- Chapter Objectives
- Introduction
- Using Isometric Snap
- Switching Isometric Planes
- Using COPY and Other Edit Commands
- Drawing Isometric Circles with ELLIPSE
- Drawing Text Aligned with Isometric Planes
- Drawing Ellipses in Orthographic Views
- Saving and Restoring Displays with VIEW
- Chapter Summary
- Chapter Test Questions
- Chapter Drawing Projects
This chapter is from the book
This chapter is from the book
This chapter is from the book
Drawing Ellipses in Orthographic Views
The ELLIPSE command is important not only for drawing isocircles but also for drawing true ellipses in orthographic views. There is also an option to create elliptical arcs.
An ellipse is determined by a center point and two perpendicular axes of differing lengths. In AutoCAD, these specifications can be shown in two nearly identical ways, each requiring you to show three points (see Figure 11-16). In the default method, you show two endpoints of an axis and then show half the length of the other axis, from the midpoint of the first axis out. (The midpoint of an axis is also the center of the ellipse.) The other method allows you to specify the center point of the ellipse first, then the endpoint of one axis, followed by half the length of the other axis.
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Figure 11-16 Ellipse axis and center
In preparation for this exercise, return to the standard Snap mode and Grid mode by clicking the ISODRAFT tool on the status bar to turn off the Isometric Snap mode.Your grid is returned to the standard pattern of lines, and the crosshairs are horizontal and vertical again. Notice that this does not affect the isometric bracket you have just drawn.
You briefly explore the ELLIPSE command and draw some standard ellipses.
- Ortho should be off for this exercise.
- On the Home tab, click the Ellipse drop-down menu on the Draw panel and then select the Axis, End tool, as shown in Figure 11-17.
Figure 11-17 Ellipse Axis, End tool
AutoCAD prompts:
Specify axis endpoint of ellipse or [Arc/Center]:
- Specify the axis endpoint, as shown by P1 on the ellipse at the lower left in Figure 11-18.
Figure 11-18 Drawing standard ellipses
AutoCAD prompts for the other endpoint:
Specify other endpoint of axis:
- Specify the second endpoint, as shown by P2.
As you drag the rubber band, a preview of the ellipse is updated to show the length of the other axis. Only the length of the rubber band is significant; the angle is already determined to be perpendicular to the first axis. Because of this, the third point falls on the ellipse only if the rubber band happens to be exactly perpendicular to the first axis.
As before, the following prompt allows you to specify the second axis distance or a rotation around the first axis:
Specify distance to other axis or [Rotation]:
The Rotation option is awkward to use and is not explored here; see the AutoCAD Command Reference for more information.
- Specify P3 as shown.
This point shows half the length of the other axis.
The first ellipse should now be complete. Next, you draw one by specifying the center point first, using the Center ellipse tool from the ribbon.
- Click the Center tool from the Ellipse drop-down menu on the ribbon’s Draw panel.
This uses the Center option.
AutoCAD prompts you for a center point:
Specify center of ellipse:
- Specify the center point, as shown by P1 at the middle left in Figure 11-18.
Now, you have a rubber band stretching from the center to the end of an axis and the following prompt:
Specify endpoint of axis:
- Specify an endpoint, as shown by P2 in Figure 11-18.
The prompt that follows allows you to specify the second axis distance as before, or a rotation around the first axis:
Specify distance to other axis or [Rotation]:
- Specify an axis distance, as shown by P3.
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Here again, the rubber band is significant for distance only. The point you specify falls on the ellipse only if the rubber band is stretched perpendicular to the first axis. Notice that it is not so in Figure 11-18.
Drawing Elliptical Arcs
Elliptical arcs can be drawn by trimming complete ellipses or using the ELLIPSE command’s Arc option. Using the Arc option, you first construct an ellipse using one of the two methods shown previously and then define the arc of the ellipse that you want to keep.
- Click the Elliptical Arc tool from the Ellipse drop-down menu on the ribbon’s Draw panel.
- Specify the first axis endpoint, as shown by P1 at the upper left in Figure 11-18.
- Specify the second endpoint, P2 in the figure.
- Specify P3 to indicate the second axis distance.
AutoCAD draws an ellipse as you have specified, but the object is only temporary. Now, you need to show the arc you want drawn. The two options are Parameter and Included angle. Parameter takes you into more options that allow you to specify your arc in different ways, similar to the options of the ARC command. Stick with the default option here.
- Specify P4 to indicate the angle at which the elliptical arc begins.
Move the cursor slowly along the ellipse’s preview, and you can see all the arcs that are possible, starting from this angle.
- Specify P5 to indicate the end angle and complete the ellipse.