Autocad Drawing "Space"

Model Space And Paper Space


There are two modes of drawing in AutoCAD, also called "SPACE." The normal mode and the default is called "Model Space." This is the space you will use almost all of the time. It is the normal 3 dimensional world in which all of your buildings are drawn, both in 2-dimensions (plans, elevations, sections) and in 3-dimensions (perspectives or axonometrics). In this space, objects are always drawn in real world units, full size.

The other mode of drawing or space is called "Paper Space." This space permits only a 2-dimensional world, and can be visualized as a flat sheet of paper. Paper Space is a 2-dimensional drawing mode in which you can group various "views" of a 3-dimensional drawing in "holes" of the paper called "viewports" for plotting. It is useful for plotting several views of an object at different scales, or for putting orthogonal drawing titles on a perspective or axonometric drawing. There is no other method in AutoCAD of combining drawings of different scales on the same sheet of paper, without changing the actual size of the objects or plotting each detail separately. When in Paper Space, the word "PAPER" appears in STATUS BAR at the bottom of the AutoCAD desktop, and a 30-60 degree triangle with the letter "W" within it appears at the lower left corner of the drawing.

A "Viewport" is a rectangular area or hole in the paper through which you view your "Model." There is no limit to the number of viewports you may have in any drawing. Viewports can be copied, moved, erased, and stretched to give you just the right appearance. Only one viewport can be active in Model Space at a time. To make a viewport active, switch to model space and click within the viewport you want to make active with the pick button of the mouse. Watch Out! You could have several viewports laying on top of one another, without you even being aware of it. If you have a viewport within another viewport, you can switch from viewport to viewport either by clicking in each viewport or by holding down the <Ctrl> key and typing the letter R. As you continue to type <Ctrl> R, you will toggle from viewport to viewport, making them each active one at a time, in the order they were created.

Each viewport may have a different view of the model within it. For instance, when you have drawn a 3-dimensional drawing of a building, you can have its plan shown in one viewport, its front elevation in another one, its side elevation in another one and a perspective view of it in another one. When the 3d model is later revised, all viewport appearances are updated automatically to reflect the changed model. Thus, you can draw the building only once, but view it in many forms and from many directions.

By definition, viewports are entities in Paper Space, so that is the space in which they are created or modified. When you use the MV command to create a viewport, make sure that the current layer is the one that you want your viewport entities to be in. Normally you do not want the actual rectangle which surrounds the viewport to plot or print. To prevent this, you could place your viewports on a layer that could be frozen just before plotting, such as the layer "A-ANNO-VPRT." Alternatively, some drafters create viewports on the "DEFPOINTS" layer. The "DEFPOINTS" layer is a special layer which AutoCAD automatically creates for its own use to place dimension definition points (which are points at the ends of extension lines from which the dimension is measured). The unique thing about that layer is that it can be visible on the screen (unless it is frozen), but it never will show up on a plot or print.

Each viewport is able to display the model at different zoom scale factors (i.e. larger or smaller), is able to show the model from different points of view (horizontal, vertical, or obliquely, and is able to freeze or thaw layers individually within each viewport separately. In other words, you may freeze the A-NOTE layer in one viewport, but have it thawed in another. You cannot change the color or linetype characteristics of a layer from one viewport to another, however (more's the pity!).
 To go to paper space, click on a tab at the bottom of the drawing which is not the "Model" tab. These are layouts and when you open a new drawing there is at least one layout tab. The layouts can contain viewports. You can think of a layout as a sheet which will be plotted that has holes cut into it (called "viewports") through which you can see your model drawing in various scales and directions.

What Should Be Drawn in Paper Space?

The following is a list of entities which are typically drawn in Paper Space. All other entities should be drawn in Model Space:

  1. Viewports (on either A-ANNO-VPRT layer, or DEFPOINTS layer)
  2. Sheet border and title (on A-ANNO-BORD layer)
  3. Individual drawing titles, scales and North Arrows (on A-ANNO-NOTE layer)
  4. Revision "clouds" and revision numbers in triangular symbol (on A-ANNO-REVS layer)



    Autocad does not use a scale -- you always draw everything FULL SIZE. You have an unlimited size drawing board in AutoCAD which can grow with the physical size of the building. You normally would determine the scale at the time you plot the drawing out. However, in order for certain items like text and dimensioning to have a good size relationship to the lines of the drawing, you will need to have a final scale in the back of your mind before you start a drawing.

    Scale in Paper Space

    Normally, you will draw a so-called "model" of your building in standard AutoCAD "Model Space," which is the world of three dimensions. In order to plot various views of this three dimensional "model" on the same sheet of paper and to some scale, you will normally create several "viewports" in AutoCAD "Paper Space" which is a two-dimensional composing area, as described in the previous pages. In Paper Space you can mix various scales, plans with elevations and perspectives, without changing the actual model. Paper Space is simply a way of consolidating several views on the same plot. The model itself is drawn always at full size, but when inserted into the plotted sheet in a viewport, each viewport is "scaled" to its proper plot scale factor.

    The great advantage of paper space drawings is that they can be plotted at 1 to 1 (that is, no scale reduction). However, if you want the drawings you do of the "model" to be plotted to a scale, you have to assign a scale to each viewport. Scale is one of the properties of a viewport. Click on the viewport rectangle and set its scale through the properties palette. Or, you may double click inside the viewport and set the scale by typing Z <RET> 1/48xp <RET> (that is the example for 1/4" = 1'-0" scale)

    The table below lists proper viewport scale factors for plotting models in paper space to a scale.
    Be very careful to include the "xp" at the end of the zoom factor.

    Zoom Factors For Paper Space Scaling

    Architect's Scales Viewport Zoom Factor (in Model Space)
    1/16"=1'-0" 1/192xp
    3/32"=1'-0" 1/128xp
    1/8"=1'-0" 1/96xp
    3/16"=1'-0" 1/64xp
    1/4"=1'-0" 1/48xp
    3/8"=1'-0" 1/32xp
    1/2"=1'-0" 1/24xp
    3/4"=1'-0" 1/16xp
    1"=1'-0" 1/12xp
    1 1/2"=1'-0" 1/8xp
    3"=1'-0" 1/4xp
    Half Size 1/2XP
    Full Size 1xp
    Engineer's Scales Viewport Zoom Factor (in Model Space)
    1"=1000'-0" 1/12000xp
    1"=500'-0" 1/6000xp
    1"=100'-0" 1/1200xp
    1"=50'-0" 1/600xp
    1"=30'-0" 1/360xp
    1"=20'-0" 1/240xp
    1"=10'-0" 1/120xp
    Metric Scales Viewport Zoom Factor (in Model Space)
    1:10 1/10xp
    1:20 1/20xp
    1:50 1/50xp
    1:100 1/100xp
    1:500 1/500xp

    Size of text and dimensions in Model Space

    Most architectural plans and elevations for houses and small buildings are traditionally drawn at 1/4" = 1'-0" scale. Other buildings use 1/8" = 1'-0" scale. Details are drawn at 1 1/2" = 1'-0" or 3" = 1'-0" scale. Each of these drawing scales will need to have a corresponding text size and dimensioning scale (the "DIMSCALE") set. In other words, if you want the final text size on a plotted drawing to appear to be 1/4" in height, and you plot the drawing at 1/4" = 1'-0" scale, you will have to draw the actual text at a 12" height in AutoCAD. This is a difficult idea to get used to, but is a natural result of drawing everything at full size.

    Size Multipliers for Text and Dimensions

    Scale of Plotted Drawing Text and Dimension Size Multiplier
    1/16"=1'-0" 192
    3/32"=1'-0" 128
    1/8"=1'-0" 96
    3/16"=1'-0" 64
    1/4"=1'-0" 48
    3/8"=1'-0" 32
    1/2"=1'-0" 24
    3/4"=1'-0" 16
    1"=1'-0" 12
    1 1/2"=1'-0" 8
    3"=1'-0" 4
    Half Size 2
    Full Size 1
    Engineer's Scales Text and Dimension Size Multiplier
    1"=1000'-0" 12000
    1"=500'-0" 6000
    1"=100'-0" 1200
    1"=50'-0" 600
    1"=30'-0" 360
    1"=20'-0" 240
    1"=10'-0" 120
    Metric Scales Text and Dimension Size Multiplier
    1:10 10
    1:20 20
    1:50 50
    1:100 100



    (Note: The following will not be necessary if drawings are always plotted in Paper Space)

    If you do not intend to make use of Paper Space to plot several views of a model, but instead have several independent two-dimensional drawings which need to be combined on the same sheet of drawings, you may choose to change the relative sizes of some of the details so that they appear to be drawn at a larger or smaller scale. Although this process is not recommended for many reasons, you may find occasion to use this technique.

    If you want to include a detail or other drawing on a model space plotted sheet along with other drawings which will be plotted at another scale, you should work on the detail separately first in its full size mode and then insert the finished detail onto the sheet you want it to appear, scaling while inserting. The scale conversion factors are as follows:

    Drawing plot scale Detail scale desired Conversion Factor (insert detail at this scale)
    1"= 20'-0" 1/8" = 1'-0" 2.5
    1/4" = 1'-0" 5
    1/2" = 1'-0" 10
    3/4" = 1'-0" 15
    1"= 1'-0" 20
    1 1/2" = 1'-0" 30
    3" = 1'-0" 60
    Half size 120
    Full size 240
    1/8" = 1'-0" 1/4" = 1'-0" 2
    1/2" = 1'-0" 4
    3/4" = 1'-0" 6
    1"= 1'-0" 8
    1 1/2" = 1'-0" 12
    3" = 1'-0" 24
    Half size 48
    Full size 96
    1/4" = 1'-0" 1/4" = 1'-0" 0.5
      1/2" = 1'-0" 2
      3/4" = 1'-0" 3
      1"= 1'-0" 4
      1 1/2" = 1'-0" 6
      3" = 1'-0" 12
      Half size 24
      Full size 48
    3/4" = 1'-0" 1/4" = 1'-0" 0.1666
      1/2" = 1'-0" 0.3333
      3/4" = 1'-0" 0.6666
      1"= 1'-0" 1.3333
      1 1/2" = 1'-0" 2
      3" = 1'-0" 4
      Half size 8
      Full size 16

    The formula for calculating the model space scale conversion factor is Main Drawing Plot Scale Factor divided by the Detail Desired Plot Scale Factor.

    Add notes and dimensions after the detail has been inserted into the sheet on which it will appear. To get dimensions to produce the correct sizes on the scaled detail, set the variable DIMLFAC equal to the reciprocal of the conversion factor (that is, 1 divided by the Conversion Factor) prior to doing any dimensioning of the scaled detail. For instance to dimension a detail whose desired scale is 1/2" = 1'-0" inserted into a sheet plotted at 1/8" = 1'-0", set the DIMLFAC at 1/4). To set this variable, at a Command: prompt, type

    dimlfac<RET> [1/conversion factor] <RET>

    Do not forget to change the DIMLFAC back to 1 when you are through dimensioning the detail. Also, remember that since the detail has been scaled, you can no longer directly measure the size of that detail using the DIST command, since it is no longer full size, but some multiple of full size. If you want to calculate the distance, use the DIST command and divide it by the conversion factor.