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AEC

The Lowdown on Layouts

30 Sep, 1999 By: John E. Wilson

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In AutoCAD 2000, Paper Space has been given a new look and new power. It is now almost impossible to ignore, and it is time for you to reconsider Paper Space. Let's take a look at its new abilities this month and point out what they can do for you.

For most users, Paper Space has been a tool looking for a purpose ever since it appeared in Release 11. Of course, there was a reason for creating it. In fact, there were two reasons. One was to provide a method for making 2D multiview drawings from 3D models. The multiple tiled viewports introduced in Release 10 were useful for visualizing and working with 3D models, but they could not be used for making multiview drawings-only one viewport at a time could be plotted and there was no practical means for controlling the scale of the model or for aligning views of it. Paper Space, on the other hand, could not only show the model from different viewpoints, it could precisely control the scale of the model within each viewport. You could also align the different views of the model with each other. Furthermore, you could control hidden-line removal during plotting on a viewport-by-viewport basis, hide the viewport borders and suppress the display of objects in certain layers in selected viewports.

Autodesk's second reason for creating Paper Space was to provide a way in 2D drawings to make views with a scale that is different from the rest of the drawing. For example, without Paper Space the only way to make an enlarged detail view of an area within a 2D drawing is to copy the objects in the area and then enlarge the copies. You usually also need to trim the copies, and if you add dimensions to the detail view, you must account for the objects' enlarged size. While this is extra work, the real problems with this approach occur when design changes require the objects to be changed. Not only must you change two sets of objects, you must work in two different scales. With Paper Space you can make a viewport showing just the area of the detail and then adjust the scale within the new viewport. Although you must still account for the different scale of the objects in the detail viewport when dimensions are added, design changes need to be made on just one set of objects.

Users have largely ignored Paper Space. Perhaps relatively few users have shown interest in the ability of Paper Space to create multiview drawings of 3D models because relatively few users have been interested in creating 3D models with AutoCAD. Moreover, the Paper Space approach to making 2D multiview drawings has problems of its own. One problem is that adding dimensions to 3D objects, especially when the edges are stacked on top of each other as they often are in orthographic views, does not work well. Another problem is that mesh lines that many 3D surfaces have cause serious visualization problems.

Also, few AutoCAD users have been interested in the ability of Paper Space to create detail views because it is an entirely different concept that requires an entirely different approach to 2D drafting and drawing management. Furthermore, the rectangular borders of the floating viewports could often not be made to fit the geometry of the detail view. Through the years, users have devised some ingenious-and a few bizarre-techniques for simulating nonrectangular floating viewport borders, but none of them were entirely satisfactory.

Layouts
While the two original purposes of Paper Space are still valid, AutoCAD 2000 has expanded the role of Paper Space to make it the preferred method for all output, whether it is for 2D drawings or 3D models. To accommodate this expanded role, AutoCAD 2000 has shipped with some new Paper Space related commands, has enhanced some existing commands and has even adopted some new terminology.

The term Paper Space now refers to a work environment, and within that environment are layouts. A layout is a specific combination of plotting device parameters and paper-size and floating-viewport configurations. Any number of layouts can be established for a single model. For example, within the drawing file of a 3D model you could have one layout for a multiview drawing on size D paper (34x22 inches), another layout for an isometric drawing on size C paper (22x17 inches) and another for an isometric drawing on vertical size A paper (8.5x11 inches).

Figure 1. The page layouts of AutoCAD 2000's new approach to Paper Space simulate the paper the drawing will be plotted on, including the printable margins of the paper. Options for creating and managing page layouts are displayed in a shortcut menu opened by right-clicking a layout tab.

You switch from one layout to another by clicking its tab, which is located on the bottom edge of the AutoCAD graphics window. By default two layouts having the same parameters exist. You can, though, create additional layouts, delete layouts and give them more descriptive names than the default names of Layout1 and Layout2. A new command-LAYOUT-manages layouts, but you will most likely manage them through the shortcut menu, as shown in Figure 1, that is activated by right-clicking a layout tab. Both methods, for the most part, offer the same options. A tab labeled Model, which returns to Model Space, also exists.

Page Setup
Even though the look and feel of AutoCAD 2000's layouts is altogether different from the Paper Space of previous AutoCAD releases, the process of preparing a drawing for output is similar. Your first step in this process is to choose a paper size for the drawing. In AutoCAD 2000 this is done through the Page Setup dialog box, which is displayed by either entering PAGESETUP on the command line or by selecting Page Setup from the layout tab's shortcut menu. Also, by default this dialog box is automatically displayed when you first activate one of the premade layouts and when you create a new layout.

The Page Setup dialog box is almost a duplicate of the Plot dialog box. Its primary purpose is to establish the layout's size. Consequently when you click its OK button, no printing occurs. The dialog box has two tabs: one is labeled Plot Device and the other is labeled Layout Setup. The Plot Device tab is for choosing and, if necessary, configuring a plotter. While the Layout Setup tab is for selecting a paper size, only paper sizes that the chosen plotter can handle are available for selection.

You can also set plotting parameters with this dialog box, but since you'll get another chance to set them as you plot the drawing, it is not essential that you do so here. You will notice in the dialog box that Limits has been replaced by Layout as an option for the area to be plotted. The layout area is the space that is within the printable margins of the paper. For example, you may have selected a 22x17 inch paper size, but since the plotter needs some space for gripping the paper, the printable area might be only 21x15 inches. The origin for the layout's coordinate system is on the lower-left corner of the printable area. The settings in the cluster of buttons labeled Plot Scale control the actual plot size relative to the layout size, rather than to the scale of the drawing views. Unless you want to do something unusual, such as print a size C drawing on size A paper, you will use one-to-one as the scale.

When you exit the Page Setup dialog box, by default AutoCAD simulates a white sheet of paper corresponding to your paper size selection (including the margins of its printable area) and it creates one floating viewport showing your model as you last saw it in Model Space. You can change the defaults for what is shown and the paper's color through the Display tab of the Options dialog box. Although the display of a sheet of paper and its margins may at first seem gimmicky, you will probably find it useful. The automatically created viewport, on the other hand, will seldom be what you want, especially when you are working with a 3D model, and you will probably turn that option off.

Drawing Borders and Title Blocks
Once you have established the layout's page parameters, you are likely to next insert or draw a border and title block. If you have a border and title block, you will insert it as a block or xref; but if you don't, you can insert one provided by AutoCAD. Files for borders and title blocks corresponding to American (ANSI), International (ISO), German (DIN) and Japanese (JIS) standards are in the Acad2000\ Template folder. The sizes of the borders are smaller than the standard sizes so that they are more likely to fit within the paper's printable margins. You can also use the Title Block option of AutoCAD's MVSETUP command to create a title block. This option draws a border and title block that exactly corresponds to the sizes specified by ANSI and ISO drafting standards.

Wizards and Templates
AutoCAD 2000 has a wizard that uses a series of dialog boxes to lead you through the process of selecting a printer, choosing a paper size, inserting a border and title block and even creating floating viewports. One of several ways to start this wizard is to enter LAYOUTWIZARD on the command line. As an introduction to layouts, the Layout Wizard is useful, but once you understand the process (which is not hard to do), you are not likely to use it.

You can also use a template in creating a new layout by selecting the Template option of LAYOUT or by selecting From Template in the layout tab shortcut menu. A dialog box titled Select File will be displayed for you to select a drawing file (DWG) or a template file (DWT) as the basis of a new layout. The paper size of the new layout will match the selected template, a drawing border and title block will be inserted, and one floating viewport will be created. Creating a layout from a template might be your preferred method for 2D drawings, but you are not likely to use this method in creating layouts for 3D models, unless you have some template files of your own.

Floating Viewports
You must have at least one floating viewport in a layout to show your 3D model or 2D drawing. Floating viewports

• reside in a layer, and that layer can be turned off to hide the viewport's border while its contents remain visible;

• can be copied, moved, stretched, scaled and erased;

• can have gaps between each other and, conversely, can overlap one another.

You can also control hidden line removal viewport-by-viewport during plotting, precisely set the scale in each viewport and specify that objects in certain layers will not be shown in selected viewports.

Figure 2. Floating viewport boundaries in AutoCAD 2000 can have virtually any shape that can be drawn as a single closed object. Viewport shapes can even be set by the boundaries of a region, which allows you to have viewports with opaque interior islands.

The restriction that floating viewports must be rectangular, however, has been removed. They can now be circular, elliptical, L-shaped, U-shaped, have spline curved borders or virtually any other shape that can be drawn as a single, closed 2D object. They can even have opaque interior islands, as shown in Figure 2. Two different options are available for making nonrectangular viewports. The more versatile of these options uses an existing closed object-such as a spline, a circle or a polyline-to create a viewport. The existing object can also be a region, which is how you can make viewports with islands. With the other option, which is called Polygonal, you draw the viewport boundary by responding to command-line prompts similar to those of the PLINE command.

Nonrectangular viewports are probably most useful to those working with 2D drawings. They can be used to hide portions of building plans, to serve as borders of detail views, to create a viewport that conforms to a drawing's border and title block and to create a dramatic effect. Those working with 3D models are less likely to use nonrectangular viewports because they generally create floating viewports just to show their models, and then they turn the display of viewport borders off.

Another new option for floating viewports locks the current zoom level and viewpoint of selected viewports. Anyone who has messed up the scale of a view or its alignment with other views by inadvertently zooming or panning within a floating viewport (which includes most of us) will especially appreciate this option. When a viewport is locked, the ZOOM, PAN, DVIEW and VPOINT commands are disabled within the viewport. Surprisingly, though, the 3DORBIT command still functions in locked viewports.

You can also specify a scale to be automatically applied to all new floating viewports. You can, for example, specify that the viewports you make for a multiview drawing are to show the 3D model at one-half its true size. You specify this scale by assigning a value to the psvpscale system variable. By default the value of this system variable is 0, which means that the scale within new viewports is equivalent to a zoom extents.

Unlike with previous releases, the VPORTS command now works in Paper Space to create floating viewports, as well as in Model Space to create titled viewports. Its primary Paper Space format is a dialog box that has options for creating rectangular viewports in one of 10 different arrangements. As you select an arrangement, a preview of it is shown in an image tile. You can also specify that an orthographic or isometric view is to be set in the viewports as they are created.

When you invoke VPORTS from the command line and precede its name with a hyphen, command-line prompts are displayed rather than a dialog box. The VPORTS prompts are identical to those of the MVIEW command, which in previous AutoCAD versions was the only way to create floating viewports. If you intend to create nonrectangular viewports or to lock viewports, you must use either MVIEW, the command-line version or VPORTS. A new command, PVCLIP, enables you to change the shape of viewport borders. This command has options to base the new border on an existing closed object and for drawing a polygonal border.

Those of you who make 3D solid models should ignore most of the new options for floating viewports and continue to use SOLVIEW and SOLDRAW to create multiview drawings. The option to lock the view within a viewport, though, is one that you will use. You will also need to establish a page layout before you begin SOLVIEW.

It may take you some time to become accustomed to the new look and new features of Paper Space-and to its new purposes. Once you do, you will probably agree that in AutoCAD 2000 Paper Space has been given additional flexibility, power and usability.