teaching machines

Make a one-sided surface two-sided in Blender

October 16, 2012 by . Filed under public, unity.

I often model things like walls and leaves with only one side. Most computer graphics tools I’ve dealt with only show geometry that faces the viewer. This puts one-sided surfaces in a predicament. When the viewer goes behind them, the geometry disappears.

One simple workaround to this problem is to duplicate your one-sided model and flip its normals to point the reverse direction. Facing one way, the viewer will see one model. Facing the other, the viewer will see the other model. Of course this duplicates geometry and leaves you in a brittle state. If you change the model, you have to change it’s counterpart. Oh, well.

Here’s how you might duplicate and flip in Blender:

  1. Go into Object mode.
  2. Select your model.
  3. Hit Shift-D to duplicate it. Don’t move it. Just hit Escape.
  4. Hit Control-F and choose Flip Normals.
  5. There you go. If you want a visual confirmation that it worked, go to Edit mode, hit N, and turn on the display of normals.


Leave a Reply

Your email address will not be published. Required fields are marked *