SketchUp - Changing Dimensions

SketchUp is a nice free program from Google for 3D modeling. It is very intuitive, easy to use for the most of it, however there are still some not that obvious operations like, for example, changing dimensions of different shapes to exact value.

The fist what should be said is that SketchUp model is not driven by dimensions which are setup by "Dimension" tool - those dimensions are just text and arrow objects, so one can click the text and change it to any other text not even related to any dimension. Furthermore, in most cases you really do not want to modify them this way - such a change will kill the possibility of the dimension value to track the true size.

The unpleasant thing about changing dimensions is that it should be done different way for different shapes:

1. For a line segment - right click on it and choose "Entity Info"
   
   Type a new value in the "Length" field, hit "Enter" and that will make the change.


2. For 2D shapes - select a 2D face with "Scale" tool
   
   then select a green box which corresponds to the dimension you are intending to change
   
   
   The "Red Scale" field ("red" indicates that the scaling is along the red coordinate axis) in the right bottom corner of the SketchUp window by default is in scale mode. Just type a new exact dimension with a unit (1m in this example)
   
   
   and press "Enter" - the dimension will change and the value will follow.
   
   
3. For 3D shapes (mostly the same as for 2D case) - with "Select" tool select a whole shape
   
   switch to "Scale" tool
   
   and select a green box corresponding to the dimension you're going to change.
   
   
   Type a new exact dimension with a unit (1m in this example)
   
   
   and press "Enter" - the dimension will get changed.

For more complicated shapes it is easier to create a reference at required position and then modify the shape with "Move", Push/Pull", "Scale" or other tools to align with the reference. A simple line segment, a guide line or a guide point (created with "Tape Measure" or "Protractor") can serve as such a reference.