I was inspired by Erich Friend's blog post, "A 400 HP Pencil," on CAD issues yesterday, and I thought I'd use this time to talk a little about my thoughts on using CAD most effectively.

First off: "CAD" does not refer to "AutoCAD." I recognize that there's something cool about shortening names and creating our own "insider lingo," but that's not where "CAD" comes from--it's not an abbreviation for a particular drafting application, but an acronym: "computer-assisted drafting." When I talk about CAD, though I may sometimes use application-specific terms and processes, I'm talking broadly about approaches and conventions that work equally well in any CAD environment--AutoCAD, Vectorworks, Rhino CAD, what have you. We can argue for days about which CAD application is "better," but there are a couple of truths about CAD software: 1) there are a number of applications available, and people use all of them, even in theatre; 2) each application has its own advantages and disadvantages. Consequently, 3) it's in everyone's best interest to adhere to some standards of practice that are cross-platform.

Erich points out some good practices: use blocks/symbols whenever possible; keep your entities in cohesive groups--as opposed to single lines--whenever possible; keep in mind the amount of detail required for your particular drawing so as to keep file sizes low. These are all essential to creating useful, useable drawings.

It's important to consider drafting conventions as well. Hopefully, if you're drafting at all, you understand something about basic drafting "rules": hidden lines represent edges behind the surface closes to the viewer and are shown as thin, dashed lines; hatches should be drawn with thin lines, while section boundaries should be drawn with thick lines, etc. These conventions were developed over years of practice and have become a kind of vocabulary and grammar for mechanical drawings--for giving meaning to lines on a page of vellum. Certainly, CAD provides for much more complexity and meaning in drawings, but forgetting these basic building blocks of meaning can lead to confusion and overly-complex drawings. So, finding a way to carry them into the digital drafting environment becomes essential.

USITT has been working on a draft of conventions for CAD--hopefully that will be released soon! Until that happens, though, here are some of my thoughts on translating conventional drafting grammar to the digital environment.

Line weight. Line weight is an invaluable way to impart information about the relative importance of the geometry you've drawn: thin lines are less important, thick lines are more. But line weight is not implemented well in most CAD programs. That's fine, though: in CAD, we have the advantage of using color, which hand draftspeople did not. But instead of using color haphazardly, consider using value to make less important lines fade into the background of your screen while making more important lines pop. For example: if you draw on a black background, as I do (which is shown to be better for eye strain, by the way), consider making all of the entities which should be thin lines a darker value of a particular color, all of the medium lines a medium value of that color, and all of the heavy lines a brighter value of that color. This will make the thin lines recede into the background and the heavy lines pop, just as they do on the page. Obviously, if your drawing is eventually going to be plotted, you'll need to ensure they also have traditional line weights assigned to them, but you can turn off the unsightly visual representation of line weights on the screen.

Color. Color is a wonderful thing in CAD. With color, we have a way to differentiate more than three types of lines in a drawing (thin, medium, heavy), and we can classify and organize more kinds of information. However, picking colors at random, or having wildly varying color schemes can be overwhelming and confusing to people using your drawing. Ideally, your company or corporation will have a drafting standard which defines which colors should be used for what kinds of information, but if they don't, think carefully about why and how to use color.

What kinds of classifications do you need to differentiate? Is it important to easily see material choices? Is it necessary to separate architecture from scenery from lighting information? Do you have multiple floors to consider? Use these classifications to determine how many different colors you need to use. (And then consider using values of those colors for line weights within each classification you've selected!)

Layers and Classes. Layers and classes are wonderful and painful things. Used effectively, they can provide clarity and organization to your drawing. Used haphazardly, they can be clunky, cumbersome, and confusing. If you only have layers to play with, consider creating groups of layers for each classification of information you determined was important when thinking about color; within each group, create a different layer for each type of "line" you'll need to create. For example, I tend to group information into the broad categories of "architecture," "set designer" (for the designer's original information), and "TD" (for my work); I create, for each of these categories, layers for thin lines; thin/hidden lines; thin/ceiling lines; heavy lines; medium-weight lines; dimensions/notes; and centerlines. Why so many layers? For starters, I can easily turn them on and off for clarity. More importantly, instead of having to remember to assign color and line weight attributes to each entity, I can assign those attributes to each layer, and then assign the entities to the layer. A quick glance at the layer bar will tell me what "kind" of entity I'm looking at if I'm ever lost.

In CAD programs that have classes, this can be simplified: simply create classes for line weight/line types and layers for the information categories you've decided are important. You should be able to assign attributes (color and line type) to these as well.

Consider, as well, the more complex possibilities that CAD programs offer: create standard text and dimensioning styles; use "saved views" and "layer sets" to switch quickly from one part of the drawing to another and to turn on or off specific groups of layers, and use hyperlinks within the drawing as ways for users to access them. Careful use of these kinds of features will enable users to use your drawing like they would a packet of blueline drawing from previous generations, making your drawings more accessible and more useful.

I tell student that we live on the cusp of major changes in the way drawings are created and used. With the proliferation of touchscreen handheld devices, it's not going to be long before paper drawings are obsolete, and our shops are working from drawings on tablets and screens. Indeed, there are some shops doing this already! Today's students need to be at the front edge of this change, and developing good drafting habits that make your CAD drawings usable as digital documents--as more than simply overpowered drafting tables, whose purpose is to create paper drawings--is fundamental.