draw it once

31 May, 2003 By: AIA ,H. Edward Goldberg

The best way to use CAD is to "draw something only once." Take advantage of block, cell, copy, and reference capabilities to increase productivity by reusing predrawn elements. Today, you can find many sources for 2D content and intelligent 3D content, which is even more useful.

AutoCAD blocks and MicroStation cells are very easy to create. You can make any series of entities, 2D or 3D, into blocks inside most CAD programs. When AutoCAD inserts any standard drawing into an existing drawing, it inserts it as a block. A block in AutoCAD is a single object, but you can explode it into its entities. AutoCAD xrefs are a variation of the block theme, but are electronically attached to their original drawing, so when you make changes, the original updates.

For 3D intelligent content, Autodesk Architectural Desktop uses Styles, and ArchiCAD, among others, supports the IFC (Industry Foundation Classes) intelligent content. GDL (geometric description language) is another intelligent content system supported in ArchiCAD. All of these methods use programming to control content rather than the drawn entities used in blocks. Autodesk uses i-drop technology that lets you drag and drop content or style information from the Web directly into your drawings. The new 2004 versions of AutoCAD and Architectural Desktop use a Content Browser that automatically updates from the Web. Whether it's 2D or 3D, literarily thousands of blocks and content files are available on the Internet and from third-party software developers. Some of these libraries are for sale, and some are free.


GDL Central
Figure 1. GDL (geometric description language) contains all of the information necessary to completely describe building elements as 2D CAD symbols, text specifications, and 3D models for calculations and presentations.
The IAI (International Alliance for Interoperability) continues to promote IFC objects, standardized AEC 3D intelligent content that represents all parts of a building. IFC2.x is the latest version. Autodesk Architectural Desktop 2004, Bentley's Triforma, Graphisoft ArchiCAD, and Nemetschek VectorWorks are among the software programs that can use IFC information. GDL has been continuously developed since 1982. It's mature object technology, with tens of thousands of highly parametric objects available and in use around the world. GDL contains all of the information necessary to completely describe building elements as 2D CAD symbols, text specifications, and 3D models for calculations and presentations (figure 1). You can download a GDL adapter for AutoCAD and download content at Objects Online.

Users of visualization programs have posted lots of free 3D content on the Internet. You can use this content as 2D blocks, but they contain redundant vertices. If you use Architectural Desktop, you can create 2D blocks from any 3D content by using the Hidden Line Projection command. If you own Rhino by Robert McNeel and Associates, you can convert 3D content into 2D content by going to Dimension | Make 2D Drawing.

Much has changed in the three years since my last column on block libraries (Cadalyst, July 2001). Not only is CAD software changing from emphasizing 2D electronic drafting to parametric 3D building models, but the integration of the Internet into our workplace is also evolves. Manufacturers of building components have also become more CAD savvy to entice architects and engineers to use their products. With the advent of XML for the Internet and downloadable specialized programs, many manufacturers allow us to gain access and to customize content before inserting it into our programs. The following are just a few of the sources for block libraries and content available to the AEC CAD user.

Although not meant as a block library, the Architectural Graphic Standards CD-ROM ($425) contains more than 10,000 drawings, all in DWG, DXF, and DGN format for easy insertion in your drawings. The drawings are available online via subscription.

Andersen Window
Figure 2. Andersen’s Window Studio software is one of the best stand-alone design tools provided by an AEC manufacturer.
Window and door manufacturers were among the first distributors of CAD blocks, and Andersen is a leader. Its new Window Studio software is one of the best stand-alone design tools available from an AEC manufacturer. With it, you can choose any window configuration Andersen manufactures and download elevations and sections in DXF, DWG, and WMF (figure 2). Andersen also has a Web-based tool that provides the same blocks as Window Studio. It would be even more helpful if door and window manufacturers would also create IFC- or Styles-based information so that we could just as easily add their content to BIM (building information modeling) and intelligent 3D AEC software programs.

Figure 3. The Autodesk Web site contains Styles that automatically control intelligent AEC content in Autodesk Architectural Desktop.
Data and downloads are directly accessible from inside all Autodesk products. The Autodesk Web site contains Styles that automatically control intelligent AEC content (figure 3). Go to the Web site and select Architectural Desktop, and then Data & Downloads. Autodesk's Architectural Symbols 2000 ($99) offers more than 12,000-4,000 are new-symbols to help you tailor AutoCAD 2000-2000i and AutoCAD LT 2000-2000i for architectural, mechanical, and electronic design and drafting.

Figure 4. At the CADBLOCKS.NET site you can find almost any block you might want.
On this free CAD site you can find practically anything you want, including ADA (Americans with Disabilities Act) blocks and some 3D content (figure 4). This is a nicely organized site with interactive content displays. Be sure to check out its free AutoLISP routines and hatches.

Block Master Pro 2.3 and Block Publisher 1.2 can help you manage interactive blocks. Block Master Pro organizes your block library

Figure 5. Block Master Pro 2.3 from Designs by Academix.Inc. helps you organize your block symbols into categories.
symbols by category into a tree format (figure 5). Among its features is the ability to individually control each block property, including insertion scale, layer, creation unit, and description. Block Publisher lets you prepare printed CAD manuals of your current symbol libraries. Block Master Pro 2.1 sells for $99.99. Block Publisher sells for $69.99. Also check out the company's other AutoCAD-based programs. Many other block management utilities are available, this is just a short list of a few.

Figure 6. Once you register at Fastrackcad, you can download a variety of details, elevations, and 3D block content in DWG and DXF formats.
For those of you in the United Kingdom, this great site is similar in content and format to (figure 6). After you register, you gain access to dozens of details, elevations, and 3D block content in DWG and DXF formats. The information is listed alphabetically by manufacturers, and you can order a CD-ROM of the content.

This four-year old site is for AEC, MCAD, and CAD technical professionals. Though the site doesn't contain content, it has an excellent search engine. Just type Blocks in the search field and take a look at the 701 sites that lists.

Thomas Register
Figure 7. Thomas Register has a new online toolbar that you can add to your Web browser to help you download blocks.
Thomas Register publishes books and CD-ROMs of manufacturers' content (figure 7). It produces and publishes three free CD-ROM libraries of CAD drawings and technical data. PartSpec contains millions of parts and is an essential tool for mechanical and electrical engineers and designers.

PlantSpec contains CAD drawings of parts and technical information for use by plant designers, engineers, and facilities management. CADBlocks provides architects and facilities engineers with thousands of drawings and technical data of building products from top manufacturers.

Thomas Register has a new online toolbar that you can add to your Web browser. With this toolbar, you can quickly download content and pictures of products. Go the Web site and download the toolbar, or sign up for the free CD-ROMs.

As I've said before, there is a lot of free content on the Web, but much of it is primitive. Be selective, and don't get frustrated. You can never have too many blocks.

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