Revenge of the paper space cadets31 Dec, 2000 By: Mark Middlebrook
In my July 2000 column, "Lost in paper space", I took on the contentious question of whether to use paper space as your standard operating procedure to set up all AutoCAD drawings. I compared several xref and paper space methods and argued that a model file and sheet file approach using only xrefs and model space solves many of the presentation problems that paper space is designed to address. I argued further that the xref-only methods are in many cases simpler, more flexible, and more robust.
That article unleashed a flood of e-mail from both supporters (the x-ruffians) and dissenters (the paper space cadets). This month, Ill pass on and respond to some reader comments and also cover some additional techniques and ideas.
we all just get along?
To reiterate, I was not arguing that paper space is useless. Its indispensable for some kinds of worknotably presentation of 3D modelsand useful for others. I argue against an unexamined acceptance of paper space as standard operating procedure and for a reasoned examination of the merits and disadvantages of different paper space and xref methods. All AutoCAD users should be comfortable with a variety of drawing organization methods, including ones that use paper space. This familiarity helps you choose the methods that work best for your industry, office, and project. It also ensures youll be able to understand and work with the different kinds of drawings that your clients and coworkers throw at you.
Your responses reminded me that different CAD industries have different customs and requirements. AutoCAD users in the mechanical industry are almost unanimously in favor of paper space as standard operating procedure, while those from architectural and engineering offices are more divided. Most of my experience is in creating construction documents for buildings, so my advice and opinions invariably reflect that perspective. In particular, the model file and sheet file approach to creating plot sheets appears to be most applicable to building drafting.
I recently helped two client firms with major revisions of their CAD standards. Both are structural engineering firms, and they have roughly the same number of full-time CAD drafters who use AutoCAD and engineers who review and plot drawings using AutoCAD LT. In each case, we considered the "how to organize plot sheets" question early on and debated the merits of various paper space, xref, and hybrid schemes. Interestingly, the two firms came up with very different decisions about AutoCAD drawing organization. One decided on an approach that uses paper space for all plot sheet drawings and limits xrefs to background drawings for example, an architectural floor plan that serves as the background for the structural framing plan. The other firm chose an approach that uses model files Xrefed into a sheet file (all in model space) to create plot sheets.
Both firms made good decisions. The differences were due in part to office customs that had developed around each offices old CAD standards and in part from honest differences of opinion about which advantages and disadvantages counted more. The moral is that theres no one right way to do things. Make sure that the decision-makers understand what theyre talking about (that is, that a preference isnt due to ignorance), get all of the opinions on the table, hash them out, be willing to compromise, and agree to abide by the final decision.
Several readers wrote to point out some particular situations that I didnt mention where paper space holds an advantage over other methods:
layer settings with clipped xrefs
Even we x-ruffians have to admit the advantage of paper space viewport layer settings. You can create two or more viewports that show the same model and change layer properties separately in each. For example, you can draw a floor plan and reflected ceiling plan together in model space, then show it in one paper space viewport with the reflected ceiling plan layers visible and in another viewport with only the floor plan layers visible.
But we wont
give in without a fight. This trick lets you show layers differently in
different clipped versions of the same xref. Heres how to xref and
clip a drawing called PLAN.DWG twice, with different layer settings each
Now you have separate sets of xref layers for each attachment, which you can manipulate separately in the layer dialog box. In this example, you have a group of layers named Plan_clg|* corresponding to the first instance of the xref, and a second set named Plan_flr|* corresponding to the second instance of the xref.
I admit that this method is less direct than putting the cursor in a paper space viewport, opening the layer dialog box, and turning off layers by clicking in the Active VP Freeze column. But the "modified xref name" kludge does have one advantageyou can change other layer properties, such as color or linetype, in individual instances of the xref.
ultimate in paper spaceyness: detail sheets
Ive argued vehemently and often against one particular use of paper space: assembling detail sheets that contain details of different scales. In the common version of this approach, a hapless paper space cadet creates a flock of paper space viewports, one per detail, and zooms and pans inside each one until the appropriate detail appears. After all of that thrashing about in paper space, you often end up with performance problems.
The July article describes my preferred xref and model space method for creating detail sheets, but Ive recently run across a different paper space method thats considerably more elegant. This new method is a bit tricky to describe and name, but lets call it multiple, overlapping, full detail grids.
Start with a checkerboard-like
grid of detail modules that fills the drawing area of your sheet. For
example, you might have a 4X3 grid of 7.5"X7" detail modules,
which fit the drawing area of a 36"X24" sheet with some room
left for margin and title block. Make one copy of this full-detail grid
in model space for each detail scale that you want to use (1/2"=1'-0",
3/4"=1'-0", 1"=1'-0", and so on). The detail grid
for each scale is scaled up by the corresponding drawing scale factor
(24, 16, 12, and so forth.). In paper space, you create one large viewport
for each detail grid, and you zoom each viewport according to the scale
(1/24XP, 1/16XP, 1/12XP, etc.). All of the viewports overlap exactly and
fill the drawing area of the sheet (the area not occupied by the title
block). The result is a paper space arrangement that shows all of the
detail modules at all of the possible scales. To draw a detail, zoom in
model space to the detail grid for the scale that you want to use. Draw
the detail in the first module thats not occupied in any of the
detail grids. Figure 1 shows schematically how this method works.
Figure 1. The multiple, overlapping, full detail grids detail sheet method.
Here are some additional
things to keep in mind:
I continue to prefer the modular one-detail- per-DWG file approach for the reasons that I gave in the July article. But I recognize that its not the best approach for everyone. My co-columnist Michael Dakan and I have encountered the multiple, overlapping, full detail grids method in at least two different design firms, so this new faction of the paper space cadets may be on the march. X-ruffians beware!