LayOut Dimension Tools: Dimension types

      NOTICE: SketchUp 2015 is here! When you look at this Knowledge Center article, be sure to pick "SketchUp 2015" from the red box above to see the 2015 version of that content. If there is no version picker, this content applies to all versions of SketchUp.

Dimension types

Introduction

There are two different kinds of "space" in a LayOut document: Paper (2D) Space and Model (3D) Space. LayOut's Linear Dimension tool uses this distinction to correctly dimension the drawing elements on your pages. Understanding Paper Space and Model Space is very important for learning to use the Linear Dimension tool effectively.

Paper (2D) Space

Everything in your LayOut document that isn't inside of a SketchUp model viewport exists in Paper Space. If you draw a rectangle that is 3 inches wide by 2 inches high, its dimension strings will read 3 inches by 2 inches. It is a 2D, graphical element which exists only on the page in LayOut and represents nothing other than itself.

When you use the Linear Dimension tool to dimension an element which is in Paper Space, the resulting dimension shows the actual size of the element on the page. Dimensioning a line which is 6 inches long results in a dimension string that reads 6". See Figure 1.

Figure 1: The title block in this LayOut document is made up of elements which are in Paper Space. Using the Linear Dimension tool on it results in a dimension string that shows the actual length of the dimension line on the page.

Model (3D) Space

Everything inside of a SketchUp model viewport exists in Model Space. Model viewports display SketchUp models which represent objects, buildings and other things that are meant to have an actual, physical size.

When you use the Linear Dimension tool to dimension an element which is in Model Space, the resulting dimension string shows the size of the element in the associated SketchUp model. Figure 2 shows a LayOut document page with a model viewport containing a simple building. Dimensioning the length of the roof ridge results in a dimension string that reads 20' (even though the line on the page is only 5 inches long).

Figure 2: Drawing a dimension between two points on a 3D model in a viewport results in a dimension string that shows the distance in the model.

Special Cases

Mixed-Space Dimensions

When you use the Linear Dimension tool to draw a dimension that connects a point in Paper Space with one in Model Space, the resulting dimension will display in Paper Space. See Figure 3.

Figure 3: Drawing a dimension between a point in a model viewport (Model Space) and a point in Paper Space results in a dimension string that shows the actual length of the dimension line on the page.

Projected Distances

In certain circumstances, LayOut uses a special version of Model Space when you draw a dimension between two points in a SketchUp model viewport. Sometimes, the dimension string you want LayOut to create is different depending on how your model is shown in the viewport. Figure 4 shows a LayOut document page with three viewports; each shows a different view of the same model.

Figure 4: Drawing a dimension between two points in a viewport with perspective turned on (A) results in a dimension string that shows the actual distance in the model. Drawing a dimension between the same two points in an orthographic viewport (B & C) results in a dimension string that gives the projected distance between the two points.

  • Viewport A shows a perspective view of the two buildings.
  • Viewport B shows an orthographic top view.
  • Viewport C shows an orthographic side view.

Drawing a dimension between the tops of both buildings in Viewport A results in a dimension string of 94'-10", which is the actual, diagonal distance between those two points in 3D space. Drawing dimensions between the same two points in Viewports B and C, however, results in dimension strings that show the horizontal distance between them: 80'-0". While this is probably the behavior that most users wish to see, how does LayOut know when to show which distance?

LayOut decides which distance to show based on the camera view associated with the model viewport. It displays the behavior shown in Figure 4 (B and C) only in the following two circumstances:

  1. When the viewport's camera is aligned to one of the Standard Views (Top, Top (Relative), Bottom, Bottom (Relative), Front, Back, Left, Right)
  2. When the viewport is associated with an orthographic Scene where the camera is "aligned" (aimed perpendicular) with an active Section Plane

What's happening under the hood?

Here's what's actually happening when LayOut behaves the way it is in Figure 4, above. When a viewport's camera is set to a standard, orthographic view, or is perpendicular to an active section plane, its dimensions perform a bit of simple arithmetic in order to show the correct dimension string. These dimensions take the Paper Space length of the dimension and multiply it by the drawing scale associated with the viewport to calculate the value of the dimension string.

In Viewport B of Figure 4, the actual length of the dimension line on the page is 4". The drawing scale of the viewport is 1 inch = 20 feet. Doing the math:

4 inches x 20 = 80 feet