they are inserted on.
2. Be careful in inserting blocks; make sure they are placed on the desired layer.
3. Also be careful in creating blocks with a consistent insertion point. This becomes the point in which an object enters the drawing.
4. You can make blocks into separate drawing files, to share with other users. Similarly, you could actually insert a drawing into another one, and it stays a block until it is exploded.
5. Avoid exploding blocks unless you have a good reason. Drawings can become very huge when blocks are exploded, thus defeating the purpose of the block.
1. Xrefs are like blocks, wherein they are inserted into a drawing and used as reference. These are really useful when updating different drawings with each other.
2. It is good practice to use xrefs in creating plots, because the drawings can be re-inserted without making the files too big.
3. Keep a consistent insertion point
or reference point when creating drawings, (relative to 0,0 for example) this
makes it easier to keep track of an xref when it is in the drawing.