Editing Objects with AutoCAD - Section 4

CHAPTER 20: SHADOWS, DEGRADED AND CONTOURS

20.1 Shaded and degraded

In the technical drawing it is very common that there are areas of the planes that are distinguished from the others by their shading. In a sectional view of a mechanical drawing, for example, the body of a piece is filled with shading lines to highlight the cut. In a facade plan of a house, in the walls the building blocks can be simulated. In an urban engineering plan, to cite another example, the green areas can also be simulated with a certain pattern of shading, as well as the water of a lake or other patterns to signify certain types of terrains or materials.
If we had to draw such fillings, even with all the Autocad drawing and editing tools, the productivity of working would be seriously affected. Obviously, the program offers tools to automatically create shadows with different patterns already defined that solve practically any need.
To shadow an area in Autocad, we use the button with the same name in the Drawing section of the Home tab. This button is pop-up and also shows us the options to create gradient fills, or detect and create contours of closed areas. Note that when you activate it, and before designating the area to be shaded, a contextual tab appears with the different options that we can give to that shading, where we would have to start by selecting the method that we are going to use to indicate the area to be shaded.
The “Designate points” button allows us to indicate a point in the area to be filled. In this option Autocad automatically determines the contour of the area. This implies that the indicated point is inside a closed area, if the area is open, then it is not possible to do the shading and Autocad will give an error message. In turn, it is possible to indicate more than one point with this command, so that we can simultaneously shade several separate closed areas, although by default these will be dependent on each other, unless we use the button that serves to create independent hatches. In other words, if this option is not activated, any changes to the shading that we make will affect all the areas that were shaded simultaneously.

As you can deduce, the method of designating points is quite useful when the area to be filled is delimited by several objects.
The Select button is more practical when we are going to fill simple objects or closed polylines. It should be noted that with this method we can also define an area composed of several objects, just as with the previous method, but this implies pointing to all the objects that form the contour, if one is missing, we will obtain, again, the previous error message .
The second step is to select the fill pattern to be used. Autocad includes a set of pre-defined fill patterns that will make it very difficult for you not to find the one you need. Strictly speaking, shading patterns are divided into three groups, those of the ANSI standard (which is the body in charge of establishing standards in the United States), those of the famous ISO standard, which establishes international standards, not only of this, but of many aspects of the operation of industries (hence the well-known ISO 9000 quality standard) and others added by Autodesk that simulate diverse materials or symbols. The section Pattern, of the contextual tab Creation of shading, presents a preview of each of them, so it is really very easy to select the one you require for your drawing. In fact, it is important to emphasize that, thanks to the preliminary view of the result, we can continue to test the different shading patterns without applying them.
Once the pattern to be used is chosen, we must establish its properties: its color, background color, transparency, inclination and scale.

We must mention that the default scale of the shading pattern may not necessarily coincide with the scale of the drawing that we are drawing and the area to be shaded. A small scale over a large area can create a very tight shading that is not correctly reflected on the screen or printed, so it is very likely that you have to adjust that value.
In addition, although the shading is determined by the outline defined by one or several objects, the shading is made from the point of origin, or other points that we can define with the section of the same name.
For its part, the “Associative” option means that the fill will be modified when we modify the object, so, in general, it will keep this button active. Another simple option is to turn on the annotative property of hatch patterns. As we explained before, this property allows you to modify the scale of the object, in this case the pattern itself, simply by selecting the new scale from the status bar.

Remember that we mentioned that text objects, dimensions and shading patterns, among other objects, can have an activated anotative property, so that it is possible to indicate different scales according to the view of the drawing that we are using (in the model space for the design, or in some paper space to configure your layout, as we will see in chapter 30, however, you must take into account two aspects that derive from this property: 1) The shading pattern is scaled from the scale size set in the dialog box. 2) If we modify the annotative scale to modify the visualization of text objects, this modification will also affect the shading patterns, which may negatively affect their work.

On the other hand, if there are already some shaded objects and we want to use the same pattern and the same scale and angle parameters for new areas, then it is convenient to use the “Match properties” button, which allows us to copy the shading data of an area to apply it. to another

Finally, to edit shaded objects we have two paths. One of them is to use the corresponding button in the Modify section of the Home tab. This will open the old dialog that allowed us to modify the shading objects with options such as scale or angle and that you will be able to know widely in our course on Autocad 2008. The second option is much simpler, just click on some shading object, which will open the contextual tab Shading Editor, whose sections are the same as we studied here, so it is not necessary to abound in this regard.