Any design firm which uses computers for more than word processing and spreadsheets will use them for drafting. AutoCAD, ArchiCAD, Microstation, and countless other programs are all examples of drafting programs, although most also do 3D modeling as well. Such programs let the user create and edit lines, arcs, circles, symbols, patterns, and other graphical entities. Typically, there are a variety of tools available to ensure that these entities are drawn accurately, so that lengths and angles are precise and intersections are neat.
One of the more useful properties of these packages is their ability to let the user repeat elements quickly and easily. Symbols can be created and inserted multiple times within a single drawing, reducing file size and allowing all instances to be changed whenever the symbol is redefined. Symbols which are used in multiple projects are put together into symbol libraries. Symbols can be taken from these libraries and used in any number of drawings, giving all drawings a unified style, and saving drafters from having to draw the same thing over and over. Data can also be associated with these symbols, and later extracted and put into spreadsheets, bills of materials, or other documents.
- To introduce the student to AutoCAD, a typical 2D drafting system, and to the concepts similar drafting systems are based upon. The student should understand how such systems differ from paint programs and modeling systems.
- To familiarize the student with the sorts of basic drawing tools found in a drafting system, and how to use them to draw neatly and accurately.
- To provide an understanding of how to create libraries of reusable drawing components, and why such symbol libraries are useful in practice.
- To continue producing images and drawings which can be incorporated into later projects.
- To continue to develop a familiarity with microcomputers.
Produce at least 3 symbols of furniture, plants, vehicles, yard lights, scale indicators, north arrows, electrical symbols, or similar objects for use in plan drawings. Do not make doors or windows, because special attributes will be attached to these, and these symbols will be supplied later. Symbols should be scaled properly so that other people can use the symbols in their 2D drafting assignments. They should be drawn on layer "0", and assigned the color "BYLAYER". They should be neatly constructed (using object snaps, filters, etc.), while keeping them fairly simple. Make certain that you use the WBLOCK command to write the symbols to separate files. You should print out a single sheet of paper showing all of the symbols you have created.
Symbols should be neatly drawn, taking full advantage of the tools and modes available that ensure accuracy. Straight lines should really be straight, parallel lines should be parallel, square corners should be square, and so forth. Lines should meet neatly at corners, and there should be no stray marks that are part of the blocks. Insertion base points should be appropriately chosen, so as to make the symbol easy to use.
You will hand in the sheet showing your symbols in class on Tuesday, May 18. In addition, you will need to turn in a diskette with the 3 (or more) files you created with the WBLOCK command, so that your symbols can be pooled together with those of others. Make certain you do this -- it will figure into your grade on the assignment. In addition, make certain that you have made backups of your work.
The instructor will create a symbol library by combining everyone's wblock files, and this library will be made available starting Thursday, May 20. This library will be in the form of a single large file that will be made available on the Intel machines in room 2115. This file will contain the definitions of all the symbols created for the symbol assignment, as well as door and window symbols, and perhaps symbols from previous semesters.
Be prepared to discuss your experiences with the software. Based on some of the standard drafting tools you used in the completion of the assignment, comment on whether you find the tools useful or time-consuming, compared to making drawings by hand. Comment on where you think 2D, object based drawing systems fit into the design process: can they be used while designing, or only to draw something that has already been designed? Why?
Projects will receive numerical grades according to the quality of the work. A project which fulfills all of the minimal requirements, but no more, will receive 8 out of 10 points (instead of the usual 7 - this is an easy assignment to mess up). Projects that do not fulfill the requirements described above will have points deducted. Projects which go beyond the minimal requirements and have more than the minimum number of blocks, or have unusual levels of craftsmanship, detail, or planning evident will receive up to 10 points.
Good projects can go beyond the minimum requirements by including additional symbols for the library, displaying attractive (but not excessive) levels of detail, or showing careful forethought in their construction. If symbols have a consistent level of detail and show consistent graphical and stylistic techniques, it indicates a certain amount of planning went into the design of the symbols.
Note that more detail does not necessarily mean better symbols. Detail is only good up to a point. Symbols get repeated may times in drawings, and all the details are drawn each time. Very detailed symbols can tremendously slow the time it takes for a drawing to redraw on the screen. Thus, you should resist the urge to make a tree symbol with hundreds of leaves, or a rug with an intricate hatching pattern. Do not bother with details that won't show up when a person plots a floor plan.
Also note that of all the assignments that will be given this semester, this is the assignment where it is the easiest to miss the minimal requirements. Symbols representing things with actual sizes --like a car, chair, or scale - should be drawn full scale. If they are not, points will be deducted. Symbols should be neat: lines should be properly made and meet neatly at corners, stray lines should be removed, and so forth. If they are not, it indicates that the tools are not being used properly, and points will be deducted. Blocks should each be saved in separate wblock (.dwg) files. If they are not, it indicates a misunderstanding of what wblocks are and how they are used, and results in considerably extra work for the instructor, so points will be deducted. All of these are common mistakes.
vector graphics
object-based drawing
symbol libraries
instantiation vs. repetition
geometric transformations
snapping
object snapping
filters
toggle switches