Autocad Lost Drawing on Model

Lost in Paper Space (The Sequel)

30 Sep, 1996

By: Lynn Allen

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Last month, we covered some basics of Paper Space. I hope you've been dutifully applying this information in your drawing procedures and now feel comfortable with these concepts. This month, we'll review the basics and proceed into some of the more complicated aspects of Paper Space. Our goal is to be able to annotate and plot our drawings at a scale of 1:1-WYSIWYG: What you see is what you get. We are trying to make our daily lives with AutoCAD easier. We also want to be able to have one drawing with multiple scale factors and be able to plot multiple viewpoints of our three-dimensional drawings.

Let's step through the process so far:

1. You are in Model Space-because tilemode is set to 1. Create your model at a 1:1 scale. Do not place any dimensions or text on your drawing.
2. Now, you're ready to enter the Paper World by setting tilemode to 0. You can also enter the Paper World by double clicking on the Tile button on the Status bar (Release 13 for Windows only). You will know you're in the Paper World because the UCSICON in the lower-left-hand corner of your drawing screen now resembles a triangle. Set your limits to equal the size of the paper you'll be plotting on. Insert a title block if desired.
3. Create a viewport layer and make it current. Now, we'll go get the model and place it on the paper. This process is done with the MVIEW command. Pick the two opposite corners of a window you'd like your model to fit into on your paper. Put a couple of viewports of your model in your drawing, so we have something to work with.

Should you choose to work within the viewports on your model (while in the Paper World), you can key in MS (for Model Space). You can also click on the Paper Space button on the status line (Windows R12 or R13 only). This action will not change the value of tilemode, but it will make one of the viewports active (or current). You can move from viewport to viewport by picking within the desired viewport. You can also use <Ctrl+V> to change the active viewport. Notice that, as you Pan and Zoom, you're just modifying the display within the active viewport. If you key in PS to return to Paper Space and Zoom, you'll see you're zooming relative to the entire sheet of paper.

Golden rule: Those things you create in Paper space can only be edited within Paper Space. Those things you create in Model Space can only be edited within Model Space.

Now, we're ready to dive deeper into the world of Paper Space. You should have at least two viewports of your model on your screen. Make one of the viewports active by keying in MS (or clicking on the status line).

Scale Factors
What scale factor are our models using? We created them at 1:1, full scale, but who knows what they are set to now? We must be able to control the scale factors of these models with the viewports, which is done by using the XP option within the trusty ZOOM command-not exactly a logical assumption. XP stands for "Times Paper Space." The next part gets a little confusing.

What would you like your scale factor to be within this viewport? One-quarter inch equals one foot? Or did you create something really small that you'd like to make larger with a scale factor of 2:1? Let's start with the simple architectural scale factor of 1/4"=1'.

If you were drafting on a piece of paper, the scale factor of 1/4"=1' would mean that you were scaling everything down to fit on your paper. In fact, you'd be dividing all the real world measurements by 48. Where did I get 48? Simple: 1/4=12 is the ratio. So take 4, multiply it by 12, and you get 48; you end up with 1/48. 1/2"=1' gives you 1/24, 1"=1' gives you 1/12, and so on.

To scale objects up: 2:1 is equal to 1 divided by 2 yielding .5, 4:1 is equal to 1 divided by 4 yielding .25, and so on.

Table 1 Scale Factors
3 inches = 1 foot	ZOOM 1/4 XP
3/4 inch = 1 foot	ZOOM 1/16 XP
1/2 inch = 1 foot	ZOOM 1/24 XP
3/8 inch = 1 foot	ZOOM 1/32 XP
1/4 inch = 1 foot	ZOOM 1/48 XP
1/8 inch = 1 foot	ZOOM 1/96 XP
2 inches = 1 foot	ZOOM .5XP
4 inches = 1 foot	ZOOM .25XP
1 inch = 1 foot	ZOOM 1/100 XP

If you want the scale factor within one of your viewports to be 1/4"=1', enter the ZOOM command within the desired viewport and then enter 1/48XP. This command will divide your full-scale model by 48 within the viewport. You can easily make another viewport active and set the scale factor to something different by entering the ZOOM command and setting a different XP value. After setting the appropriate ZOOM scale factor, use the PAN command in the viewport to position the model properly within the viewport. See how easy it is to have multiple scale factors per drawing when you use Paper Space? A chart for some basic scale factors is shown in Table 1.

Remember, we're just taking the full-scale model and scaling it down to fit on the paper.

Dimensioning
So, you've set up your viewports to the proper scale factor. Now, how do we go about dimensioning our model? Should we do it in Paper Space or Model Space? We'll be in the Paper World (tilemode is off), but we'll dimension within the floating viewports (Model Space).

While in Paper Space, Zoom up on the viewport you will be dimensioning. Switch over to Model Space, and make it the active viewport. Create and set a layer specifically for the dimensions you will be placing within this viewport. To ensure that we get properly scaled dimensions, we'll select the Scale to Paper Space option within the DDIM dialog box (Release 13). If you're in Release 12, select Use Paper Space Scaling within any of the dialog boxes accessed by DDIM. Behind the scenes, we're actually setting the dimension variable dimscale to 0. Set all the other dimension variables to the actual settings you want the dimensions to have (WYSIWYG). If you want the text to be 3/8-inch high, you should set the dimension text to that height.

Here's the tricky part: when you dimension, AutoCAD will look at the scale factor set within the viewport and use that value to calculate the outcome of the size of the final dimension. It does this calculation automatically, to ensure that you get the text, dimension lines, extension lines, and so on exactly the size you want without any extra hassle. AutoCAD does all the calculations for you. You only need to set this up once and it works for all viewports.

Should you choose to dimension another viewport, you simply switch to another viewport, create and set another layer for these new dimensions, and dimension away. AutoCAD will reevaluate the scale factor for this new viewport.

You may have noticed that the dimensions from the first viewport are showing up in the second viewport. This situation may not be desirable, which brings us to the next topic: the ability to control layer visibility from viewport to viewport.

Viewport Layer Control
One of the most impressive benefits of using Paper Space is the ability to control layer visibility per viewport. For example, you might have the DIM1 layer visible in one viewport but not in another. This feature is very important to the success of Paper Space. You can't do that with the standard tiled viewports of the Model World.

Paper Space has its very own LAYER command called VPLAYER (ViewPort Layer). VPLAYER allows you to freeze or thaw individual layers per viewport. We'll start off with this command-prompt driven command and then migrate to DDLMODES, the Layer dialog box.

You must have tilemode set to 0 to enter the VPLAYER command. If a layer is already universally frozen (LAYER command), you cannot use VPLAYER to affect its visibility. The standard LAYER command always wins. VPLAYER can be found in the Data pull-down menu under Viewport Layer Controls (Release 13). If you are in Model Space when you execute this command, VPLAYER will automatically switch to Paper Space when needed. When the command is completed, you will be returned to Model Space. The VPLAYER command permits the use of wildcards as well (* and ?). It's often faster to enter the VPLAYER command and use wildcards than it is to manually select a group of layers in the layer dialog box. You'll see many Paper Spacers using this command on a regular basis, even though it's command-prompt driven because of its extra capabilities.

Command: vplayer

?/Freeze/Thaw/Reset/Newfrz/Vpvisdflt:

1. The ? option provides a list of the frozen layers in the selected viewport.
2. The Freeze option is used to specify the layers you want to freeze. The following three suboptions will appear when you use Freeze: All freezes the specified layer(s) in all viewports, Select freezes the specified layer(s) in the viewports you select, and Current freezes the specified layer(s) in the current viewport only.
3. The Thaw option thaws the specified layers in the selected viewports. When you use Thaw, the same three suboptions listed for Freeze will display.
4. The Reset option resets the layers back to the default frozen or thawed state (see VPVISDFLT). You can reset the layers in the Current viewport, All the viewports, or Selected viewports.
5. The Newfrz (New Freeze) option is used to create new layers that are frozen in all viewports. Why would you want to do that? When you have multiple floating viewports in your drawing, you often need to create a new layer that is visible in only one viewport. Use the Newfrz option to create this new layer, which will be frozen in all the viewports. Then, go to the desired viewport and thaw that new layer. This process is much easier than creating the layer and then freezing it in all of the other viewports. I know it seems like a roundabout way of achieving something, but it works!
6. The VPVISDFLT (Viewport Visibility Default) option is the last. If this option doesn't intimidate you, nothing in AutoCAD will! Before explaining this option, let me set up an appropriate scenario (because I'm sure your head is swimming by now).

Paper Space is an ideal method of creating detail sheets. Let's say you have many different drawings that contain your details. You just want to get those details and bring them all together into one final sheet. Start a new drawing, and go immediately to Paper Space. Set up your paper (tilemode is off) and create your first MVIEW. The first detail will go here. Enter the viewport (MS), execute the XREF command, and attach the first detail drawing.

If you create another viewport for your next detail, you'll see that your first detail inconveniently displays in your second viewport as well. What to do? You could enter the VPLAYER command and use the Freeze option to freeze all the layers in the new viewport. But you would end up freezing layers in all subsequent viewports as well. The VPVISDFLT option comes into play at this point. Before creating your second viewport, you can tell AutoCAD that you want to freeze all those layers from the first detail in all new viewports. Because external references assign the drawing name as a prefix to the layer names, it is easy to use wildcards to control this layer visibility.

You can use VPVISDFLT to Freeze or Thaw layers in new viewports. If you accidentally put the cart before the horse by creating the viewport first and then realizing you need to change the VPVISDFLT, it's not a problem. You can use the Reset option to update any existing viewports.

Have I lost you yet? As I mentioned in my previous article, Paper Space is difficult to explain. But when the lightbulb goes on, you'll realize how simple and logical Paper Space actually is. You'll wonder how you survived without it, and you'll insist on showing your newfound expertise to your coworkers.

Let's look at DDLMODES. Though somewhat more limited than VPLAYER, you might find this visual control easier than VPLAYER. Before entering DDLMODES, be sure to enter Model Space and set your current viewport to the one you want to modify. DDLMODES only affects the current viewport, as shown in Figure 1.

CurVP
Located on the right-hand side of the Layer dialog box, CurVP controls the visibility of layers within the current viewport. Thw will thaw the highlighted layers, Frz will freeze them. When a layer is frozen in the current viewport, a C appears next to the selected layer in the Layer dialog box. After hitting the final OK, AutoCAD will regenerate all the viewports and update the drawing to reflect the changes.

NewVP
Also located on the right-hand side of the Layer dialog box, NewVP controls the visibility of layers in all new viewports. When selected, an N will appear next to the selected layer. This option is similar to the Vpvisdflt option in VPLAYER.

Miscellaneous Notes
If you have multiple floating viewports within Paper Space, regenerations can get painful because AutoCAD insists on regenerating every single viewport. If you don't need to use a viewport for awhile, by all means, turn the viewport off (MVIEW command). Though AutoCAD can display an unlimited number of viewports, your operating system determines the number of viewports that can be active at any given time. The MAXACTVP system variable internally controls the maximum number of active viewports AutoCAD will enable at any given time. The default value is 16, but a lower setting could improve your performance because inactive viewports are not regenerated.

If you plan to use xrefs in Paper Space, be sure to turn visretain to 1. This setting will ensure that your Layer settings (which you've so carefully set up) are saved with your drawing.

When you plot multiple viewports, by default, AutoCAD will not remove hidden lines. To remove hidden lines within viewports, you will need to use the MVIEW command (Hideplot option) to select the desired viewports (see last month's column).

Crucial for the Release 12 users is the psltscale variable. When set to a value of 1, AutoCAD uses the scale factor within the viewport to control the linetype scaling. This setting permits different magnifications while displaying identical linetypes.

So, now that you've set up your viewports, you might want the box to disappear around the edges of the viewport. Make sure you are in Paper Space, then freeze the layer on which you've placed the viewports. You'll find yourself with a finished drawing with multiple scale factors and views. When you create your final plot, the scale factor is 1:1. It couldn't be easier.

Now, let me step through the entire process one last time.

The 10 Steps of Paper Space

1. Tilemode is set to 1. You are in the Model World. Create your model at a 1:1 scale factor.
2. Go to the Paper world. Tilemode is set to 0. Set up your limits, units, grid, snap, and so on for the actual paper to which you plan on plotting. Insert a border if desired.
3. Create and set a layer for your viewports. Be sure to use this layer for viewports only because you'll be freezing this layer when you make your final plot.
4. Use the MVIEW command to bring in your model.
5. Enter MS, and scale your model using the ZOOM XP option. Pan your drawing around if necessary to position it properly within the viewport.
6. Dimension the model. Be sure to set the dimensioning scale factor to Scale to Paper Space (or set dimscale to 0). If you have multiple viewports, use a different dimensioning layer for each viewport.
7. While in Paper Space, annotate your drawing. Set the text height to the actual size you want the final text to plot.
8. Use the MVIEW command to select any viewports in which you want AutoCAD to perform a hidden line removal (3D users only).
9. Freeze the viewport layer.
10. Plot at a scale factor of 1:1.

Though this overview of Paper Space is fairly comprehensive, there are still many minor subtleties you will discover over time. I hope the lightbulb went on for at least some of you. Practice and patience are essential to Paper Space survival. Good luck!

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