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Inside AutoCAD 14

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- 15 -

Paper Space


by Bill Burchard

Paper space is a very powerful feature of AutoCAD. It has the capability to plot a model space drawing without cluttering the drawing with objects only needed for plotting purposes, such as title blocks and sheet borders. You can create a standard size sheet border in paper space and plot it at 1:1 scale. By creating multiple viewports of the model space objects, you can view the objects from different angles. After the views are established, you can move and arrange the viewports in paper space to any necessary position inside the sheet border. All this can be accomplished without compromising the purity of the model space drawing by allowing the project's design model to exist separately from objects only needed for plotting sheets. By using paper space properly, you can quickly and easily design the sheet layouts needed to plot model space objects.

This chapter discusses the following subjects:

Understanding the Basics of Paper Space

To maintain a high level of productivity in AutoCAD, properly using model space and paper space is important. This means understanding why you should use paper space and when to use it versus model space. By understanding the circumstances in which the two spaces were intended to be used, you can reduce object editing time and increase productivity.

Why Use Paper Space?

Paper space was developed to make it easy for CAD technicians to create paper plots of CAD drawings. Prior to paper space, model space would be burdened with objects that were specifically needed for plotted sheets. Items such as borders, scales, title blocks, and revision blocks have nothing to do with the actual model; they are only needed on the plotted sheets.

Before the introduction of paper space, problems arose when plotting large model space objects; multiple sheets were needed to show them in their entirety. With multiple sheets came the dilemma of showing only those portions of the model space objects that appeared on a specific sheet. How do you trim the model space objects that extend beyond the sheet's borders without compromising the integrity of the drawing? These were common problems CAD technicians had to deal with.

For example, figure 15.1 shows a preliminary layout for a set of street improvement plans. Notice that the street and underlying contours appear in each sheet's border and title block, which is unacceptable. By using paper space viewports, you can easily remove the model space drawing from areas in which it should not appear.

Figure 15.1 A common problem of plotting sheets from model space is removing the objects that appear in the sheet's borders and title block.

Paper space solved many of these plotting problems by providing a special environment just for plotting purposes. CAD technicians could easily concentrate on the project's design in model space and then change to paper space to create the views necessary to display just the portions of the project needed for plotting, as shown in figure 15.2.

Figure 15.2 Paper space makes it easy to remove model space objects that appear in the sheet's borders and title block.

Understanding the TILEMODE System Variable

When talking about paper space and model space viewports, it is necessary to understand the role of the TILEMODE system variable in their creation. Specifically, this variable controls what type of viewport can be created: tiled or untiled.

Tiled viewports are created when the TILEMODE system variable is set to 1 (ON). Untiled--or floating--viewports are created when the TILEMODE system variable is set to 0 (OFF). Tiled viewports are created in model space by using the VPORTS command. Floating viewports are created in paper space by using the MVIEW command.


TIP: To quickly switch TILEMODE on and off, double-click the TILE button on the status bar at the bottom of your screen. When the button is grayed, TILEMODE is off. When it is solid, TILEMODE is on.

Tiled viewports, as the name implies, appear as tiles on the screen. They subdivide the original model space viewport (which is a single tiled viewport) into multiple viewports, as shown in figure 15.3. They are fixed and cannot be moved. They never overlap and their edges always lie adjacent to the surrounding viewports. The currently selected tile can be further divided into more tiles or joined with another tiled viewport to create a new larger one.

Figure 15.3 Model space viewports subdivide the screen into smaller tiled viewports. They cannot overlap.

Floating viewports neither subdivide the screen nor remain fixed. They can, however, be copied, resized, and moved, just like any other AutoCAD object. They can even overlap each other, as shown in figure 15.4.

Figure 15.4 Paper space viewports can be copied and resized, and can overlap.

Understanding Limitations of Paper Space versus Model Space

Understanding the limitations of working in paper space is important. Because paper space is intended to make creating plots easier, certain commands that are available in model space don't work in paper space.

For example, paper space is intended to be a two-dimensional environment. Even so, AutoCAD enables you to create three-dimensional objects such as 3D polylines, solids, and extruded objects in paper space. You can even change the position and rotation of the paper space UCS. The limitation is that you cannot change the view to look at three-dimensional objects from different perspectives. Commands such as PLAN and DDVPOINT are disabled in paper space.

In model space, however, not only can you create three-dimensional objects, but you can also modify the model space view to look at these objects from different perspectives. Consequently, model space is where your project design work should be performed.

The limitations of paper space for viewing three-dimensional objects is not a disadvantage. Remember, paper space is intended to be used to create the sheet plots of your model space project. It is not intended to be used for modeling. Therefore, use model space to design your project and use paper space to create your project's plots.

The next section focuses on the special properties of paper space viewports. Here, you learn to use paper space the way it is intended to be used: as an environment for creating sheet layouts for plotting purposes.

Creating Paper Space Viewports

Paper space viewports have unique properties for controlling the appearance of your project's model. By controlling layer visibility, hidden line removal, and model-to-paper space scale on a viewport-by-viewport basis, your finished plot can precisely display the objects necessary, even when you have several viewports on a single sheet. The capability to control how your model space project appears in paper space is a powerful tool.

The MVIEW Command

Creating viewports with paper space is a simple process. After the command is executed, MVIEW prompts for the following information:

ON/OFF/Hideplot/Fit/2/3/4/Restore/<First Point>:
Compare MVIEW's prompts with VPORTS' prompts:
Save/Restore/Delete/Join/Single/?/2/<3>/4:

Notice that MVIEW's command-line prompts differ from the VPORTS' commands. The differences are due to the varied properties that paper space and model space viewports possess. The most notable differences are paper space's capability to turn viewports on or off and its Hideplot feature.


TIP: You can copy MVIEW vport objects just like any AutoCAD entity. This is especially useful for duplicating properties such as zoom factor and display area. Simply copy or wblock an existing vport object.

Hidden Line Removal: Hide Lines versus Hideplot

AutoCAD provides two methods of removing hidden lines. The first involves removing them in model space by using the Hide Lines feature in the Print/Plot Configuration dialog box. The second involves removing them in paper space by using the Hideplot feature of the MVIEW command. Both commands work independently of each other.

The Hide Lines feature in the Print/Plot Configuration dialog box removes hidden lines only in the current space, as the following exercise demonstrates.

REMOVING HIDDEN LINES BY USING HIDE LINES AND HIDEPLOT

1. Open the 15DWG01.DWG drawing file on the accompanying CD.

The drawing opens in paper space.

2. Click on the Print button from the Standard toolbar.

The Print/Plot Configuration dialog box opens.

3. Under Additional Parameters, make sure the Hide Lines check box is selected.

4. Under Scale, Rotation, and Origin, make sure the Scale to Fit check box is selected.

5. Under Plot Preview, select Full, and then click on the Preview button.

AutoCAD displays a plot preview of the drawing.


NOTE: Notice that the arrowheads are not filled in, as shown in figure 15.5. These arrowheads reside in paper space. Also notice that the cylinder's hidden lines were not removed. The cylinder resides in model space. This illustrates that the Hide Lines feature in the Print/Plot Configuration dialog box works only in the current space.

Figure 15.5 Only the arrowhead's fill is removed when the Hide Lines feature is selected from the Print/Plot Configuration dialog box.

6. Press the Esc key.

The Print/Plot Configuration dialog box appears.

7. Click on the Cancel button.

8. From the View menu, choose Floating Viewports, Hideplot.

9. When prompted, enter ON and then select the viewport.

AutoCAD turns on the Hideplot feature for the selected viewport.

10. Click on the Print button from the Standard toolbar.

11. Under Additional Parameters, make sure the Hide Lines check box is not selected.

12. Under Scale, Rotation, and Origin, make sure the Scale to Fit check box is selected.

13. Under Plot Preview, select Full. Click on the Preview button.


NOTE: Notice this time that the arrowheads are filled in, as shown in figure 15.6. This is because Hide Lines in the Print/Plot Configuration dialog box was turned off. Also notice that the cylinder has its hidden lines removed. This is because you turned on hidden line removal for the viewport using MVIEW's Hideplot feature.

Figure 15.6 With MVIEW's Hideplot feature, the arrowhead's fill is not removed because they are in paper space. However, hidden lines are removed from the viewport.

14. Press the Esc key.

The Print/Plot Configuration dialog box appears.

15. Click on the Cancel button.

The Hide Lines feature of the Print/Plot Configuration dialog box only hides lines in the current space, whether it's paper space or model space. In contrast, the Hideplot feature of MVIEW sets hidden line removal independently for each paper space viewport. Consequently, if you have multiple viewports in paper space and need to hide lines in each one, the Hideplot feature must be turned on for each viewport by specifically selecting each viewport. After a drawing is plotted from paper space, the paper space viewports with Hideplot turned on will automatically remove hidden lines.


TIP: In the exercise, "Removing Hidden Lines by Using Hide Lines and Hideplot," the Hide Lines feature in the Print/Plot Configuration dialog box hides the arrowhead's fill. If you want the fill to appear, create a block of the arrowheads and insert it into paper space. When the arrowheads are defined as a block, AutoCAD erases them from model space. Then, instead of using the Hide Lines feature, use MVIEW's Hideplot feature to remove hidden lines in the viewport. This removes hidden lines in the viewport and does not affect the arrowhead fills inserted into paper space.

Aligning Objects in Paper Space Viewports

Paper space viewports can be edited in several ways. You can use grips to scale, move, or resize viewports. Viewports can be copied or erased. You can even create an array of viewports.

Although creating multiple viewports is easy, aligning objects in different viewports can be difficult unless you take advantage of the MVSETUP command.

The following exercise demonstrates how to use the MVSETUP command to align objects in two different viewports.

ALIGNING OBJECTS IN TWO DIFFERENT VIEWPORTS BY USING THE MVSETUP COMMAND

1. Open the 15DWG02.DWG drawing file, found on the accompanying CD.

When the drawing opens, it displays two viewports. Each viewport shows a different view of the same model space objects. It is important to note that the viewports both have the same scale.

2. Enter MVSETUP at the Command: line.

AutoCAD initializes the MVSETUP routine.

3. Enter A to start the Align feature.

4. Enter H to start the Horizontal feature.

AutoCAD prompts for the basepoint. The other viewport will be aligned to this point. If the lower-right viewport is not already highlighted, pick inside it to make it current.

5. With the lower-right viewport current, use endpoint snap to snap the small rectangle as shown in figure 15.7.

Figure 15.7 First, snap to the small rectangle in the lower-right viewport.

AutoCAD prompts for the other point. Pick inside the upper-left viewport to make it current.

6. With the upper-left viewport current, use endpoint snap to snap the small rectangle as shown in figure 15.8.

AutoCAD moves the view in the upper-left viewport down and aligns the two small rectangles.

Figure 15.8 Second, snap to the small rectangle in the upper-left viewport.

7. Enter V to start the Vertical feature.

Once again, AutoCAD prompts for the basepoint. Pick inside the lower-right viewport to make it current.

8. With the lower-right viewport current, use endpoint snap to snap the same small rectangle shown in figure 15.7.

AutoCAD prompts for the other point. Pick inside the upper-left viewport to make it current.

9. With the upper-left viewport current, use endpoint snap to snap the same small rectangle shown in figure 15.8.

AutoCAD moves the view in the upper-left viewport to the right and aligns the two small rectangles, as shown in figure 15.9.

Figure 15.9 The objects in the two viewports are aligned.

10. Press Enter twice to end the command.

Notice that the MVSETUP command was started in paper space, but ended in model space. Again, note that the objects in these two viewports aligned perfectly because both viewports have the same scale.

Setting Views in Paper Space Viewports

The purpose of paper space viewports is to create one or more views of your model space project. Typically in paper space, you create a viewport, zoom in to the area of your model that you want to display, and then plot it. Two things you should do when you position the display are:

The following exercise demonstrates how to properly scale model space objects in a paper space viewport and how to save the view once it is scaled.

SCALING MODEL SPACE OBJECTS IN A PAPER SPACE VIEWPORT

1. Open the 15DWG03b.DWG drawing file found on the accompanying CD.

The drawing opens with TILEMODE set to 0 (off) and in model space. The sheet border is in paper space, and the xrefed objects are in model space. The black box surrounding the xref object is the polyline that was used to XCLIP the xref.


TIP: This drawing represents a typical layout for a street improvement plan. In practice, it is a good idea to create a sheet border in paper space and attach the model as an xref. Additionally, each drawing file should contain only one sheet. Avoid having multiple sheets in a single drawing file. By having only one sheet per drawing, you decrease the number of viewports in paper space. The fewer viewports, the faster your drawing regens.


TIP: When working with large xref files, use the XCLIP command to display only the necessary model space objects. This reduces regen time and increases productivity.

2. Enter MVSETUP at the Command: line.

AutoCAD initializes the MVSETUP routine.

3. Enter S to start the Scale viewports feature.

AutoCAD prompts you to select the viewports to scale. Notice that AutoCAD switched to paper space.

4. Select the viewport and then press Enter.

AutoCAD prompts you to enter the ratio of paper space units to model space units. In this case, you want to scale the model space objects to 1:50 (1" = 50').

5. When prompted for the number of paper space units, enter 1.

6. When prompted for the number of model space units, enter 50.

AutoCAD scales the model space drawing to the correct ratio as shown in figure 15.10.

Figure 15.10 The properly scaled model space objects.

7. Press Enter to end the MVSETUP command.

With the view properly positioned and scaled, save the view.

8. Enter V at the Command: prompt.

The View Control dialog box is displayed.

9. Click on the New button.

The Define New View dialog box is displayed.

10. Enter PLAN in the New Name text edit box. Be sure the Current Display option is selected and then click on the Save View button. Click on OK.

With the view saved, it is now possible to quickly restore the original view at the proper scale. If the model space objects are panned or zoomed, the view can quickly be restored from the View Control dialog box.


WARNING: You can only use the View Control dialog box to restore a saved view if the viewport is not resized.

Controlling Paper Space Viewport Visibility

Paper space viewports provide the capability to freeze and thaw layers individually. This can be done within the Layers dialog box, from the Layer Control on the Object Properties toolbar, or by using the VPLAYER command. The advantage of using the Layers dialog box or the Layer Control is that you can simply choose the Freeze/Thaw in current viewport icon to toggle layer visibility on or off. The disadvantage is that the settings only affect the current viewport. In order to set the same layer freeze/thaw properties in multiple viewports, you must make each viewport current and then choose the desired setting. The advantage of using the VPLAYER command is that you can apply the desired freeze/thaw settings to multiple viewports at the same time. Unfortunately, you must type in the layer names.


WARNING: Although you can control a layer's freeze/thaw property in the current viewport, the global freeze/thaw value can override a viewport's setting. If a certain layer is thawed in a viewport but frozen globally, for example, the layer will not appear in any viewports.

The following exercise demonstrates the usefulness of the Layer Control and the VPLAYER command.

CONTROLLING LAYER VISIBILITY IN PAPER SPACE BY USING THE LAYER CONTROL AND THE VPLAYER COMMAND

1. Open the 15DWG04.DWG drawing file on the accompanying CD.

The drawing opens in paper space (TILEMODE = 0) and displays the two viewports. At this point, it is obvious that there are layers that are not visible in the viewport on the right.

Next, you determine which layers are frozen in the viewport on the right.


2. Choose the down arrow on the Layer Control.

The control opens and displays the list of layers as shown in figure 15.11. Notice that the icons indicate that all layers are on and thawed.

Figure 15.11 The Layer Control indicates that all layers are on and thawed.

3. Choose the down arrow on the Layer Control to close the list of layers.

4. Double-click the PAPER tile in the status bar at the bottom of the screen.

AutoCAD switches from paper space to model space, and the right viewport becomes active.

5. Choose the down arrow on the Layer Control.

The control opens and displays the list of layers as shown in figure 15.12. Notice that the icons indicate that three layers are frozen in the current viewport.

Figure 15.12 The Layer Control indicates that three layers are frozen in the current viewport.

6. Choose the down arrow on the Layer Control to close the list of layers.

7. Double-click the MODEL tile in the status bar at the bottom of the screen.

AutoCAD switches from model space to paper space.

The next part of this exercise uses the VPLAYER command to list the frozen layers in the two viewports.


8. Enter VPLAYER at the Command: prompt.

9. Enter ? at the Command: prompt.

AutoCAD prompts you to select a viewport.

10. Select the right viewport.

The following information is displayed:

Layers currently frozen in viewport 3:
CONTOURS-INDEX
CONTOURS-NORMAL
MODEL_SPACE_BORDERS

AutoCAD lists the layers frozen in the selected viewport. To list frozen layers in other viewports, repeat steps 9 and 10.

11. Enter ? at the Command: prompt.

12. Choose the left viewport.

The following information is displayed:

Layers currently frozen in viewport 2:
MODEL_SPACE_BORDERS


NOTE: Notice that the VPLAYER command listed the first viewport selected as viewport 3 and the second as viewport 2. Although only two paper space viewports appear in this drawing, the original paper space view is considered viewport 1.


The next steps use the global freeze/thaw layer settings to set both viewports' current freeze/thaw layer settings.

13. Press Enter to end the VPLAYER command.

14. Click on the Layers button.

The Layer & Linetype Properties dialog box opens.

15. Set the Freeze in New Viewports value to frozen for all layers except layer 0, as shown in figure 15.13.


TIP: To view a column's entire heading, click and drag the line separating column titles until the heading is visible.

Figure 15.13 The Freeze in New Viewports value is set to frozen for all layers except layer 0.

16. Click on OK to accept the changes and close the dialog box.

17. Enter VPLAYER at the Command: prompt.

18. Enter R for reset.

19. Enter * to reset all layers' values to the Freeze in New Viewports values.

20. Enter S for Select.

21. Select the two viewports.

22. Press Enter to end the VPLAYER command.

The two viewports' current viewport freeze/thaw values are set to the Freeze in New Viewports values in the Layer & Linetype Properties dialog box. Consequently, only the road alignment is visible, as shown in figure 15.14.

Figure 15.14 The current viewport layer freeze/thaw values are automatically set by using the VPLAYER Reset feature.


TIP: When you have multiple viewports to which you need the same current viewport freeze/thaw values, use the technique of setting the Freeze in New Viewports values to the desired values in the Layer & Linetype Properties dialog box. Then use the VPLAYER's Reset feature to select the viewports and automatically update their current viewport freeze/thaw values.


NOTE: You might have experienced a problem with retaining changes you made to layer values for xref objects after you closed the drawing and reopened it. If you make changes to the layer values of xrefs, and you want those values to be saved with the drawing, set the VISRETAIN system variable to 1. This instructs AutoCAD to save any changes you make along with the drawing.

New Paper Space Features

With Release 14 comes two welcome improvements to working in paper space. First, changing the display in paper space by zooming or panning no longer automatically invokes a regen, which is an important time-saving feature. Second, real-time and transparent zooming and panning are now supported in paper space.

The next section explores AutoCAD's dimensioning tools and explains how these tools work when dimensioning in model space and paper space.

Dimensioning in Model Space and Paper Space

AutoCAD provides a powerful set of dimensioning tools. Using these tools may seem overwhelming in the beginning because of the number of dimension system variables used to control a dimension's properties (approximately 60 different dimension variables exist). Fortunately, most of these system variables are easily controlled through the Dimension Styles dialog box. Although this section is not intended to provide a detailed explanation of how to use AutoCAD's dimensions, it discusses two particular system variables and how they work in paper space and model space.

As a CAD technician, you have the choice of dimensioning objects in model space or paper space. Depending on your company's drawing standards, or the needs of your client, you will probably be required to draw dimensions in one space or the other. Model space objects are typically drawn at real-world scale, however, while paper space viewports display model space objects at a reduced scale. Consequently, when dimensioning in model space, a certain scale factor must be used to correctly determine dimension values. In paper space, however, the reduced scale must be taken into consideration when determining a dimension's value. For AutoCAD to correctly calculate a dimension's value in either space, it relies on two particular system variables.

The variables are:

For information on dimensioning beyond the scope of this chapter, see Chapter 18, "Productive Dimensioning," and Chapter 19, "Advanced Dimensioning."


TIP: You can place your MVIEW vport objects on the DEFPOINTS layer to control plotting. The DEFPOINTS layer is created whenever you make your first dimension. One of its unique properties is that objects on it do not plot. By placing the vport on this layer, you don't have to worry about freezing the layer for the vports. Having them available at all times can be quite a time-saver.

Using the DIMSCALE System Variable

The DIMSCALE system variable sets the overall scale for the size of dimension objects. When plotting from model space, it should be set to the intended plot scale. If your final plotted sheet is going to be plotted at 1"=40' (1:40) scale, for example, the DIMSCALE value should be set to 40. Consequently, when dimensions are drawn, AutoCAD will automatically scale the size of the text, arrowheads, and other dimension geometry to the correct size.

But DIMSCALE is a fixed-scale factor. If you have a situation where your plot has two viewports, one at 1"=40' and the other at 1"=20', the viewport with the 1:20 scale ratio will have its dimension geometry two times too big, as shown in figure 15.15.

Figure 15.15 A problem arises if you draw dimensions in viewports with different scale factors.

Notice in figure 15.15 that the dimension text in the upper viewport is smaller than the dimension text in the lower viewport. The upper viewport's text size is correct for the intended plot scale of the sheet. The problem is how to account for the different scale factor in the lower viewport.

AutoCAD solves this dilemma with a special value for DIMSCALE. When you draw dimensions in paper space viewports (TILEMODE = 0), set the DIMSCALE variable to 0. This instructs AutoCAD to set the dimension's size relative to the viewports scale factor. This is true for every viewport in paper pace, even if they have different scale factors.

The following exercise demonstrates what happens when DIMSCALE is set to 0 and dimensions are drawn in model space with TILEMODE set to 0.

SETTING MODEL SPACE AND PAPER SPACE DIMENSION SCALES BY SETTING DIMSCALE AND DIMLFAC SYSTEM VARIABLES

1. Open the 15DWG05.DWG drawing file, which can be found on the accompanying CD.

The drawing shown in figure 15.15 opens.


NOTE: I used the XCLIP command to clip a boundary around the area I wanted to see in the viewport. In this case, instead of inserting the topo as an xref, I inserted it as a block. As you can see, the XCLIP command clips blocks as well as xrefs.

2. Enter DIMSCALE at the Command: prompt.

AutoCAD issues the following prompt:

New value for DIMSCALE <40>:

This shows that the current value for DIMSCALE is 40. This was the dimension scale factor applied to the dimensions when they were drawn.

3. Press Enter to accept the default value of 40.

4. From the Dimension menu, choose Style.

The Dimension Styles dialog box opens.

5. Click on the Geometry button.

The Geometry dialog box opens. Notice under Scale that the Overall Scale value is 40. This is the value of DIMSCALE.

6. Select the Scale to Paper Space check box.

A check mark appears in the box and the Overall Scale feature is set to 0 and grayed out, as shown in figure 15.16.

Figure 15.16 Scale to paper space is turned on in the Geometry dialog box.

7. Click on OK and then click on OK again to close both dialog boxes.

The DIMSCALE variable is now set to 0.


Next, you will draw the same dimensions again to view how AutoCAD handles the two viewports' different scale factors.

8. Double-click the PAPER tile in the status bar at the bottom of the screen.

9. Choose the lower viewport if it is not the active viewport.

10. From the Layer Control, select the 10_scale layer to make it current.

11. From the Dimension menu, choose Aligned.

12. Snap to the intersection of the centerline and the number 4 tick mark.

13. Snap to the intersection of the centerline and the number 5 tick mark.

14. Drag the dimension value to just below the existing dimension.

15. Choose the upper viewport to make it active.

16. From the Layer control, choose the 40_scale layer to make it current.

17. From the Dimension menu, choose Aligned.

18. Snap to the intersection of the centerline and the number 4 tick mark.

19. Snap to the intersection of the centerline and the number 5 tick mark.

20. Drag the dimension value above the centerline to about the same position as the existing dimension.

Your drawing should look similar to figure 15.17. Notice that the dimension text you just created is the same size in both viewports. With DIMSCALE set to 0, AutoCAD correctly sized the dimension object's geometry automatically.

Figure 15.17 With DIMSCALE set to 0, the dimension's geometry is scaled correctly.

Setting DIMSCALE to 0 works great when you are drawing objects in model space viewports, but how can you instruct AutoCAD to accurately determine the distance between two points when you are in paper space?

AutoCAD has another dimension variable called DIMLFAC that multiplies distances measured in paper space by a viewport's scale factor.

To demonstrate this feature, continue with the previous exercise.

USING DIMLFAC TO SCALE IN PAPER SPACE

1. Double-click the MODEL tile in the status bar at the bottom of the screen.

2. Enter DIM at the Command: prompt to automatically set the DIMLFAC value.

3. Enter DIMLFAC at the Command: prompt.

AutoCAD indicates that the current value of DIMLFAC is -40, and it prompts for a new value.

4. Enter V for viewport.

5. Select the lower viewport.

AutoCAD sets the value of DIMLFAC to -20. This value is derived from the viewports scale factor, which is 1/20.

6. Enter EXIT to quit the DIM command.

7. Zoom in to the lower viewport.

8. From Layer Control, choose the 0 layer to make it current.

9. From the Dimension menu, choose Aligned.

10. Snap to the intersection of the centerline and the number 4 tick mark.

11. Snap to the intersection of the centerline and the number 5 tick mark.

12. Drag the dimension value below the centerline. Your drawing should look similar to figure 15.18.

13. Close the drawing and save your changes if you want.

Notice that the dimension text you just created is the same size as the previous dimension text you created. More important, notice that AutoCAD calculated the correct distance, even though the measurement was made in paper space. With DIMSCALE set to 0 and DIMLFAC set to -20, AutoCAD correctly sized the dimension object's geometry and correctly determined its length.

Figure 15.18 With DIMLFAC set appropriately, the dimension's distance value is calculated correctly.

Dimensioning in model space and paper space has advantages and disadvantages. In model space, associative dimensioning automatically updates a dimension as objects in model space are edited. If the dimension is drawn in paper space and the model space objects are edited or change shape, or if the model is moved or rescaled in its paper space viewport, however, the dimensions drawn in paper space will not update. They will have to be edited separately or redrawn.

The advantage of drawing dimensions in paper space is that all dimensions can reside on the same layer. As demonstrated in the previous exercise though, multiple layers are needed for each viewport in which dimensions are drawn. This is necessary so that layers can be frozen or thawed as required to display only the dimensions appropriate for a particular viewport.

Summary

This chapter covered paper space basics and why you should use paper space. You learned about the TILEMODE system variable and the difference between tiled and untiled, or floating, viewports. Comparisons of model space versus paper space were presented, as well as the differences between the Hide Lines and Hideplot. You learned about Release 14's new paper space features, and how to use the MVSETUP command to align model space objects in different viewports. You also learned the value of saving scaled views with the DDVIEW command and how to quickly change multiple viewport's current layer freeze/thaw values. Finally, you learned how to set dimension variables properly to be drawn in paper space viewports or in paper space.

This chapter has shown you how to use AutoCAD 14's Paper Space feature in productive ways. By using the techniques discussed, you can easily control the appearance of your final drawings and ease the time-consuming process of dimensioning, thereby increasing your productivity.


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