Making the Most of Model Space

After you decide on drawing scale and sheet size, you’re ready to set up your drawing. Most drawings require a two-part setup:

1.Set up model space, where you’ll create most of your drawing.

2.Create one or more paper space layouts for plotting.

As we explain in Chapter 2, model space is the infinitely large, three-dimensional environment in which you create the “real” objects you’re drawing. You can set up your model space as described in this section; Chapter 5 introduces you to setting up your paper space layouts.

Setting your units

First, set the linear and angular units that you want to use in your new drawing. The following procedure describes how:

1.Click the Application button and then choose Units from the Drawing Utilities group.

The Drawing Units dialog box appears, as shown in Figure 4-4.

Figure 4-4: Set your units here.

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100 Part I: AutoCAD 101

2.Choose a linear unit type from the Length Type drop-down list.

Choose the type of unit representation that’s appropriate for your work. Engineering and Architectural units are displayed in feet and inches; the other types of units aren’t tied to any particular unit of measurement. You decide whether each unit represents a millimeter, centimeter, meter, inch, foot, or something else. Your choice is much simpler if you’re working in metric: Choose Decimal units.

AutoCAD can think in inches! If you’re using Engineering or Architectural units (feet and inches), AutoCAD interprets any distance or coordinate you enter as that many inches. You must use the ’ (apostrophe) character on your keyboard to indicate a number in feet instead of inches.

3.From the Length Precision drop-down list, choose the level of precision you want when AutoCAD displays coordinates and linear measurements.

The Length Precision setting controls how precisely AutoCAD displays coordinates, distances, and prompts in some dialog boxes. For example, the Coordinates section of the status bar displays the current coordinates of the crosshairs, using the current precision.

The linear and angular precision settings affect only AutoCAD’s display of coordinates, distances, and angles on the status bar, in dialog boxes, and in the command window and Dynamic Input tooltip areas. For drawings stored as DWG files, AutoCAD always uses maximum precision to store the locations and sizes of all objects that you draw, regardless of how many decimal places you choose to display in the Drawing Units dialog box. In addition, AutoCAD provides separate settings for controlling the precision of dimension text — see Chapter 14 for details.

4.Choose an angular unit type from the Angle Type drop-down list.

Decimal Degrees and Deg/Min/Sec are the most common choices.

The Clockwise check box and the Direction button provide additional angle measurement options, but you’ll rarely need to change the default settings: Unless you’re a land surveyor, measure angles counterclockwise and use east as the 0-degree direction.

5.From the Angle Precision drop-down list, choose the degree of precision you want when AutoCAD displays angular measurements.

6.In the Insertion Scale area, choose the units of measurement for this drawing.

Choose your base unit for this drawing — that is, the real-world distance represented by one AutoCAD unit.

The AutoCAD (but not the AutoCAD LT) Drawing Units dialog box includes a Lighting area where you specify the unit type to be used to measure the intensity of photometric lights. We introduce lighting as part of rendering 3D models in Chapter 23.

7.Click OK to exit the dialog box and save your settings.

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Chapter 4: Setup for Success 101

Making the drawing area snap-py (and grid-dy)

For the last three decades, AutoCAD’s grid consisted of a set of evenly spaced dots that served as a visual distance reference. You can still configure a dot grid in AutoCAD 2013, but starting with AutoCAD 2011, the default is a snazzy graph-paperlike grid made up of a network of lines.

AutoCAD’s snap feature creates a set of evenly spaced, invisible hot spots, which make the crosshairs move in nice, even increments as you specify points in the drawing. Both Grid mode and Snap mode are like the intersection points of the lines on a piece of grid paper, but the grid is simply a visual reference — it never prints — whereas Snap constrains the points that you can pick with the mouse. You can — and usually will — set grid and snap spacing to different values.

Prior to AutoCAD 2012, when Snap mode was enabled, it was on full time. This could be distracting as you moved your crosshairs around the screen — and downright annoying when you were trying to select an object that didn’t happen to fall on a snap point. You no longer have to keep toggling Snap mode on and off. It’s now engaged only when you’re using a command that asks you to specify a point. For example, when Snap is on, you can move your crosshairs freely around the screen, but when you start the LINE command, Snap mode kicks in, and your crosshairs jump to the closest snap point.

Set the grid and the snap intervals in the Drafting Settings dialog box by following these steps:

1.Right-click the Snap Mode or Grid Display button on the status bar and choose Settings.

The Drafting Settings dialog box appears with the Snap and Grid tab selected, as shown in Figure 4-5.

Figure 4-5: Get your drafting settings here!

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102 Part I: AutoCAD 101

The Snap and Grid tab has six sections, but the Snap Spacing and Grid Spacing areas within that tab are all you need to worry about for most 2D drafting work.

2.Select the Snap On check box to turn on Snap mode.

This action enables default snaps half a unit apart (ten units apart if you’re working with the default metric template).

AutoCAD usually has several ways of doing things. You can also click the Snap Mode button on the status bar to toggle snap on and off; the same goes for the Grid Display button and the grid setting. Or you could use the function keys: F7 toggles the grid off and on, and F9 does the same for Snap mode.

3.Enter the snap interval you want in the Snap X Spacing box.

Use the information in the sections preceding this procedure to decide on a reasonable snap spacing.

If the Equal X and Y Spacing check box is selected, the Y spacing changes automatically to equal the X spacing, which is almost always what you want. Deselect the check box if you want to specify unequal snap spacing.

4.Select the Grid On check box to turn on the grid.

5.Enter the desired grid spacing in the Grid X Spacing box.

Use the information in the sections preceding this procedure to decide on a reasonable grid spacing.

As with snap spacing, if the Equal X and Y Spacing check box is selected, the Y spacing automatically changes to equal the X spacing. Again, you usually want to leave it that way.

X measures horizontal distance; Y measures vertical distance. The AutoCAD drawing area normally shows an X and Y icon in case you forget.

If you’re an old AutoCAD hand and find the graph-paper grid too obtrusive, select the Display Dotted Grid In 2D Model Space check box in the Grid Style area to switch to the old-style rows and columns of dots.

6.Specify additional grid display options in the Grid Behavior area.

If you select the Adaptive Grid check box, AutoCAD changes the density or spacing of the grid lines or dots as you zoom in and out. If you also select Allow Subdivision Below Grid Spacing, the spacing can go lower than what you’ve set, and it may go higher if you’re zoomed a long

way out of your drawing. (If it didn’t, you couldn’t see your drawing for the grid!)

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