AUGIWorld Magazine - January/February 2008 - (Page 21) Many users create linework and objects that are “bylayer,” using the layers to define color and linetype. Either method can be used; though using layers in the CAD files typically works best when working in Impression. If the linework is all on one layer, then layer styles in Impression will not work so well. If the files are organized with layers, then the work in Impression can easily be done with either styles or with area fills. Fill styles Layer styles One method of creating drawings in Impression is to create layer styles. These styles work similarly to other styles in AutoCAD®, but their layers control them. There are two main components to these styles—the layer and the style. Each layer will have a style assigned to it. Impression comes with many predefined styles that can be used, altered, copied, and so on. You can also create a style from scratch. The style’s purpose is to define the look of the layer. A style’s stroke, color, line type, and more can be adjusted. The same style can include fill styles, hatch patterns, and others. Once the style is created, it can be assigned to one or more layers. The ability to assign a style to more than one layer allows objects on different layers to have the same look. A word of caution, though. If you change a style assigned to multiple layers, it will change on every layer to which it was assigned. The good news is that this aspect will also quicken changes to a drawing. Another method for creating renderings with Impression is to use Fill Styles, which work similarly to Layer Styles. A fill style is created on a layer in Impression that has a style attached to it. Instead of the imported linework automatically rendering itself, the user must invoke the FILL command. After activating the fill command, the user selects the areas on the canvas to fill. Impression reads the linework and fills in the area much like AutoCAD executes the hatch command. In fact, if the linework wasn’t hatched in AutoCAD, Impression can create a hatch pattern and apply it to the appropriate areas. The fill styles are assigned to the filled objects much like the layer style is assigned to a layer. A layer style renders the objects on a particular layer while a fill style renders filled objects of a particular layer. The layer style doesn’t require any drawing to be done in Impression, but the fill styles require you to define the areas to be rendered. The fills exist on a specific layer, and the style for that layer controls the display of the fills. The real difference Figure 3: Style Manager At first glance it may appear that there is more work involved when using fill styles. That will depend on the condition of the CAD file, as discussed earlier. In order for the layer styles to work properly, the linework must be closed (a closed polyline or boundary); else Impression cannot fill the objects. It will only display the stroke for the line. The fill command works like a paint bucket. The user pours the paint in the desired area. That paint then runs out until it reaches a wall, which stops it. The fill command requires a starting point, the pick point, then renders according to the current style until it reaches the linework. This linework could be a series of lines, arcs, polylines, and so on. The fill command doesn’t care—it only needs a line so that it knows to stop. By contrast, layer styles need an object to fill—they don’t like lines. Impression was intended to work with AutoCAD, which it does quite well. Layer styles were created to work with CAD ob- jects and layers, which they do quite well. Fill styles were created to work with the lines on the Impression canvas, which is the working area of the Impression file. So which method is best—fills or layers? This will depend on the CAD linework and the deadline. If a CAD file is created with closed objects and layer styles are already created, then layer styles are the way to go. This will allow the user to create other drawings in the same project that have the same color pallet and styling. The rendering will also be nearly instantaneous. A set of styles can be saved in a library for future use. On the other hand, if the CAD file does not consist of closed objects, but the drawing is needed right away, fills will work quite well. Import the CAD file, open the desired style library, and start filling. This is often much quicker than converting the linework of a CAD file into closed objects. If the CAD file is revised, then the use of layer styles has the upper hand. If the Impression file was created this way, then refresh the geometry and the layer styles will re-render the drawing. Revision complete. If fills were used, refreshing the geometry may or may not work out so well. Most of the changes should come out okay, but keep in mind that any new linework will not have a fill assigned to it to render. Clean up work will be needed. (Note: Clean up work using the layer style might be needed as well.) Which is better? In an ideal world for Impression users, layer styles might be better. This would require the CAD work to be created with closed objects. Not all work is done that way (maybe even very little). If the work were done this way, then the Impression user would simply import the CAD file, apply the styles, and plot. But the world is not always ideal, which is why we fill our areas. Filling can be done rather quickly, but revising the work might not be as joyous an occasion. Which method is better? It just depends! Brian C. Benton is senior engineering CAD technician/designer for Heidt & Associates, Inc, Fort Myers, Florida. Brian has been working with AutoCAD since release 10 in the mechanical, structural, and civil engineering fields. He has been a detailer, drafter, designer, IT assistant, CAD software manager, protector of standards, and proverbial “Help Desk.” He can be reached at benton.brian@gmail.com 21 After the style is created and assigned to a layer, the objects on that layer will take on its properties. The speed of using layer styles comes when the CAD linework is made from closed polylines, boundaries, or regions. Closed CAD objects of these types will automatically be filled and hatched according to the style settings. The linework will be displayed according to the stroke settings of the style. Jan/Feb 2008 Figure 4: Styles Library
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