I believe it's referring to the technique that creates an outline on a 3d object, emulating a 2d animation.
Technically (and this is for 3d apps, Moho may have a different approach), it's looking at the normals on an object, when the normal approaches perpendicular to the camera it renders the associated face as black, giving the impression of an outline, as opposed to rendering the surface. Some toon shaders allow to adjust for the "threshhold" for when the normal turns to an outline. Many times you'll find flickering edges as faces are bordering on the outline threshhold, or large objects suddenly rendering black, for example, as the camera approaches sitting on a table top (the table top approaches perpendicular to the camera), depending on the threshold, it may render the entire table top black.
Some more advanced toon shaders actually draw a line over the faces to create the outline. This is advanatageous as you have faces, defining the path of a line with a definied width. Wild Cat for Maya is one that works this way, using Maya's paint plug-in, for really great results (hmmmm.... can you hear me thinking Lost Marble, would this be possible in a future version of Moho? Is it already doing that, and if so, can we use brushes?)
Many cartoons are using this technique to get 3d integrated into their 2d animations quickly. Some examples include:
-many of the buildings and vehicles in "The Batman" (the new one)
-I believe all of "Gundam SD" is rendered using this technique
It doesn't look much different than a 2d cel, but when it moves you can see the computer precision on the perspective.
I hope this helps (and is correct
)
Kdiddy
