IN THIS CHAPTER

Placing hatch patterns in drawings

Applying annotative hatch patterns

Choosing hatch boundaries

Using predefined and user-defined hatch patterns

Editing hatches

When you need to fill closed areas of drawings with special patterns of lines (crosshatches, or simply hatches) or fill them with solid colors, this is your chapter. If you were hoping to hatch a plot or plot a hatch, see Chapter 16. If you want to hatch an egg, look at Raising Chickens For Dummies, by Kimberly Willis and Robert T. Ludlow (Wiley).

A hatch in AutoCAD is an object that fills an area. Its appearance is dictated by the pattern or fill color assigned to it. It is associated with the objects that bound the area — typically, lines, polylines, and arcs make up the boundary, much like borders of a country. When you move or stretch the boundary, AutoCAD normally updates the hatch to match the moved or resized area.

Drafters often use hatches to represent the types of material from which the objects they are designing are made or filled, such as metal, insulation, or concrete. In other cases, hatch patterns help emphasize and clarify particular elements in drawings — for example, the location of walls in a building plan or swampy areas on a map so that you know where to avoid building the road.

Figure 15-1 shows an example of using hatches to specify a concrete footing. The four patterns indicate materials to be used; from top to bottom, they are concrete, gravel, sand, and soil. In mechanical design, hatches are used to show which faces are cut in cross sections, as well as to indicate the material.

Creating Hatches

This section gives you a jump-start on the basic process AutoCAD uses to create hatches and shows you how easy it is. I also cover many of the options included on the Hatch Creation contextual tab on the Ribbon, shown in Figure 15-2, and how to edit existing hatched areas.

Follow these steps to hatch an enclosed area by using the pick-points method of showing the area to be hatched:

1. Start a new drawing, using the acad.dwt template for imperial units or acadISO.dwt for metric units.

   Draw a circle with a radius of 5 units (imperial) or 50 units (metric). Draw a second circle inside the first with a radius of 2 units (imperial) or 20 units (metric).

2. Start the Hatch command by typing H and pressing Enter or by clicking the Hatch button in the Draw panel of the Home tab on the Ribbon.

   The Hatch Creation contextual tab on the Ribbon appears, as shown in Figure 15-2. Ignore it for now.

3. Move the cursor on the screen.

   As the cursor moves within any enclosed area in the drawing, a preview of the pattern shows you how the final hatch will look after you pick a point inside that particular area. Starting from outside the larger circle, move the cursor into the space between circles, and then into the inner circle, and then back into the space between circles, noting how the quick preview shows the area to be hatched.

4. Change some hatch options.

   The quick preview updates also as you select different patterns and change values in the Hatch Ribbon tab. Try different patterns. The three little arrows along the right side of the Pattern panel scroll through the different patterns that are available. My favorite pattern is Escher.

5. Pick a point in the region between the circles and then press Enter or the spacebar.

6. Click the Close Hatch Editor button to exit the command.

   Congratulations — in only a few seconds, you’ve done something that would have taken an hour or more in the days of pencil and paper!

7. Change the diameter of the outer circle:
   1. Click the outer circle and then click and drag one of its four outer grips to change the diameter of the circle. The hatch pattern updates to match. This behavior, which is due to AutoCAD associating the pattern to its boundaries (in this case the two circles), is known as associative hatching.
   2. Click the inner circle, and then click and drag its center grip to move it outside the larger circle. The hole in the pattern of the larger circle fills in and the smaller circle gets filled with hatching.
   3. Click the smaller circle and then click and drag its center grip to move it back inside the larger circle. The smaller circle loses its hatch and reverts to cutting a hole in the hatch of the larger circle.

When working with hatches, keep these tips in mind:

• Place the hatches on a dedicated layer or layers. You can then easily turn hatches off, which is useful for making drawings clearer to read and printing draft plots more quickly. See “Hatching Its Own Layer.”
• Always use the Continuous line type for hatch layers. Most hatch patterns display patterns of lines generated by the hatch process. If you place hatches on a layer with a noncontinuous line type, the Hatch command tries to create each of its own noncontinuous line segments from noncontinuous lines and the hatch process looks a little bizarre.
• Modify each hatch separately. By default, when you select two or more separate, closed areas, the areas are hatched as a single object. Later, when you edit one hatched area, all areas in the original set update. A good example of this is the cross-section of a complex mechanical part. When you want to apply a lot of hatches at once, but be able to modify each hatched area on its own, choose Create Separate Hatches on the Options slideout panel.
• Set the Draw Order to specify whether the hatch objects are in front of or behind the hatch boundary or other drawing objects, as shown in Figure 15-3. By default, they’re sent behind their boundary, which is typically what you want. If a hatch is a different color from its boundary and if it’s in front of its boundary, the ends of the hatch lines produce an unwanted dotted effect along the boundary.

Hatching Its Own Layer

Starting with AutoCAD 2017, you can set up drawings so that hatches are placed on a layer of their own, automatically. Follow these steps:

1. Start the LAyer command.

   To do so, click the Layer Properties button on the Layers panel of the Home tab.

2. Create a new layer.

   Give it a suitable name, such as Hatch, and assign it a color. I discuss layers in Chapter 9.

3. Start the Hatch command.

   Type H and press Enter or click the Hatch button on the Draw panel of the Home tab.

4. Select your Hatch layer.

   Click the down arrow at the bottom of the Properties tab to see the slideout panel. In the Hatch Layer Override drop-down list that appears, change the layer from Use Current to the new layer you created.

5. Close the Hatch Creation tab by clicking the Close Hatch Creation button.

   That’s it! From now on, whenever you create a hatch pattern in this drawing it will automatically land on the Hatch layer, regardless of which layer is currently active. Remember to add this layer to your template drawings; you can do this by using the HpLayer system variable.

Create and set your default Hatch layer in your template drawing. Then any new drawings you create from your template will automatically have the Hatch layer predefined. I discuss templates in Chapter 4.

Using the Hatches Tab

Now that you know how easily you can hatch areas, you can explore the main options in the contextual Hatch Creation tab of the Ribbon. Any time you start the Hatch command, you see the Hatch Creation tab. (Refer to Figure 15-2.) If you double-click an existing hatch, you see the Hatch Editor tab instead, but the two tabs are virtually identical.

Working from left to right, the Hatch Creation tab contains these options:

• Boundaries: The easiest, most intuitive, and most common way to define the boundary of a hatch is to simply pick inside a region. AutoCAD searches for objects nearest the pick point that would enclose an area, and then highlights them in blue. If you pick multiple regions in one run of the Hatch command, each region is hatched, and the result is one big hatch object, even when parts look disconnected. If you edit the properties of any region later, then connected hatches are updated. This strategy is commonly used when hatching the cut faces of a cross section; all faces common to a single item automatically maintain matching hatch properties.

  Choose Create Separate Hatches on the Options slideout panel when you want to modify each hatched area independently.

  You can also select an area to hatch by picking objects that could define the boundary, but you must select enough objects to define a fully enclosed region.

  Starting with AutoCAD 2014, when you’re picking in multiple bounded areas or selecting individual objects, the Hatch command includes an Undo option in case you accidentally pick the wrong area or object.

• Island Detection: In the section “Creating Hatches,” you can see how the hatch pattern behaves when you select the region between the circles; it doesn’t hatch the inner circle. This is island detection. If you select specific objects for the boundary, island detection is turned off. If island detection is off and you select only the outer circle, the hatches run right over the inner circle. To learn more about island detection, consult the Help system.

  No matter which selection method you choose, the boundary must usually be airtight. Boundary objects can overlap, but they can’t have leaks — not even microscopic ones. Technically, a fuzz factor can be set in AutoCAD to allow for tiny leaks. However, I don’t tell you how to set a fuzz factor because it defeats the purpose of drawing with precision.

  Whenever you see the error message A Closed Boundary Could Not Be Determined, you need to adjust lines and other boundary objects so that they define a fully airtight boundary. The Hatch command displays red circles at gaps in the not-quite-enclosed area you want to hatch. Even when it doesn’t fix the gaps, it shows you where you should fix them. Sometimes, you can use the Fillet command with a 0 (zero) fillet radius or the Join command to force two lines to meet exactly,. Another possibility is to use grip editing to align one endpoint precisely with another with the assistance of Object Snap (see Chapter 11).

• Pattern: The scroll arrows at the right edge of the Pattern panel give access to the 82 predefined hatch patterns, including nine solid and gradient fills that ship with AutoCAD. You can define two or three colors for the gradient fills, making them suitable for simulating curved surfaces or sunsets in the desert.

  Hatch patterns are defined by external files named acad.pat or acadlt.pat in imperial units, and acadiso.pat or acadltiso.pat in metric. Each file includes the definitions for all patterns. You can create your own hatch patterns; the Customization Guide in the online Help system explains how. You can buy libraries of custom hatch patterns. Any pattern not defined in acad.pat or acadiso.pat is referred to as a custom pattern, but you must be careful when using them. Because they’re external files, they must be available to AutoCAD whenever anyone opens a drawing containing them. If you send the drawing to someone else, you must also send the pattern definition file(s), which can have copyright issues if you've purchased them.

  Autodesk created a set of hatch patterns whose names begin with the characters AR- (that’s a hyphen at the end) for use in architectural drawings. Unlike non-AR patterns, they do represent real objects such as brick and roof shakes. The AR patterns were designed with a final hatch scale of 1.0 in mind, but in some cases you have to adjust up or down to achieve a suitable scale.

• Properties: The Properties panel contains buttons for nearly a dozen properties that can be assigned to hatches. I talk about the most important ones here. They are identified by their default values — your results may differ:
  • Pattern: See the Pattern panel.
  • By Layer: This button refers to the color of the hatch lines and should nearly always be set to ByLayer, which is what the current general color override should be.
  • None: This button refers to the background color, which can be useful when using hatching to portray actual objects. For example, a brick pattern can have black hatch lines with a red background so that the hatched region looks like red bricks, as shown in Figure 15-4.
  • Hatch Transparency: The options for this button range from 0 percent (opaque) to 90 percent (nearly transparent). Sometimes a faded hatch patterns helps reduce its visual effect.
  • Angle: Hatch patterns can be rotated at any angle you want. For example, standard practice in mechanical design is to hatch cut faces in cross sections of assemblies, usually with pattern ANSI31, and then to adjust the angle of each pattern to help distinguish one from its adjoining one. Note that some patterns (the ANSI series, in particular) usually have an initial 45-degree rotation built in.
  • 1,0000: Ah, here’s the big one (pun intended), scale. I cover it in more detail in the “Scaling Hatches” section later in this chapter.
• Set Origin: AutoCAD typically creates hatched areas by having them radiate outward from the origin (0,0 of the drawing, by default), effectively turning hatches on and off as they encounter boundaries. This behavior can, however, cause problems with certain real-object patterns. You wouldn’t want a brick wall to start with 3/17 of a brick, so the Origin option lets you snap to an exact point, such as the lower-left corner of a wall. See Figure 15-4. You may also want to check out Chapter 9’s reference to the need for a brick layer.
• Options: This one has many suboptions, but these three are the most important:
  • Associative: By default, hatches are associative to their boundaries. One knows about the other, which explains what happens when you change and move boundary objects after hatching is applied.
  • Annotative: Like text (described in Chapter 13) and dimensions (described in Chapter 14), hatches must be scaled properly to match the drawing scale. I cover this topic in more detail in the later section “Scaling Hatches.”
  • Match properties: This function lets you select an existing hatch object and then copy its properties onto another hatch object, just like the Format Painter in many Windows applications. I talk about Format Painter under “Adding style.”
• Close Hatch Creation: Surprise! This option closes the Hatch tab.

Scaling Hatches

Hatches are annotation objects, just like text (see Chapter 13) and dimensions (see Chapter 14). Their size is independent of the geometry in the drawing. They impart important information and so must be clearly visible on the screen and on the printed page.

Like text and dimensions, hatches need to be scaled to suit the final drawing scale. Start with the common ANSI31 pattern. As defined, it produces parallel lines spaced 1/8″ apart. So far, so good — but what if you’re applying the cross section to a large part, such as the 10′ boom on a backhoe? Remember that you always draw at full size and then scale to suit the plot.

If you were to apply hatches at the nominal 1:1 scale and then plot at, say, 1:10 to fit the big boom on a small sheet of paper, the 1/8″ hatch spacing becomes a tiny 0.0125-inch spacing, which is plotted effectively as a solid fill. The information imparted by the pattern is lost. So, as with text and dimensions in this drawing, you apply to the hatches a scale factor, say 10. The hatch lines in the drawing file then are bumped up to 1.25 inches apart, which scales down to the correct 1/8″ apart when plotted. I discuss scale factors also in Chapter 4.

Annotative versus non-annotative

Figure 15-5 illustrates two versions of the same drawing, one half dressed up with annotative hatch patterns and the other with non-annotative hatch patterns. As shown by the annotation scales displayed on the drawings’ status bars, annotative hatches change their scales automatically, whereas the size of the non-annotative hatches remains unchanged.

Chapter 14 shows another example: The hatches in both views are the same object, but because the viewports have different scales, the hatches adjust accordingly.

Before annotative hatches first appeared in AutoCAD 2008, the only way to create the effect in both drawings was to create separate layers (one for each hatch scale), hatch the object twice, and then freeze or thaw layers as needed.

Pushing the Boundaries of Hatch

In the remainder of this chapter, you discover how to refine hatch techniques. I describe how to copy existing hatches, take advantage of additional options in the Hatch and Gradient dialog box (which offers a bit more control than the Hatch Creation contextual tab), and choose more complicated hatch boundaries.

Hatches from scratch

You can use predefined, custom, and user-defined hatch patterns. Most of the time, you’ll choose predefined hatch patterns, unless some generous soul did the hard work of writing a custom pattern for you. On the other hand, I haven’t employed a user-defined pattern in over 25 years of using AutoCAD because these hatches consist solely of continuous lines: All you can define are the spacing, the rotation angle, and whether the lines are cross-hatched. All this already exists in the set of predefined patterns.

An alternative to using the Ribbon to define patterns is the Hatch and Gradient dialog box, as shown in Figure 15-6. You don’t see the hatch object updating as you change settings (as you do with the Ribbon), but the dialog box gives you more control over what you end up with. To display the Hatch and Gradient dialog box, click the dialog box launcher (the tiny arrow at the right end of the Options panel on the Hatch Creation tab of the Ribbon).

By default, the right third of the Hatch and Gradient dialog box is hidden; to see additional hatch options at the right side of the dialog box (as shown in Figure 15-6), click the More Options arrow beside the Help button.

Pick a pattern — any pattern: Predefined hatch patterns

Using predefined hatch patterns in the Hatch and Gradient dialog box requires two steps. First, select Predefined from the Type drop-down list at the top of the dialog box. Then specify the pattern you want in one of two ways:

• Pattern drop-down list: If you know the name of the hatch pattern, select it from the Pattern drop-down list. The list is alphabetical, except SOLID (that is, a solid fill), which appears at the beginning.
• Pattern button: If you don’t know the pattern name or you prefer the visual approach, click the … button to display the Hatch Pattern Palette dialog box with its pattern previews and names. The dialog box groups patterns in tabs: ANSI, ISO, Other Predefined, and Custom.

Figure 15-7 shows all predefined hatch patterns included with AutoCAD, covering everything from dirt to Escher to stars.

When is a pattern not a pattern? When it’s a solid fill

AutoCAD treats filling an area with a solid color as a type of hatch. Simply choose SOLID from the top of the Pattern drop-down list. You also see several gradient-fill options, where one color gradually changes to another. The bottom of Figure 15-7 shows examples of gradient fills.

Like any other object, a solid hatch takes on the current layer’s color when you maintain (as you should) the color as ByLayer. It takes on the current object color override when people who don’t know what they’re doing alter the drawing. Therefore, check whether the current object layer and color are set appropriately before you use the Solid hatches option. (See Chapter 9 for details.)

Here’s looking through you, kid

The transparency object property in AutoCAD is probably most useful (in 2D, anyway) when applied to solid fills. You can use transparent solid fills to demarcate (distinguish) areas on architectural floor plans or aerial photographs of project sites, while letting text and symbols show clearly. In addition to ByLayer and Solid settings, make sure that the current object or layer transparency is set correctly, too.

Editing Hatch Objects

Editing an existing hatch pattern is easy after you’re familiar with the Hatch Creation tab on the Ribbon. Follow these steps:

1. Select the hatch object.

   AutoCAD opens the Hatch Editor contextual tab on the Ribbon and displays the hatch object’s current settings.

2. Make any changes you want and watch the real-time preview as you do. When you’re happy, click Close Hatch Editor to retain the changes.

Alternatively, you can use the Properties palette or the Quick Properties palette (described in Chapter 9) to make most of the changes to existing hatch patterns. AutoCAD always displays the Hatch Editor tab when you click a hatch object, and it opens the Quick Properties palette when the QP button is turned on. The Properties palette is especially useful for changing several hatches at a time.

Simple grip-editing is also available. Select a hatch and then hover the cursor over the round, blue center grip. A contextual menu opens to give you quick access to changing the hatch origin, angle, and scale. Don’t be misled by the Stretch option on the context menu, though: It only moves the hatch, and then it loses its associativity to its boundary.

Here are a few other hatch tips:

• To make one hatch look like another (without even opening the Hatch Editor tab): Click the Match Properties button in the Clipboard panel on the Home tab of the Ribbon.
• To mirror drawing geometry that includes hatches without mirroring the hatch angle: Set the MIRRHATCH system variable to 0 to retain the hatch pattern or to 1 to mirror the pattern. This tip can be quite useful when creating drawings of symmetrical objects. Model one half, apply the hatch, and then use the MIrror command (see Chapter 11) to get the other half. The hatch angle remains consistent on both sides of the mirror line if MIRRHATCH is 0.
• To find the area of any hatch object: Simply select the hatch object and then open the Properties palette. The area is listed in the Geometry section, near the bottom of the palette.

Don’t go overboard with hatches. Their purpose is to clarify, not to overwhelm, other geometry in the drawing. If your plots comprise a patchwork of hatch patterns, it’s time to simplify.

Always apply hatches last, if you can. The Hatch command is smart enough to recognize text and dimensions that fall within the hatched area, and so treats them like sterile eggs and automatically omits hatch zones around them. If you forget, or if you need to add a note later in a hatched area, apply background masking to the text, as discussed in Chapter 13.