You can make many changes to inserted CAD drawings without converting them. However, you cannot delete, resize, or modify the objects in a drawing unless you convert them to Visio shapes. And if you have an existing library of CAD symbols that you want to use in Visio diagrams, you probably want to convert them into reusable master shapes. Because a typical CAD drawing can include hundreds or thousands of objects, it's best to convert selectively. Visio lets you convert objects in a CAD drawing that you've already imported on the basis of their layers or levels. You can also convert several CAD drawings and all their layers at once.
Converting a CAD drawing brings to light the very different natures of the DWG/DXF file formats and the Visio file format. As one Visio product planner put it, "CAD is just a bag of vectors." When you convert a CAD drawing, each vector is converted to a shape, as Figure 17-12 shows. For example, the four lines that make up a rectangular room in a CAD drawing might become four Visio shapes—one for each wall. By contrast, a room shape from the Walls, Doors And Windows stencil is just one shape no matter how many lines it contains. In addition, the speed with which Visio can redraw the display is based on the number of shapes in a drawing, so more shapes means slower performance.
Figure 17-12. When you convert a CAD drawing, each line in the drawing becomes an individual Visio shape that you can select.
After you import a display-only CAD drawing, you can quickly convert it to Visio shapes with the Convert Wizard. In the wizard, you choose the CAD layer or level that contains the objects you want to convert. The three-step conversion process can take a few minutes, depending on the complexity of the CAD drawing; the number of layers or levels you're converting; and the speed of your machine. After conversion, the objects in the CAD drawing will appear as an outline. You can then group, edit, or add them to a stencil. In short, you can do anything with them that you can do with any other Visio shape.
Follow these steps to convert CAD objects to Visio format:
Figure 17-13. The Convert Wizard steps you through the options when converting an imported CAD drawing to Visio shapes.
In Step 2 of the Convert Wizard, the layers or levels you selected in Step 1 are listed, as Figure 17-14 shows. The objects on these layers will be converted to shapes regardless of the option you choose here, which determines how much of the original imported CAD drawing to retain. The wizard's language is a little counterintuitive, but these are your options:
Figure 17-14. The Convert Wizard can retain all, some, or none of the original layers of the CAD drawing as a display-only object.
You can choose how to convert dimensions and hatch patterns in Step 3 of the Convert Wizard, as Figure 17-15 shows. You have the following options:
Figure 17-15. The wizard can convert dimension lines into intelligent Visio dimension shapes. Hatch patterns can be converted to not-so-intelligent Visio lines.
You can convert more than one CAD drawing at a time with the Convert CAD Drawings add-in, as Figure 17-16 shows. Although this method is efficient when you have several drawings to convert, you don't have as much control as you do when you convert drawings individually. Each CAD drawing is converted into a separate Visio file, and every layer or level in each CAD drawing is converted. To start this add-in, choose Tools, Macros, Visio Extras, Convert CAD Drawings. Select the drawing you want (use Shift+click to select multiple drawings), and then click Open. The conversion might take a few minutes. When the process is finished, the converted files are opened in Visio.
Figure 17-16. You can select multiple CAD drawings to convert at once with the Convert CAD Drawings add-in.
Converted CAD objects become ungrouped.
The Visio CAD converter might not recognize every object or block as you expect it to. That is, you might find that some objects that appear obvious to you have been converted into smaller components, such as separate line segments. To group the components into a single shape, select all of the component's objects, and then select Shape, Grouping, Group. (Press Shift+click to select multiple shapes.)
Hidden away in the Solutions folder, Visio provides two templates specifically for the purpose of converting CAD files. You can control the way CAD drawings are converted into Visio drawings by editing the converter template that Visio uses when it performs the conversion. The converter template is a Visio file that contains default settings for converted CAD drawings. You can edit the converter template to control the following:
To edit the CAD converter template, follow these steps:
For details about changing a page's units of measure, see "Choosing the Units of Measure for the Drawing."
If you use symbol libraries in your DWG or DGN drawings, you can convert them into Visio stencils for use in your Visio drawings. You can also add the converted stencils to the converter template, so that the converter can create instances of the stencil shapes in drawings you convert, rather than having to convert each block in the drawing separately. A symbol library comprises DWG or DGN files that contain blocks or cells—collections of objects grouped together to form one object, such as a piece of furniture. When you convert a symbol library, Visio converts each block or cell into a Visio master, and it places all the masters on the same stencil. Each master is named for the block or cell from which it originated.
newfeature! When you convert blocks or cells that include multiple visible attributes, Visio creates shapes with multiple text fields to display the text as well as attribute values. For example, when an AutoCAD block is converted to create a Visio master shape, all text in block attributes is converted to custom properties of the master shape. When you drag a block master shape onto the page, Visio displays the value of the custom properties as text shapes.
Follow these steps to convert a symbol library into a Visio stencil:
When you convert CAD objects to Visio shapes, a stacking order is applied to them. This means that shapes can appear to be on top of other shapes. If the top shape is transparent, the bottom shape shows through. To adjust which shape appears where in Visio, you can change the shapes' stacking order using the commands on the Shape, Order menu (choose Bring To Front, Send To Back, Bring Forward, or Send Backward).
For details about stacking order, see "Using Stacking Order."
Converted CAD objects are no longer solid.
If a converted CAD object appears transparent in Visio and you want it to look solid, try selecting the object, and then applying a fill color, such as white. If that doesn't work, you can edit the object's ShapeSheet so that the shape can be filled, but it's a weird process.
For details, see "Drawing Closed Shapes."