Читать книгу Beginning AutoCAD 2018 - Cheryl R. Shrock - Страница 12
ОглавлениеLEARNING OBJECTIVES
After completing this lesson, you will be able to:
1. Understand Object Snap.
2. Use Running Object Snap.
3. Use the Zoom options to view the Drawing.
4. Change the Drawing Limits.
5. Select the Units of Measurement and Precision.
In Lesson 3 you learned about Increment Snap. Increment Snap enables the cursor to move in an incremental movement. So you could say your cursor is “snapping to increments” preset by you.
Now you will learn about Object Snap. If Increment Snap snaps to increments, what do you think Object Snap snaps to? That’s right; “objects”. Object Snap enables you to snap to “objects” in very specific and accurate locations on the objects.
For example, the endpoint of a line or the center of a circle.
How to select from the Object Snap Menu
1. You must select a command, such as Line, before you can select Object Snap.
2. While holding down the shift key, press the right mouse button. The menu shown below should appear.
3. Highlight and press the left mouse button to select an Object Snap.
The following Object Snaps will be discussed in this Lesson:
Endpoint, Midpoint, Intersection, Center, Geometric Center, Quadrant, Tangent and Perpendicular. Refer to their descriptions on the next page.
The remaining Object Snaps will be discussed in future lessons.
Object Snap Definitions
Object Snap is used when AutoCAD prompts you to place an object. Object Snap allows you to place objects very accurately.
A step-by-step example of “How to use Object Snap” is shown on the next page.
Note: You may type the 3 bold letters shown rather than select from the menu.
| ENDpoint | Snaps to the closest endpoint of a Line, Arc or polygon segment. Place the cursor on the object close to the end and the cursor will snap like a magnet to the end of the line. |
| MIDpoint | Snaps to the middle of a Line, Arc or Polygon segment. Place the cursor anywhere on the object and the cursor will snap like a magnet to the midpoint of the line. |
| INTersection | Snaps to the intersections of any two objects. Place the cursor directly on top of the intersection or select one object and then the other and Autocad will locate the intersection. |
| CENter | Snaps to the center of an Arc, Circle or Donut. Place the cursor on the object, or at the approximate center location and the cursor will snap like a magnet to the center. |
| Geometric CEnter | Snaps to the centroid of any closed polylines and splines. Place the cursor anywhere on the object and the cursor will snap to the centroid of any closed polyline or spline. |
| QUAdrant | Snaps to a 12:00, 3:00, 6:00 or 9:00 o’clock location on a circle or ellipse. Place the cursor on the circle near the desired quadrant location and the cursor will snap to the closest quadrant. |
| TANgent | Calculates the tangent point of an Arc or Circle. Place the cursor on the object as near as possible to the expected tangent point. |
| PERpendicular | Snaps to a point perpendicular to the object selected. Place the cursor anywhere on the object then pull the cursor away from object and press the left mouse button. |
How to Use Object Snap
The following is an example of attaching a line segment to previously drawn vertical lines. The new line will start from the upper endpoint, to the midpoint, to the lower endpoint.
1. Turn off SnapMode, OrthoMode and Object Snap on the Status Bar. (Gray is off)
2. Select the Line command.
3. Draw two vertical lines as shown below (they don’t have to be perfectly straight).
4. Select the Line command again.
5. Hold the shift key down and press the right mouse button.
6. Select the Object Snap Endpoint from the Object Snap Menu.
7. Place the cursor close to the upper endpoint of the left hand line.
The cursor should snap to the end of the line like a magnet. A little square and an “Endpoint” tooltip are displayed.
8. Press the left mouse button to attach the new line to the upper endpoint of the previously drawn vertical line. (Do not end the Line command yet.)
9. Now hold the shift key down and press the right mouse button and select the Midpoint Object Snap option.
10. Move the cursor to approximately the middle of the right hand vertical line.
The cursor should snap to the midpoint of the line like a magnet. A little triangle with a “Midpoint” tool tip are displayed.
11. Press the left mouse button to attach the new line to the midpoint of the previously drawn vertical line. (Do not end the Line command yet.)
12. Now hold the shift key down and press the right mouse button and select the Object Snap Endpoint again.
13. Move the cursor close to the lower endpoint of the left hand vertical line.
The cursor should snap to the end of the line like a magnet. A little square and a tooltip are displayed.
14. Press the left mouse button to attach the new line to the endpoint of the previously drawn vertical line.
15. Stop the Line command and disconnect by pressing <enter>.
Selecting Object Snap is not difficult but AutoCAD has provided you with an additional method to increase your efficiency by allowing you to preset frequently used Object Snap options. This method is called Running Object Snap.
When Running Object Snap is active the cursor will automatically snap to any preset Object Snap locations thus eliminating the necessity of invoking the Object Snap Menu for each locations.
First you must set the running Object Snaps, and second, you must turn on the Running Object Snap option.
Setting Running Object Snap
1. Select the Running Object Snap dialog box using one of the following:
Keyboard = DS <enter<
or
Status Bar = Left Click on Object Snap button down arrow and select Object Snap Settings.
2. Select the Object Snap tab.
3. Select the Object Snaps desired.
(In the example below Object Snap Endpoint, Midpoint and Intersection have been selected.
4. Select the OK button.
5. Turn on the Object Snap button on the Status Bar. (Blue is on)
6. Now try drawing the line from the endpoint to the midpoint again but this time do not select the “Object Snap Menu”. Just move the cursor close to the endpoint and the cursor will automatically snap to the end of the line.
7. Move the cursor to approximately the middle of the right hand vertical line and the cursor will automatically snap to the midpoint of the line.
8. Move the cursor close to the lower endpoint of the left hand vertical line and the cursor will automatically snap to the lower endpoint of the left line.
Running Object Snap is very handy but remember do not select more than 3 or 4 at a time. The selections will fight each other and you may end up snapping to a location that you did not want.
If you wish to snap to a location that is not preset merely select the Object Snap Menu, as shown on page 4-2, and select the one you want. Running Object Snap and Object Snap work together very well but it may take a little practice.
The Zoom command is used to move closer to or farther away from an object. This is called Zooming In and Out.
The Zoom commands are located on the Navigate panel of the View tab and are off by default. Select the View tab then right-click on any panel and select Show Panels, activate the Navigate panel. (To show panels refer to page 1-11.)
1. Select the Zoom command by using the following:
Ribbon = View Tab / Navigate Panel
2. Select the down arrow to display all of the selections.
You may also select the Zoom commands using one of the following:
Right click and select Zoom from the Shortcut Menu. (Refer to Intro-5 for “right-click” settings.)
Keyboard = Z <enter>. Select from the options listed..
How to use Zoom / Window
1. Select Zoom / Window (Refer to previous page).
2. Create a window around the objects you want to enlarge. (Creating a “window” is a similar process to drawing a rectangle. It requires a first corner and then diagonal corner.)
How to return to Original View
1. Type: Z <enter> A <enter> (This is a shortcut for Zoom / All).
When drawing with a computer, you must “set up your drawing area” just as you would on your drawing board if you were drawing with pencil and paper. You must decide what size paper you will need, what Units of measurement you will use (feet and inches or decimals, etc) and how precise you need to be. In CAD these decisions are called “Setting the Drawing Limits, Units and Precision”.
Drawing Limits
Consider the drawing limits as the size of the paper you will be drawing on. You will first be asked to define where the lower left corner should be placed, then the upper right corner, similar to drawing a Rectangle. An 11” × 8.5” or 297 mm × 210 mm piece of paper would have a lower left corner of and an upper right corner of 11, 8.5, or 297, 210. (11 or 297 is the horizontal measurement X-axis, and 8.5 or 210 is the vertical measurement Y-axis.)
How to Set the Drawing Limits
Example:
1. Start a New drawing using either the inch-helper.dwt or the metric-helper.dwt (Refer to page 2-6).
2. Select the Drawing Limits command by typing: Limits and then press <enter>.
3. The following prompt will appear:
Command: ‘_limits
Reset Model space limits:
Specify lower left corner or [ON/OFF] <0.0000,0.0000>:
4. Type the X,Y coordinates 0,0 <enter> for the new lower left corner location of your piece of paper .
5. The following prompt will appear:
Specify upper right corner <12.0000, 9.000:>0
6. Type the X,Y coordinates 36,24 <enter> if you are using the inch template, or 914.4,609.6 <enter> if you are using the metric template, for the new upper right corner of your piece of paper. Make sure you separate the two figures with a comma.
Note: Visually the screen has not changed. Do the next step and it will.
7. This next step is very important:
Type Z <enter> A <enter> to make the screen display the new drawing limits. (This is the shortcut for Zoom / All. Refer to page 4-9)
