You can use this tool to inspect the surfaces of a model. It is a jsfiddle application located here,

Setting up a model in the intersection inspector

  • Go to this jsfiddle editor link Editor You can also select Edit in JSFiddle at the bottom of this page.
  • Select Fork to create your own copy of the application.

  • Set your model sid. Look for the modelSid variable.

  • Run your updated application. You should see your model loaded in the Results pane.

Using the intersection inspector

  • Load the application after you have setup your model.
  • Navigate to the location on the model that you would like to inspect.
  • Place the mouse over the area of interest and stop moving it. You should see a button pop up right over the mouse. If you move the mouse outside the area of the button, it will disappear.

  • Click the button and look at the upper left of the showcase window. You will see the 3D position and normal for the point you clicked.

  • Copy the position and normal text. You can use the position value to set the mattertag anchor position and normal value to set the stem.

Examine the code