I have tested it in many 3d apps but haven't tried it in RF but its is realy simple.
It involes two simple models.
Model 1 is the base modle for your character.
modle two is the black line drawing modle.
Modle 1 is slightly smaller than modle 2 (All verts need to be inside modle2)
Make modle 1 fullbright. Make modle 2 colored jetblack. Then place modle2 right on top of modle one and flip the normals.
You'll get this
![Image](http://www.frogfaith.com/phpbb2/files/cell1_107.jpg)
![Image](http://www.frogfaith.com/phpbb2/files/cell2_360.jpg)
Simple modle so the linse are very corse but it can handle any complexity if RF can handle it.