Using Inferences to Draw Models in Google SketchUp 8

A big part of using SketchUp’s inference engine involves locking and encouraging inferences — sometimes even simultaneously. When you begin sketching models, these actions seem a little like that thing where you pat your head and rub your stomach at the same time, but with practice, they get easier.

Locking inferences in Google SketchUp

If you hold down the Shift key when you see any of the first four types of linear inferences described previously, that inference gets locked — and stays locked until you release Shift. When you lock an inference, you constrain whatever tool you’re using to work only in the direction of the inference you locked. Confused? Check out the following example for some clarity.

If you want to draw a vertical line that’s exactly as tall as the peak of the house’s roof, here’s what you do:

1. Click once to start drawing an edge.

   
   



2. Move your cursor up until you see the edge you’re drawing turn blue.

   
   

   This is the blue On Axis inference that lets you know you’re exactly parallel to the blue drawing axis.

   
   



3. Hold down the Shift key to lock the inference you see.

   
   

   The edge gets thicker to let you know it’s locked, and now you can draw only in the blue direction (no matter where you move the cursor).

   
   



4. Click the peak of the roof to make your vertical edge end at exactly that height.

   
   



5. Release Shift to unlock the inference.

   
   

Encouraging inferences in Google SketchUp

Sometimes, an inference you need doesn’t show up on its own — when this happens, you have to encourage it. To encourage an inference, just hover your cursor over the part of your model you want to “infer” from and then slowly go back to whatever you were doing when you decided you could use an inference. The following example demonstrates how to encourage an inference.

If you want to start drawing an edge that lines up perfectly with the center of the circle on top of a cylinder but don’t want it to start at the center itself, follow these steps:

1. Hover (don’t click) over the edge of the circle for about two seconds.

   
   



2. Move slowly toward the middle of the circle until the Center Point inference appears.

   
   



3. Hover (still don’t click) over the center point for a couple seconds.

   
   



4. Move your cursor slowly in the direction of where you want to start drawing your edge.

   
   

   A dotted From Point inference appears.

   
   



5. Click to start drawing your edge.

   
   

dummies

Source:http://www.dummies.com/how-to/content/using-inferences-to-draw-models-in-google-sketchup.html