Get to the point with AutoCAD 2000's Polar function31 Aug, 2000 By: Bill Fane
The British have a traditional saying on the passing of a monarch: The king is dead. Long live the king! The time has come to acknowledge that Ortho is dead. Long live Ortho! I have taught AutoCAD for many years, and I never thought Id tell my students that they dont need to use Ortho. Well, Ive told them twice in the last few yearswhen Mechanical Desktop was introduced, and now with AutoCAD 2000. Ortho is nice as far as it goes. It ensures that a pickpoint is either horizontal or vertical from the previous point. It has a multitude of uses, not limited to the drawing of lines. You can also use it during operations such as Move, Mirror, and Copy.
On the other hand, Ortho has a couple of limitations. You must turn it on when you need it and off when you dont, and it works only at right angles. To operate at anything other than horizontal and vertical, you need to change your UCS (user coordinate system) or use the Rotate option of the Snap command.
How would you like an Ortho function that works at any angle and is smart enough to sense when you want it on or off? Take a peek at the Polar function in AutoCAD 2000.
Figure 1 shows a simple line drawn in AutoCAD 2000. It starts at the lower left, followed by two To Point picks. I am now ready to select the next point.
|Figure 1. Draw a simple line in AutoCAD 2000.|
|Figure 2. AutoCAD 2000 enters Ortho mode to propose the next point based on where you move your cursor.|
Now take a look at figure 2. I moved the cursor down to be almost horizontal to the previous point, and AutoCAD automatically shifted into Ortho mode! Look closelyits not really Ortho, it just looks like it. AutoCAD proposed the horizontal line and signaled a Polar operation by showing the extension of the line as a dashed line. The normal cursor appears above the line, and the small X indicates the proposed pick point. A yellow tool tip shows that this is a polar operation. It also shows the distance and angle from the previous point.
I havent actually picked the point yet. If I move the cursor away from almost horizontal, everything automatically reverts to normal mode. If I move to almost vertical above the last point, polar kicks in again, this time vertically.
You can toggle polar mode on and off, even in the middle of a command, by selecting the Polar button in the status bar or by pressing <F10> on the keyboard.
wait! Theres more!
Right-click on the status-bar Polar button, then click on Settings. Up comes the Drafting Settings dialog box of figure 3. Now the fun really starts.
|Figure 3. Drafting Settings dialog box lets you set angles and options to fine-tune the Polar command.|
Take a look at Polar Angle Settings in the upper left corner of the box. Click on the down arrow beside the Increment angle box to see a pull-down list of eight angles. These include common values such as 45, 30, and so on. Click on 45, then OK. You now have Ortho locks at every 45° increment. If you dont like the offered selection, you can type in any value you want, providing it divides evenly into 360.
No more rotating your snap setting or changing the UCS every time you want to Ortho to a different angle.
I am designing a building wherein one wing is at an angle of 37.3° to another. That doesnt divide evenly into 360.
Click on the Additional Angles button of the Drafting Settings dialog box. This activates the larger rectangle below it.
|Figure 4. You can enter as many custom Polar angles as you want.|
Click on the New button. AutoCAD invites you to enter your new value. This activates only a single angle. To make Polar align to a four-way Ortho setting based on this angle, you must click New three more times and manually enter the additional angles, as shown in figure 4. You can also toggle Additional Angles on and off without losing their settings.
Now look at the Polar Angle Measurement area in the lower right corner of the main Polar tracking box.
By default, the polar angles are absolute in that they are relative to the current coordinate system. Guess what happens when you click on Relative to Last Segment? Right! When you return to your drawing and select two points, your Polar angle settings rotate to match, as if you had switched to a different UCS.
On the other hand, you dont need to create a polar angle if you want to use it only once. Whenever a command asks for a point, you can type in a specific angle preceded by a left angle bracket (<). For example, enter <142 to set a polar tracking override of 142°, then select or specify the distance.
Direct Distance Entry works with Polar, so once you establish a direction, simply type in a desired value to get an exact distance in that direction.
|Figure 5. Direct distance entry works with Polar features.|
Now right-click on the Snap button of the status bar. Click on Settings and the Drafting Settings dialog box appears with the Snap and Grid tab active, as in figure 5.
Note the Polar Spacing entry in the lower left corner. Also note that the Polar Snap button in the lower left corner and the Snap On button in the upper right are selected.
Figure 6 shows the result of these settings. As I draw, Polar works as usual except that all my line segments automatically snap to be multiples of 1.000 units long. This is exactly the same as the normal Snap operation except it works at the polar angles.
Polar provides two really magic features. First, it works with any command that asks for a second point. You are not limited to drawing linesyou can use it within commands such as Copy, Move, Mirror, Array, and so on.
Figure 6. Polar and Snap work in concert.
Second, it is totally transparent. You can turn Polar on and off and even change the settings in the middle of any other command.
Polar kicks in when you are almost on the polar angle. How close is almost?
Polar is controlled by your Aperture setting. The smaller your aperture and/or the further away you are from the current point, the closer you must get before it activates.
My polar angle setting is 22.5°, but the tool tip shows only integer angles. What happened to the half degree?
Nothing. The angle precision setting in the Units command sets the tool tip display precision. AutoCAD uses the angle value you entered, regardless of the display precision you set.
What happened to Ortho?
Nothing. Its still there, but it cant coexist with Polar. If you turn one on, it automatically turns the other off.
Come back next month when I tell you all about the new AutoCAD 2000 object tracking enhancements and how they work with Polar.
now for something completely different
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